








Preface

This file documents the Revision Control System (RCS).
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.
Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
Copyright © 1982, 1988, 1989 Walter F. Tichy.
Copyright ©  1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
Copyright ©  1996, 1997 Karl Heinz Marbaise (doing converting job)

This manual(Edition 1.1) documents version 5.7
of the Revision Control System (RCS).


-- About the manual --

#AboutAbout the manul. 
#AboutDescInformations about that manual. 
#VersionsVersions of the troff/nroff manuals. 
#BugReportBugs? suggestions? 


-- RCS - A System for Version Control --

#VersionControlRCS -- A System for Version Control. 
#IntroductionIntroduction to RCS. 
#StartRCSGetting started with RCS. 
#IdentificationAutomatic Identification. 
#RevisionTreeThe RCS Revision Tree. 
#BranchesWhen are branches needed?. 
#DeltasRevisions are represented as deltas. 
#ControversialLocking: A Controversial Issue. 
#ConfigurationConfiguration Management. 
#FunctionsRCS Selection Functions. 
#MAKERCSCombining MAKE and RCS. 
#StatisticsUsage Statistics. 
#SurveySurvey of Version Control Tools. 


-- rcsintro - introduction to RCS commands --

#rcsIntroductionIntroduction to RCS commands. 
#rcsintroDescIntroduction to RCS. 
#rcsintroFuncFunctions of RCS. 
#rcsintroStartGetting started with RCS. 
#rcsintroAutoIdentAutomatic identification. 

-- Synopsis of RCS Operations --

#SynopsisSynopsis of RCS Operations. 

-- ci - check in RCS revsisions --

#CheckInci -- check in RCS revsisions. 
#ciIntroIntroduction to ci. 
#ciEnvEnvironment which can change the behaviour of ci and other RCS commands. 
#ciFileModesFile modes. 
#ciFilesFiles. 
#setuid useUsing of uid. 
#ciExamplesExamples. 
#ciDiagDiagnostic output of ci. 
#ciOptionscommand line options of ci. 


-- co - check out RCS revsisions --

#CheckOutco -- check out RCS revsisions 
#coIntroIntroduction to co. 
#coOptionscommand line options of co. 
#coKeywordKeyword expansion and valid keywords. 
#coEnvEnvironment which can change the behaviour of co and other RCS commands. 
#coFileModesFile modes. 
#coFilesFiles. 
#coDiagDiagnostic output of co. 
#coLimitsLimits. 


-- rcs - change RCS file attributes --

#rcsrcs -- change RCS file attributes. 
#rcsIntroIntroduction to rcs. 
#rcsOptionscommand line options of rcs. 
#rcsCompatibilityCompatibility between RCS Versions. 
#rcsFilesFiles. 
#rcsEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsDiagDiagnostic output of rcs. 
#rcsBugsBugs. 


-- ident - identify RCS keyword strings in files --

#identident -- identify RCS keyword strings in files. 
#identIntroIntroduction to rcs. 
#identOptionscommand line options of rcs. 
#identKeywordsKeywords. 


-- rcsclean - clean up working files --

#rcscleanrcsclean -- clean up working files. 
#rcscleanIntroIntroduction to rcsclean. 
#rcscleanOptionscommand line options of rcsclean. 
#rcscleanExamplesExamples in using rcsclean. 
#rcscleanFilesFiles. 
#rcscleanEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcscleanDiagDiagnostic output of rcsclean. 
#rcscleanBugsBugs. 


-- rcsdiff -- compare RCS revisions --

#rcsdiffrcsdiff -- compare RCS revisions. 
#rcsdiffIntroIntroduction to rcsdiff. 
#rcsdiffOptionscommand line options of rcsdiff. 
#rcsdiffExamplesExamples in using rcsdiff. 
#rcsdiffEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsdiffDiagDiagnostic output of rcsdiff. 


-- rcsmerge -- merge RCS versions --

#rcsmergercsmerge -- merge RCS versions. 
#rcsmergeIntroIntroduction to rcs. 
#rcsmergeOptionscommand line options of rcs. 
#rcsmergeExamplesExamples of rcsmerge. 
#rcsmergeEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsmergeDiagDiagnostic output of rcs. 


-- rlog -- print log messages and other information about RCS files --

#rlogrlog -- print log messages and other information about RCS files. 
#rlogIntroIntroduction to rlog. 
#rlogOptionscommand line options of rlog. 
#rlogExamplesExamples. 
#rlogEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rlogDiagDiagnostic output of rlog. 
#rlogBugsBugs. 


-- merge -- three-way file merge --

#mergemerge -- three-way file merge. 
#mergeIntroIntroduction to merge. 
#mergeOptionscommand line options of merge. 
#mergeDiagDiagnostic output of merge. 
#mergeBugsBugs. 


------------ Appendencies ------------


-- Appendix A --

#AppendixAFormat of RCS file. 


-- Appendix B --

#AppendixBBooks and related manuals. 
#FeldmanGNU - Make. 
#HuntGNU - diff. 
#RochkindSCCS. 
#TichyDesign and implementation of RCS. 
#LeblangComputer-Aided Software Engineering. 
#GlasserThe Evolution of a Source Code Control System. 
#BrownThe Clear/Caster System. 
#HabermannA Software Development Control System. 
#DECCode Management System. 
#LampsonPractical Use of a Polymorphic Applicative Language. 
#Tichy1A Data Model for Programming Support Environments and its Application. 
#HeckelA Technique for Isolating Differences Between Files. 
#Tichy2The String-to-String Correction Problem with Block Moves. 

#IndexConcept Index. 


About the manual 



#AboutDescInformations about that manual. 
#VersionsVersions of the troff/nroff manuals. 
#BugReportBugs? suggestions? 


Description 

These 'Texinfo' files are hand converted out of the
troff/nroff files, which came with the RCS system.
This has done by hand, cause there does not exist a converter
which is able to convert (nroff/troff) into GNU's 'Texinfo' format
(I know one, which is able to do the other way,'texinfo' to nroff).
The main reason for doing such a stupid work was, to have the opinion
to convert the 'Texinfo' into OS/2-IPF format.
This conversion is done with "Texinfo converting Tools Release 1.00"
which are able to convert to OS/2-IPF format and HTML(not the Perl-script).
The next possibility is to get a well printed manual, using
TeX(I use emTeX myself).
This is the first Edition of this manuals, so don't be angry about
the cryptic node names within the 'Texinfo' files.
That's the only way to have unique node names for alle command line options.
And by the way this is the only way to make references to command line
options of every command.
The next thing is to make this manual a little more readable, that means
not to double subsection with command line options on every command
(rlog, rcs, rcsdiff, ···).
The way out of this dilemma is to discribe these options within
a chapter 'overall options' or 'global options' which can be used on every
command(rlog, rcs, rcsdiff···).
But this will be done in the next edition, if you like it.
If you like to make a printed manual yourself, you have to TeX it with
the 'texinfo' macro package(V2.185), it also works with
version 2.150 of the package. It should also work with edition 2 of the
'Texinfo' macro package.

Versions 

If you found newer versions of troff/nroff manual then please mail to me.
Here are the exact RCS--versions of the troff/roff pages for
checking:


Identification of the "RCS -- A System for Version Control"

manual part (rcs.ms):

$Id: rcs.ms,v 5.4 1995/06/01 16:23:43 eggert Exp $

Identification of the ci manual part(ci.1):


$Id: ci.1,v 5.17 1995/06/16 06:19:24 eggert Exp $

Identification of the co manual part(co.1):


$Id: co.1,v 5.13 1995/06/01 16:23:43 eggert Exp $

Identification of the rcs manual part(rcs.1):


$Id: rcs.1,v 5.13 1995/06/05 08:28:35 eggert Exp $

Identification of the ident manual part(ident.1):


$Id: ident.1,v 5.4 1993/11/09 17:40:15 eggert Exp $

Identification of the rcsclean manual part(rcsclean.1):


$Id: rcsclean.1,v 1.12 1993/11/03 17:42:27 eggert Exp $

Identification of the rcsdiff  manual part(rcsdiff.1):


$Id: rcsdiff.1,v 5.5 1993/11/03 17:42:27 eggert Exp $

Identification of the rcsmerge  manual part(rcsmerge.1):


$Id: rcsmerge.1,v 5.6 1995/06/01 16:23:43 eggert Exp $

Identification of the rlog manual part(rlog.1):


$Id: rlog.1,v 5.9 1995/06/16 06:19:24 eggert Exp $

Identification of the merge manual part(merge.1):


$Id: merge.1,v 5.7 1995/06/01 16:23:43 eggert Exp $





Bugs?, suggestions? 

If you think you have found a bug within this manual, you could write
by electronic mail a report.
Also, if you have suggestions for this manual.
Changes of chapters, sections and so on.
Do you have good examples for this manual?
Or what else you like.
Please write to me:

Karl Heinz Marbaise
KHMarbaise@p69.ks.fido.de
Fido-Net: 2:2452/117.69


RCS--A System for Version Control 

Walter F. Tichy
Department of Computer Sciences
Purdue University
West Lafayette, Indiana 47907
An important problem in program development and maintenance is
version control, i.e., the task of keeping a software system
consisting of many versions and configurations well organized.
The Revision Control System (RCS) is a software tool that assists
with that task. RCS manages revisions of text documents, in
particular source programs, documentation, and test data. It
automates the storing, retrieval, logging and identification of
revisions, and it provides selection mechanisms for composing
configurations. This paper introduces basic version control
concepts and discusses the practice of version control using RCS.
For conserving space, RCS stores deltas, i.e., differences
between successive revisions.  Several delta storage methods are
discussed. Usage statistics show that RCS's delta storage method
is space and time efficient. The paper concludes with a detailed
survey of version control tools.
Keywords: configuration management, history management,
version control, revisions, deltas.
An earlier version of this paper was published in
Software--Practice & Experience, 7 (July 1985), 637-654.

#IntroductionIntroduction to RCS. 
#StartRCSGetting started with RCS. 
#IdentificationAutomatic Identification. 
#RevisionTreeThe RCS Revision Tree. 
#BranchesWhen are branches needed?. 
#DeltasRevisions are represented as deltas. 
#ControversialLocking: A Controversial Issue. 
#ConfigurationConfiguration Management. 
#FunctionsRCS Selection Functions. 
#MAKERCSCombining MAKE and RCS. 
#StatisticsUsage Statistics. 
#SurveySurvey of Version Control Tools. 


Introduction 

Version control is the task of keeping software systems
consisting of many versions and configurations well organized.
The Revision Control System (RCS) is a set of UNIX commands that
assist with that task.
RCS' primary function is to manage revision groups. A
revision group is a set of text documents, called 
revisions,
that evolved from each other. A new revision is created by
manually editing an existing one. RCS organizes the revisions
into an ancestral tree.  The initial revision is the root of the
tree, and the tree edges indicate from which revision a given one
evolved. Besides managing individual revision groups, RCS
provides flexible selection functions for composing
configurations. RCS may be combined with MAKE (See 
#FeldmanFeldman ),
resulting in a powerful package for version control.
RCS also offers facilities for merging updates with customer
modifications, for distributed software development, and for
automatic identification. Identification is the 
stamping
of revisions and configurations with unique markers. These
markers are akin to serial numbers, telling software maintainers
unambiguously which configuration is before them.
RCS is designed for both production and experimental
environments. In production environments, access controls detect
update conflicts and prevent overlapping changes. In experimental
environments, where strong controls are counterproductive, it is
possible to loosen the controls.
Although RCS was originally intended for programs, it is useful
for any text that is revised frequently and whose previous
revisions must be preserved.  RCS has been applied successfully
to store the source text for drawings, VLSI layouts,
documentation, specifications, test data, form letters and
articles.
This paper discusses the practice of version control using RCS.
It also introduces basic version control concepts, useful for
clarifying current practice and designing similar systems.
Revision groups of individual components are treated in the next
three sections, and the extensions to configurations follow.
Because of its size, a survey of version control tools appears at
the end of the paper.

Getting started with RCS 

Suppose a text file f.c is to be placed under control of
RCS. Invoking the check-in command

ci  f.c

creates a new revision group with the contents of f.c as
the initial revision (numbered 1.1) and stores the group into the
file 
f.c,v. Unless told otherwise, the command deletes
f.c. It also asks for a description of the group. The
description should state the common purpose of all revisions in
the group, and becomes part of the group's documentation. All
later check-in commands will ask for a log entry, which should
summarize the changes made. (The first revision is assigned a
default log message, which just records the fact that it is the
initial revision.)
Files ending in ,v are called RCS files
(
v stands for Rersions); the others are called working
files. To get back the working file 
f.c in the previous
example, execute the check-out command:

co  f.c

This command extracts the latest revision from the revision group
f.c,v and writes it into f.c. The file f.c
can now be edited and, when finished, checked back in with
ci:

ci  f.c

Ci assigns number 1.2 to the new revision.
If 
ci complains with the message

ci error: no lock set by <login>

then the system administrator has decided to configure RCS for a
production environment by enabling the 
strict locking
feature
. If this feature is enabled, all RCS files are
initialized such that check-in operations require a lock on the
previous revision (the one from which the current one evolved).
Locking prevents overlapping modifications if several people work
on the same file. If locking is required, the revision should
have been locked during the check-out by using the option
-l:

co -l  f.c

Of course it is too late now for the check-out with locking,
because 
f.c has already been changed; checking out the
file again would overwrite the modifications. (To prevent
accidental overwrites, 
co senses the presence of a working
file and asks whether the user really intended to overwrite it.
The overwriting check-out is sometimes useful for backing up to
the previous revision.) To be able to proceed with the check-in
in the present case, first execute

rcs  -l  f.c

command retroactively locks the latest revision, unless someone
else locked it in the meantime.  In this case, the two
programmers involved have to negotiate whose modifications should
take precedence.
If an RCS file is private, i.e., if only the
owner of the file is expected to deposit revisions into it, the
strict locking feature is unnecessary and may be disabled. If
strict locking is disabled, the owner of the RCS file need not
have a lock for check-in. For safety reasons, all others still
do.  Turning strict locking off and on is done with the commands:

rcs  -U  f.c   and rcs  -L  f.c

These commands enable or disable the strict locking feature for each
RCS file individually. The system administrator only decides
whether strict locking is enabled initially.
To reduce the clutter in a working directory, all RCS files can
be moved to a subdirectory with the name 
RCS. RCS commands
look first into that directory for RCS files. All the commands
presented above work with the 
RCS
subdirectory
#fn1(1) Pairs of RCS and working files can actually
be specified in 3 ways: a) both are given, b) only the working
file is given, c) only the RCS file is given. If a pair is given,
both files may have arbitrary path prefixes; RCS commands pair
them up intelligently
. without change.
It may be undesirable that ci deletes the working file.
For instance, sometimes one would like
to save the current revision, but continue editing. Invoking

ci  -l  f.c

checks in f.c as usual, but performs an additional
check-out with locking afterwards.  Thus, the working file does
not disappear after the check-in. Similarly, the option 
-u
does a check-in followed by a check-out without locking.  This
option is useful if the file is needed for compilation after the
check-in. Both options update the identification markers in the
working file (see below).
Besides the operations ci and co, RCS provides the
following commands:
ident

extract identification markers
rcs

change RCS file attributes
rcsclean

remove unchanged working files (optional)
rcsdiff

compare revisions
rcsfreeze

record a configuration (optional)
rcsmerge

merge revisions
rlog

read log messages and other information in RCS files


A synopsis of these commands appears in the Appendix.

Automatic Identification 

RCS can stamp source and object code with special identification
strings, similar to product and serial numbers. To obtain such
identification, place the marker

$Id$

into the text of a revision, for instance inside a comment.
The check-out operation will replace this marker with a string of the form

$Id:  filename  revisionnumber  date  time  author state  locker $

This string need never be touched, because co keeps it
up to date automatically. To propagate the marker into object code,
simply put it into a literal character string.
In C, this is done as follows:

static char rcsid[] = "$Id$";

The command ident extracts such markers from any file,
in particular from object code.
Ident helps to find out which revisions of which modules
were used in a given program. It returns a complete and unambiguous
component list, from which a copy of the program can be reconstructed.
This facility is invaluable for program maintenance.
There are several additional identification markers, one for each component
of $Id$. The marker

$Log$

has a similar function.  It accumulates
the log messages that are requested during check-in.
Thus, one can maintain the complete history of a revision directly inside it,
by enclosing it in a comment.
Figure 1 is an edited version of a log contained in revision 4.1 of
the file 
ci.c.  The log appears at the beginning of the file,
and makes it easy to determine what the recent modifications were.

/*
 * $Log: ci.c,v $
 * Revision 4.1  1983/05/10 17:03:06  wft
 * Added option -d and -w, and updated assignment of date, etc.
 * to new delta. Added handling of default branches.
 *
 * Revision 3.9  1983/02/15 15:25:44  wft
 * Added call to fastcopy() to copy remainder of RCS file.
 *
 * Revision 3.8  1983/01/14 15:34:05  wft
 * Added ignoring of interrupts while new RCS file is renamed;
 * avoids deletion of RCS files by interrupts.
 *
 * Revision 3.7  1982/12/10 16:09:20  wft
 * Corrected checking of return code from diff.
 * An RCS file now inherits its mode during the first ci from the
 * working file, except that write permission is removed.
 */

Figure 1.  Log entries produced by the marker $Log$
Since revisions are stored in the form of differences, each log
message is physically stored once, independent of the number of
revisions present. Thus, the $Log$ marker incurs
negligible space overhead.

The RCS Revision Tree 

RCS arranges revisions in an ancestral tree. The ci
command builds this tree; the auxiliary command 
rcs prunes
it. The tree has a root revision, normally numbered 1.1, and
successive revisions are numbered 1.2, 1.3, etc.  The first field
of a revision number is called the 
release number and the
second one the 
level number.  Unless given explicitly, the
ci command assigns a new revision number by incrementing
the level number of the previous revision. The release number
must be incremented explicitly, using the 
-r option of
ci. Assuming there are revisions 1.1, 1.2, and 1.3 in the
RCS file 
f.c,v, the command

ci  -r2.1  f.c       or       ci  -r2  f.c

assigns the number 2.1 to the new revision. Later check-ins
without the 
-r option will assign the numbers 2.2, 2.3,
and so on. The release number should be incremented only at major
transition points in the development, for instance when a new
release of a software product has been completed.

When are branches needed? 

A young revision tree is slender: It consists of only one branch,
called the trunk. As the tree ages, side branches may form.
Branches are needed in the following 4 situations.

Temporary fixes


Suppose a tree has 5 revisions grouped in 2 releases, as
illustrated in Figure 2. Revision 1.3, the last one of release 1,
is in operation at customer sites, while release 2 is in active
development.

+-----+     +-----+     +-----+     +-----+     +-----+
! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->>
+-----+     +-----+     +-----+     +-----+     +-----+


Figure 2.  A slender revision tree.
Now imagine a customer requesting a fix of a problem in revision
1.3, although actual development has moved on to release 2.  RCS
does not permit an extra revision to be spliced in between 1.3
and 2.1, since that would not reflect the actual development
history.  Instead, create a branch at revision 1.3, and check in
the fix on that branch. The first branch starting at 1.3 has
number 1.3.1, and the revisions on that branch are numbered
1.3.1.1, 1.3.1.2, etc. The double numbering is needed to allow
for another branch at 1.3, say 1.3.2. Revisions on the second
branch would be numbered 1.3.2.1, 1.3.2.2, and so on. The
following steps create branch 1.3.1 and add revision 1.3.1.1:

co -r1.3 f.c     -- check out revision 1.3
edit f.c         -- change it
ci  -r1.3.1  f.c -- check it in on branch 1.3.1

This sequence of commands transforms the tree of Figure 2 into
the one in Figure 3. Note that it may be necessary to incorporate
the differences between 1.3 and 1.3.1.1 into a revision at level
2.  The operation 
rcsmerge automates this process (see the
Appendix).

+-----+     +-----+     +-----+     +-----+     +-----+
! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->>
+-----+     +-----+     +--+--+     +-----+     +-----+
                           !
                           !        +---------+
                           +------->! 1.3.1.1 !---->>
                                    +---------+

Figure 3.  A revision tree with one side branch
Distributed development and customer modifications

Assume a situation as in Figure 2, where revision 1.3 is in
operation at several customer sites, while release 2 is in
development. Customer sites should use RCS to store the
distributed software. However, customer modifications should not
be placed on the same branch as the distributed source; instead,
they should be placed on a side branch. When the next software
distribution arrives, it should be appended to the trunk of the
customer's RCS file, and the customer can then merge the local
modifications back into the new release. In the above example, a
customer's RCS file would contain the following tree, assuming
that the customer has received revision 1.3, added his local
modifications as revision 1.3.1.1, then received revision 2.4,
and merged 2.4 and 1.3.1.1, resulting in 2.4.1.1.

    +-----+                 +-----+
--->! 1.3 !---------------->! 2.4 !---->>
    +--+--+                 +---+-+
       !                        !
       !     +---------+        !       +---------+
       +---->! 1.3.1.1 !        +------>! 2.4.1.1 !
             +---------+                +---------+

Figure 4.  A customer's revision tree with local modifications.
This approach is actually practiced in the CSNET project, where
several universities and a company cooperate in developing a
national computer network.
Parallel development

Sometimes it is desirable to explore an alternate design or
a different implementation technique in parallel with the
main line development.  Such development
should be carried out on a side branch.
The experimental changes may later be moved into the main line, or abandoned.
Conflicting updates

A common occurrence is that one programmer has checked out a
revision, but cannot complete the assignment for some reason.  In
the meantime, another person must perform another modification
immediately.  In that case, the second person should check-out
the same revision, modify it, and check it in on a side branch,
for later merging.
Every node in a revision tree consists of the following
attributes: a revision number, a check-in date and time, the
author's identification, a log entry, a state and the actual
text.  All these attributes are determined at the time the
revision is checked in. The state attribute indicates the status
of a revision. It is set automatically to `experimental' during
check-in. A revision can later be promoted to a higher status,
for example `stable' or `released'.  The set of states is
user-defined.




Revisions are represented as deltas 

For conserving space, RCS stores revisions in the form of deltas,
i.e., as differences between revisions. The user interface
completely hides this fact.
A delta is a sequence of edit commands that transforms one string
into another.  The deltas employed by RCS are line-based, which
means that the only edit commands allowed are insertion and
deletion of lines. If a single character in a line is changed,
the edit scripts consider the entire line changed. The program
diff produces a small, line-based delta between pairs of
text files. A character-based edit script would take much longer
to compute, and would not be significantly shorter.
Using deltas is a classical space-time tradeoff: deltas reduce
the space consumed, but increase access time. However, a version
control tool should impose as little delay as possible on
programmers. Excessive delays discourage the use of version
controls, or induce programmers to take shortcuts that compromise
system integrity. To gain reasonably fast access time for both
editing and compiling, RCS arranges deltas in the following way.
The most recent revision on the trunk is stored intact. All other
revisions on the trunk are stored as reverse deltas. A reverse
delta describes how to go backward in the development history: it
produces the desired revision if applied to the successor of that
revision. This implementation has the advantage that extraction
of the latest revision is a simple and fast copy operation.
Adding a new revision to the trunk is also fast: 
ci simply
adds the new revision intact, replaces the previous revision with
a reverse delta, and keeps the rest of the old deltas. Thus,
ci requires the computation of only one new delta.
Branches need special treatment.  The naive solution would be to
store complete copies for the tips of all branches. Clearly, this
approach would cost too much space.  Instead, RCS uses
forward deltas for branches.  Regenerating a revision on a
side branch proceeds as follows.  First, extract the latest
revision on the trunk; secondly, apply reverse deltas until the
fork revision for the branch is obtained; thirdly, apply forward
deltas until the desired branch revision is reached.  Figure 5
illustrates a tree with one side branch.  Triangles pointing to
the left and right(with five exclamation marks) represent
reverse and forward deltas,
respectively.

      !           !           !           !           !
+-----!     +-----!     +-----!     +-----!     +-----!
! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->>
+-----+     +-----!     +--+--!     +-----!     +-----!
      !           !        !  !           !           !
                           !
                           !            !               !
                           !  +---------!     +---------!
                           +->! 1.3.1.1 !---->! 1.3.1.2 !
                              +---------!     +---------!
                                        !               !

Figure 3.  A revision tree with one side branch
Although implementing fast check-out for the latest trunk
revision, this arrangement has the disadvantage that generation
of other revisions takes time proportional to the number of
deltas applied.  For example, regenerating the branch tip in
Figure 5 requires application of five deltas (including the
initial one).  Since usage statistics show that the latest trunk
revision is the one that is retrieved in 95 per cent of all cases
(see the section on usage statistics), biasing check-out time in
favor of that revision results in significant savings. However,
careful implementation of the delta application process is
necessary to provide low retrieval overhead for other revisions,
in particular for branch tips.
There are several techniques for delta application. The naive one
is to pass each delta to a general-purpose text editor. A
prototype of RCS invoked the UNIX editor 
ed both for
applying deltas and for expanding the identification markers.
Although easy to implement, performance was poor, owing to the
high start-up costs and excess generality of 
ed.  An
intermediate version of RCS used a special-purpose,
stream-oriented editor. This technique reduced the cost of
applying a delta to the cost of checking out the latest trunk
revision.  The reason for this behavior is that each delta
application involves a complete pass over the preceding revision.
However, there is a much better algorithm.  Note that the deltas
are line oriented and that most of the work of a stream editor
involves copying unchanged lines from one revision to the next. A
faster algorithm avoids unnecessary copying of character strings
by using a 
piece table. A piece table is a one-dimensional
array, specifying how a given revision is 
pieced-together
from lines in the RCS file. Suppose piece table 
PTr
represents revision 
r. Then PTr[i] contains the
starting position of line 
i of revision r.
Application of the next delta transforms piece table 
PTr
into 
PTr+1.  For instance, a delete command removes a
series of entries from the piece table.  An insertion command
inserts new entries, moving the entries following the insertion
point further down the array.  The inserted entries point to the
text lines in the delta. Thus, no I/O is involved except for
reading the delta itself. When all deltas have been applied to
the piece table, a sequential pass through the table looks up
each line in the RCS file and copies it to the output file,
updating identification markers at the same time. Of course, the
RCS file must permit random access, since the copied lines are
scattered throughout that file.  Figure 6 illustrates an RCS file
with two revisions and the corresponding piece tables.
The piece table approach has the property that the time for
applying a single delta is roughly determined by the size of the
delta, and not by the size of the revision.  For example, if a
delta is 10 per cent of the size of a revision, then applying it
takes only 10 per cent of the time to generate the latest trunk
revision.  (The stream editor would take 100 per cent.)
There is an important alternative for representing deltas that
affects performance.  
SCCS, a precursor of RCS, uses
interleaved deltas. A file containing interleaved deltas
is partitioned into blocks of lines. Each block has a header that
specifies to which revision(s) the block belongs.  The blocks are
sorted out in such a way that a single pass over the file can
pick up all the lines belonging to a given revision.  Thus, the
regeneration time for all revisions is the same: all headers must
be inspected, and the associated blocks either copied or skipped.
As the number of revisions increases, the cost of retrieving any
revision is much higher than the cost of checking out the latest
trunk revision with reverse deltas.  A detailed comparison of
SCCS's interleaved deltas and RCS's reverse deltas can be
found in Reference 4. This reference considers the version of RCS
with the stream editor only.  The piece table method improves
performance further, so that RCS is always faster than SCCS,
except if 10 or more deltas are applied.
Additional speed-up for both delta methods can be obtained by
caching the most recently generated revision, as has been
implemented in 
DSEE With caching, access time to
frequently used revisions can approach normal file access time,
at the cost of some additional space.

Locking: A Controversial Issue 

The locking mechanism for RCS was difficult to design. The
problem and its solution are first presented in their 
pure
form, followed by a discussion of the complications caused by
real-world considerations.
RCS must prevent two or more persons from depositing competing
changes of the same revision. Suppose two programmers check out
revision 2.4 and modify it.  Programmer A checks in a revision
before programmer 
B. Unfortunately, programmer B has not seen
A's changes, so the effect is that A's changes are covered up by
B's deposit. A's changes are not lost since all revisions are
saved, but they are confined to a single revision
#fn2(2) Note
that this problem is entirely different from the atomicity
problem. Atomicity means that concurrent update operations on the
same RCS file cannot be permitted, because that may result in
inconsistent data. Atomic updates are essential (and implemented
in RCS), but do not solve the conflict discussed here.
.
This conflict is prevented in RCS by locking. Whenever someone
intends to edit a revision (as opposed to reading or compiling
it), the revision should be checked out and locked, using the
-l option on co.  On subsequent check-in, ci
tests the lock and then removes it. At most one programmer at a
time may lock a particular revision, and only this programmer may
check in the succeeding revision. Thus, while a revision is
locked, it is the exclusive responsibility of the locker.
An important maxim for software tools like RCS is that they must
not stand in the way of making progress with a project. This
consideration leads to several weakenings of the locking
mechanism. First of all, even if a revision is locked, it can
still be checked out.  This is necessary if other people wish to
compile or inspect the locked revision while the next one is in
preparation.  The only operations they cannot do are to lock the
revision or to check in the succeeding one.  Secondly, check-in
operations on other branches in the RCS file are still possible;
the locking of one revision does not affect any other revision.
Thirdly, revisions are occasionally locked for a long period of
time because a programmer is absent or otherwise unable to
complete the assignment.  If another programmer has to make a
pressing change, there are the following three alternatives for
making progress:

find out who is holding the lock and ask that person to release it;


check out the locked revision, modify it, check it

in on a branch, and merge the changes later;
break the lock.  Breaking a lock leaves a highly visible

trace, namely an electronic mail message that is sent
automatically to the holder of the lock, recording the breaker
and a commentary requested from him. Thus, breaking locks is
tolerated under certain circumstances, but will not go unnoticed.
Experience has shown that the automatic mail message attaches a
high enough stigma to lock breaking, such that programmers break
locks only in real emergencies, or when a co-worker resigns and
leaves locked revisions behind.



If an RCS file is private, i.e., when a programmer owns an RCS
file and does not expect anyone else to perform check-in
operations, locking is an unnecessary nuisance. In this case, the
strict locking feature discussed earlier may be disabled,
provided that file protection is set such that only the owner may
write the RCS file. This has the effect that only the owner can
check-in revisions, and that no lock is needed for doing so.
As added protection, each RCS file contains an access list that
specifies the users who may execute update operations.  If an
access list is empty, only normal UNIX file protection applies.
Thus, the access list is useful for restricting the set of people
who would otherwise have update permission.  Just as with
locking, the access list has no effect on read-only operations
such as 
co.  This approach is consistent with the UNIX
philosophy of openness, which contributes to a productive
software development environment.

Configuration Management 

The preceding sections described how RCS deals with
revisions of individual components; this section discusses how to
handle configurations. A configuration is a set of revisions,
where each revision comes from a different revision group, and
the revisions are selected according to a certain criterion. For
example, in order to build a functioning compiler, the `right'
revisions from the scanner, the parser, the optimizer and the
code generator must be combined. 
RCS, in conjunction with
MAKE, provides a number of facilities to effect a smooth
selection.

RCS Selection Functions 


Default selection


During development, the usual selection criterion is to choose
the latest revision of all components.  The 
co command
makes this selection by default.  For example, the command

co  *,v

retrieves the latest revision on the default branch of each RCS
file in the current directory. The default branch is usually the
trunk, but may be set to be a side branch. Side branches as
defaults are needed in distributed software development, as
discussed in the section on the RCS revision tree.
Release based selection

Specifying a release or branch number selects the latest revision
in that release or branch. For instance,

co  -r2  *,v

retrieves the latest revision with release number 2 from each RCS
file. This selection is convenient if a release has been
completed and development has moved on to the next release.
State and author based selection

If the highest level number within a given release number is not
the desired one, the state attribute can help.  For example,

co  -r2  -sReleased  *,v

retrieves the latest revision with release number 2 whose state
attribute is `Released'. Of course, the state attribute has to be
set appropriately, using the 
ci or rcs commands.
Another alternative is to select a revision by its author, using
the 
-w option.
Date based selection

Revisions may also be selected by date. Suppose a release of an
entire system was completed and current on March 4, at 1:00 p.m.
local time.  Then the command

co  -d'March 4, 1:00 pm LT'  *,v

checks out all the components of that release, independent of the
numbering. The 
-d option specifies a `cutoff date', i.e.,
the revision selected has a check-in date that is closest to, but
not after the date given.
Name based selection

The most powerful selection function is based on assigning
symbolic names to revisions and branches. In large systems, a
single release number or date is not sufficient to collect the
appropriate revisions from all groups. For example, suppose one
wishes to combine release 2 of one subsystem and release 15 of
another. Most likely, the creation dates of those releases differ
also. Thus, a single revision number or date passed to the
co command will not suffice to select the right revisions.
Symbolic revision numbers solve this problem. Each RCS file may
contain a set of symbolic names that are mapped to numeric
revision numbers.  For example, assume the symbol 
V3 is
bound to release number 2 in file 
s,v, and to revision
number 15.9 in 
t,v. Then the single command

co  -rV3  s,v  t,v

retrieves the latest revision of release 2 from s,v, and
revision 15.9 from 
t,v. In a large system with many
modules, checking out all revisions with one command greatly
simplifies configuration management.
Judicious use of symbolic revision numbers helps with organizing
large configurations.
A special command, rcsfreeze, assigns a symbolic revision
number to a selected revision in every RCS file. 
rcsfreeze
effectively freezes a configuration. The assigned symbolic
revision number selects all components of the configuration. If
necessary, symbolic numbers may even be intermixed with numeric
ones.  Thus, 
V3.5 in the above example would select
revision 2.5 in 
s,v and branch 15.9.5 in t,v.
The options -r, -s, -w and -d may be
combined.  If a branch is given, the latest revision on that
branch satisfying all conditions is retrieved; otherwise, the
default branch is used.




Combining MAKE and RCS 

MAKE ( #FeldmanFeldman ) is a program that processes
configurations. It is driven by configuration specifications
recorded in a special file, called a `Makefile'. MAKE avoids
redundant processing steps by comparing creation dates of source
and processed objects. For example, when instructed to compile
all modules of a given system, it only recompiles those source
modules that were changed since they were processed last.
MAKE has been extended with an auto-checkout
feature
#fn3(3) This auto-checkout extension is available only
in some versions of MAKE, e.g. GNU MAKE.
 for RCS.* When a
certain file to be processed is not present, MAKE attempts a
check-out operation. If successful, MAKE performs the required
processing, and then deletes the checked out file to conserve
space. The selection parameters discussed above can be passed to
MAKE either as parameters, or directly embedded in the Makefile.
MAKE has also been extended to search the subdirectory named
RCS for needed files, rather than just the current working
directory. However, if a working file is present, MAKE totally
ignores the corresponding RCS file and uses the working file. (In
newer versions of MAKE distributed by AT&T and others,
auto-checkout can be achieved with the rule DEFAULT, instead of a
special extension of MAKE. However, a file checked out by the
rule DEFAULT will not be deleted after processing.
Rcsclean can be used for that purpose.)
With auto-checkout, RCS/MAKE can effect a selection rule
especially tuned for multi-person software development and
maintenance. In these situations, programmers should obtain
configurations that consist of the revisions they have personally
checked out plus the latest checked in revision of all other
revision groups. This schema can be set up as follows.
Each programmer chooses a working directory and places into it a
symbolic link, named 
RCS, to the directory containing the
relevant RCS files. The symbolic link makes sure that 
co
and 
ci operations need only specify the working files, and
that the Makefile need not be changed. The programmer then checks
out the needed files and modifies them. If MAKE is invoked, it
composes configurations by selecting those revisions that are
checked out, and the rest from the subdirectory 
RCS. The
latter selection may be controlled by a symbolic revision number
or any of the other selection criteria. If there are several
programmers editing in separate working directories, they are
insulated from each other's changes until checking in their
modifications.
Similarly, a maintainer can recreate an older configuration by
starting to work in an empty working directory. During the
initial MAKE invocation, all revisions are selected from RCS
files. As the maintainer checks out files and modifies them, a
new configuration is gradually built up. Every time MAKE is
invoked, it substitutes the modified revisions into the
configuration being manipulated.
A final application of RCS is to use it for storing Makefiles.
Revision groups of Makefiles represent multiple versions of
configurations. Whenever a configuration is baselined or
distributed, the best approach is to unambiguously fix the
configuration with a symbolic revision number by calling
rcsfreeze, to embed that symbol into the Makefile, and to
check in the Makefile (using the same symbolic revision number).
With this approach, old configurations can be regenerated easily
and reliably.

Usage Statistics 

The following usage statistics were collected on two DEC
VAX-11/780 computers of the Purdue Computer Science Department.
Both machines are mainly used for research purposes.  Thus, the
data reflect an environment in which the majority of projects
involve prototyping and advanced software development, but
relatively little long-term maintenance.
For the first experiment, the ci and co operations
were instrumented to log the number of backward and forward
deltas applied. The data were collected during a 13 month period
from Dec. 1982 to Dec. 1983. Table I summarizes the results.

Oper.  !   Total  !Total deltas!mean deltas! Operations  !Branch 
       !operations!   applied  !  applied  !with >1 delta!operations
-------+----------+------------+-----------+-------------+----------
co     !     7867 !    9320    !    1.18   !   509 (6%)  ! 203 (3%)
ci     !     3468 !    2207    !    0.64   !    85 (2%)  !  75 (2%)
ci & co!    11335 !   11527    !    1.02   !   594 (5%)  ! 278 (2%)
 
 
Table I.  Statistics for co and ci operations

The first two lines show statistics for check-out and check-in;
the third line shows the combination. Recall that 
ci
performs an implicit check-out to obtain a revision for computing
the delta. In all measures presented, the most recent revision
(stored intact) counts as one delta.  The number of deltas
applied represents the number of passes necessary, where the
first `pass' is a copying step.
Note that the check-out operation is executed more than twice as
frequently as the check-in operation. The fourth column gives the
mean number of deltas applied in all three cases. For 
ci,
the mean number of deltas applied is less than one. The reasons
are that the initial check-in requires no delta at all, and that
the only time 
ci requires more than one delta is for
branches. Column 5 shows the actual number of operations that
applied more than one delta. The last column indicates that
branches were not used often.
The last three columns demonstrate that the most recent trunk
revision is by far the most frequently accessed. For RCS,
check-out of this revision is a simple copy operation, which is
the absolute minimum given the copy-semantics of 
co.
Access to older revisions and branches is more common in
non-academic environments, yet even if access to older deltas
were an order of magnitude more frequent, the combined average
number of deltas applied would still be below 1.2. Since RCS is
faster than SCCS until up to 10 delta applications, reverse
deltas are clearly the method of choice. .PP The second
experiment, conducted in March of 1984, involved surveying the
existing RCS files on our two machines.  The goal was to
determine the mean number of revisions per RCS file, as well as
the space consumed by them. Table II shows the results. (Tables I
and II were produced at different times and are unrelated.)

          !Total RCS!  Total  !Mean     !Means size!Mean size!Overhead
          ! files   !revisions!revisions!RCS files !revisions!
----------+---------+---------+---------+----------+---------+--------
All Files !    8033 !   11133 !   1.39  !   6156   !  5585   !  1.10
Files with!    1477 !    4578 !   3.10  !   8074   !  6041   !  1.34
>= 2 delta!         !         !         !          !         !
 
 
Table II. Statistics for RCS files

The mean number of revisions per RCS file is 1.39.
Columns 5 and 6 show the mean
sizes (in bytes) of an RCS file and of the latest revision of
each RCS file, respectively. The `overhead' column contains the
ratio of the mean sizes. Assuming that all revisions in an RCS
file are approximately the same size, this ratio gives a measure
of the space consumed by the extra revisions.
In our sample, over 80 per cent of the RCS files contained only a
single revision. The reason is that our systems programmers
routinely check in all source files on the distribution tapes,
even though they may never touch them again. To get a better
indication of how much space savings are possible with deltas,
all measures with those files that contained 2 or more revisions
were recomputed.  Only for those files is RCS necessary. As shown
in the second line, the average number of revisions for those
files is 3.10, with an overhead of 1.34. This means that the
extra 2.10 deltas require 34 per cent extra space, or 16 per cent
per extra revision. Rochkind(
#RochkindRochkind ) measured the space
consumed by SCCS, and reported an average of 5 revisions per
group and an overhead of 1.37 (or about 9 per cent per extra
revision). In a later paper, Glasser (
#GlasserGlasser ) observed an
average of 7 revisions per group in a single, large project, but
provided no overhead figure. In his paper on DSEE , Leblang
(
#LeblangLeblang ) reported that delta storage combined with blank
compression results in an overhead of a mere 1-2 per cent per
revision. Since leading blanks accounted for about 20 per cent of
the surveyed Pascal programs, a revision group with 5-10 members
was smaller than a single cleartext copy.
The above observations demonstrate clearly that the space needed
for extra revisions is small.  With delta storage, the luxury of
keeping multiple revisions online is certainly affordable. In
fact, introducing a system with delta storage may reduce storage
requirements, because programmers often save back-up copies
anyway.  Since back-up copies are stored much more efficiently
with deltas, introducing a system such as RCS may actually free a
considerable amount of space.

Survey of Version Control Tools 

The need to keep back-up copies of software arose when programs
and data were no longer stored on paper media, but were entered
from terminals and stored on disk. Back-up copies are desirable
for reliability, and many modern editors automatically save a
back-up copy for every file touched. This strategy is valuable
for short-term back-ups, but not suitable for long-term version
control, since an existing back-up copy is overwritten whenever
the corresponding file is edited.
Tape archives are suitable for long-term, offline storage. If all
changed files are dumped on a back-up tape once per day, old
revisions remain accessible.  However, tape archives are
unsatisfactory for version control in several ways.  First,
backing up the file system every 24 hours does not capture
intermediate revisions. Secondly, the old revisions are not
online, and accessing them is tedious and time-consuming. In
particular, it is impractical to compare several old revisions of
a group, because that may require mounting and searching several
tapes. Tape archives are important fail-safe tools in the event
of catastrophic disk failures or accidental deletions, but they
are ill-suited for version control. Conversely, version control
tools do not obviate the need for tape archives.
A natural technique for keeping several old revisions online is
to never delete a file. Editing a file simply creates a new file
with the same name, but with a different sequence number. This
technique, available as an option in DEC's VMS operating system,
turns out to be inadequate for version control. First, it is
prohibitively expensive in terms of storage costs, especially
since no data compression techniques are employed. Secondly,
indiscriminately storing every change produces too many
revisions, and programmers have difficulties distinguishing them.
The proliferation of revisions forces programmers to spend much
time on finding and deleting useless files. Thirdly, most of the
support functions like locking, logging, revision selection, and
identification described in this paper are not available.
An alternative approach is to separate editing from revision
control. The user may repeatedly edit a given revision, until
freezing it with an explicit command. Once a revision is frozen,
it is stored permanently and can no longer be modified. (In RCS,
freezing a revisions is done with 
ci.) Editing a frozen
revision implicitly creates a new one, which can again be changed
repeatedly until it is frozen itself. This approach saves exactly
those revisions that the user considers important, and keeps the
number of revisions manageable. IBM's CLEAR/CASTER (
#BrownBrown ),
AT&T's SCCS (
#RochkindRochkind ), CMU's SDC ( #HabermannHabermann ), and
DEC's CMS (
#DECDEC ), are examples of version control systems
using this approach. CLEAR/CASTER maintains a data base of
programs, specifications, documentation and messages, using
deltas. Its goal is to provide control over the development
process from a management viewpoint. SCCS stores multiple
revisions of source text in an ancestral tree, records a log
entry for each revision, provides access control, and has
facilities for uniquely identifying each revision. An efficient
delta technique reduces the space consumed by each revision
group. SDC is much simpler than SCCS because it stores not more
than two revisions.  However, it maintains a complete log for all
old revisions, some of which may be on back-up tape. CMS, like
SCCS, manages tree-structured revision groups, but offers no
identification mechanism.
Tools for dealing with configurations are still in a state of
flux. SCCS, SDC and CMS can be combined with MAKE or MAKE-like
programs. Since flexible selection rules are missing from all
these tools, it is sometimes difficult to specify precisely which
revision of each group should be passed to MAKE for building a
desired configuration. The Xerox Cedar system (
#LampsonLampson )
provides a `System Modeller' that can rebuild a configuration
from an arbitrary set of module revisions. The revisions of a
module are only distinguished by creation time, and there is no
tool for managing groups. Since the selection rules are
primitive, the System Modeller appears to be somewhat tedious to
use. Apollo's DSEE (
#LeblangLeblang ) is a sophisticated software
engineering environment. It manages revision groups in a way
similar to SCCS and CMS. Configurations are built using
`configuration threads'. A configuration thread states which
revision of each group named in a configuration should be chosen.
A configuration thread may contain dynamic specifiers (e.g.,
`choose the revisions I am currently working on, and the most
recent revisions otherwise'), which are bound automatically at
build time. It also provides a notification mechanism for
alerting maintainers about the need to rebuild a system after a
change.
RCS is based on a general model for describing
multi-version/multi-configuration systems (
#Tichy1Tichy1 ). The
model describes systems using AND/OR graphs, where AND nodes
represent configurations, and OR nodes represent version groups.
The model gives rise to a suit of selection rules for composing
configurations, almost all of which are implemented in RCS. The
revisions selected by RCS are passed to MAKE for configuration
building. Revision group management is modelled after SCCS. RCS
retains SCCS's best features, but offers a significantly simpler
user interface, flexible selection rules, adequate integration
with MAKE and improved identification. A detailed comparison of
RCS and SCCS appears in Reference 4.
An important component of all revision control systems is a
program for computing deltas. SCCS and RCS use the program
diff ( #RochkindRochkind ), which first computes the longest
common substring of two revisions, and then produces the delta
from that substring. The delta is simply an edit script
consisting of deletion and insertion commands that generate one
revision from the other.
A delta based on a longest common substring is not necessarily
minimal, because it does not take advantage of crossing block
moves. Crossing block moves arise if two or more blocks of lines
(e.g., procedures) appear in a different order in two revisions.
An edit script derived from a longest common substring first
deletes the shorter of the two blocks, and then reinserts it.
Heckel (
#HeckelHeckel ) proposed an algorithm for detecting block
moves, but since the algorithm is based on heuristics, there are
conditions under which the generated delta is far from minimal.
DSEE uses this algorithm combined with blank compression,
apparently with satisfactory overall results. A new algorithm
that is guaranteed to produce a minimal delta based on block
moves appears in Reference 13. A future release of RCS will use
this algorithm.

Acknowledgements:
Many people have helped make RCS a success by contributed
criticisms, suggestions, corrections, and even whole new commands
(including manual pages). The list of people is too long to be
reproduced here, but my sincere thanks for their help and
goodwill goes to all of them.


Introduction to RCS commands 




#rcsintroDescIntroduction to RCS. 
#rcsintroFuncFunctions of RCS. 
#rcsintroStartGetting started with RCS. 
#rcsintroAutoIdentAutomatic identification. 


Description 

The  Revision  Control System (RCS) manages multiple revisions
of files.  RCS  automates  the  storing,  retrieval,
logging, identification, and merging of revisions.  RCS is
useful for text that is revised  frequently,  for  example
programs,  documentation,  graphics, papers, and form letters.
The basic user interface is extremely simple.  The  novice
only  needs  to  learn two commands: 
ci and co.
ci, short for "check in", deposits the contents of a file into
an archival file called an RCS file.
An RCS file contains all revisions of a particular file.
co, short for  "check out",
retrieves revisions from an RCS file.

Functions of RCS 


Store and retrieve multiple revisions of text.  RCS saves

all old revisions in a space  efficient  way. Changes no longer
destroy the original, because the previous revisions  remain
accessible.   Revisions can  be  retrieved  according to ranges
of revision numbers,  symbolic  names,  dates,   authors,   and
states.
Maintain  a  complete history of changes.  RCS logs all

changes automatically.   Besides  the  text  of each  revision,
RCS stores the author, the date and time of check-in, and a log
message summarizing the change.  The logging makes it easy to
find out what happened to a module,  without  having  to  compare
source listings or having to track down colleagues.
Resolve access conflicts.  When two  or  more  programmers

wish  to  modify  the  same revision, RCS alerts the programmers
and prevents  one  modification from corrupting the other.
Maintain  a  tree  of  revisions.  RCS can maintain

separate lines of development for each module.   It stores  a
tree structure that represents the ancestral relationships among
revisions.
Merge revisions and resolve conflicts.   Two  separate

lines  of development of a module can be coalesced by merging.
If the revisions to  be  merged affect  the  same  sections of
code, RCS alerts the user about the overlapping changes.
Control releases and configurations.  Revisions can be

assigned symbolic names and marked as released, stable,
experimental, etc.  With these  facilities, configurations  of
modules can be described simply and directly.
Automatically identify  each  revision  with  name,

revision  number,  creation time, author, etc.  The
identification is like a stamp that can be embedded at  an
appropriate place in the text of a revision. The identification
makes  it  simple  to  determine which  revisions  of  which
modules make up a given configuration.
Minimize secondary storage.  RCS needs little extra space

for the revisions (only the differences).  If intermediate
revisions are deleted, the corresponding deltas are compressed
accordingly.




Getting Started with RCS 

Suppose  you  have  a  file 
f.c that you wish to put under
control of RCS.  If you have not already done so, make  an
RCS directory with the command

mkdir  RCS

Then invoke the check-in command

ci  f.c

This  command  creates  an  RCS file in the RCS directory,
stores 
f.c into it as revision 1.1, and deletes
f.c.   It also  asks  you for a description.
The description should be a synopsis of the contents
of  the  file.   All  later check-in  commands  will
ask  you  for a log entry, which should summarize the
changes that you made.
Files in the RCS directory are called RCS files; the  others
are  called  working  files.  To get back the working
file f.c in the previous example, use the  check-out  command

co  f.c

This  command  extracts  the  latest revision from the RCS
file and writes it into 
f.c.  If you want to edit f.c,
you must lock it as you check it out with the command

co  -l  f.c

You can now edit f.c.
Suppose  after  some editing you want to know what changes
that you have made.  The command

rcsdiff  f.c

tells  you  the  difference  between  the  most   recently
checked-in  version  and  the working file.  You can check
the file back in by invoking

ci  f.c

This increments the revision number properly.
If ci complains with the message

ci error: no lock set by 
your name

then you have tried to check in a file even though you did
not lock it when you checked it out.  Of course, it is too
late now to do the check-out with locking, because another
check-out  would  overwrite  your modifications.  Instead,
invoke

rcs  -l  f.c

This command will lock the latest revision for you, unless
somebody  else  got  ahead  of you already.  In this case,
you'll have to negotiate with that person.
Locking assures that you, and only you, can check  in  the
next  update,  and avoids nasty problems if several people
work on the same file.  Even if a revision is  locked,  it
can still be checked out for reading, compiling, etc.  All
that locking prevents is a 
check-in  by  anybody  but  the
locker.
If  your  RCS  file  is private, i.e., if you are the only
person who is going to deposit revisions into  it,  strict
locking  is not needed and you can turn it off.  If strict
locking is turned off, the owner of the RCS file need  not
have  a  lock  for check-in; all others still do.  Turning
strict locking off and on is done with the commands

rcs  -U  f.c     and     rcs  -L  f.c

If you don't want to clutter your working  directory  with
RCS  files, create a subdirectory called RCS in your work-
ing directory, and move all your  RCS  files  there.   RCS
commands  will  look  first  into  that  directory to find
needed files.  All the commands discussed above will still
work,  without  any modification.  (Actually, pairs of RCS
and working files can be specified in three ways: (a) both
are  given,  (b)  only the working file is given, (c) only
the RCS file is given.  Both RCS  and  working  files  may
have  arbitrary  path  prefixes; RCS commands pair them up
intelligently.)
To avoid the deletion of the working file during  check-in
(in  case  you  want  to  continue  editing or compiling),
invoke

ci  -l  f.c     or     ci  -u  f.c

These commands check in  f.c  as  usual,  but  perform  an
implicit check-out.  The first form also locks the checked
in revision, the second one doesn't.  Thus, these  options
save  you one check-out operation.  The first form is useful
if you want to continue editing, the second one if you
just  want  to read the file.  Both update the identification
markers in your working file (see below).
You can give ci the number you want assigned to a  checked
in revision.  Assume all your revisions were numbered 1.1,
1.2, 1.3, etc., and you would like  to  start  release  2.
The command

ci  -r2  f.c     or     ci  -r2.1  f.c

assigns the number 2.1 to the new revision.  From then on,
ci will number the subsequent  revisions  with  2.2,  2.3,
etc.  The corresponding co commands

co  -r2  f.c     and     co  -r2.1  f.c

retrieve the latest revision numbered 2.x and the revision
2.1, respectively.  co without a revision  number  selects
the  latest  revision on the 
trunk, i.e. the highest revision
with a number consisting of two fields.  Numbers with
more  than  two fields are needed for branches.  For example,
to start a branch at revision 1.3, invoke

ci  -r1.3.1  f.c

This command starts a branch numbered 1 at  revision  1.3,
and  assigns  the number 1.3.1.1 to the new revision.  For
more information about branches, see 
#rcsOptbrcsOptb .

Automatic Identification 

RCS can put special strings for identification  into  your
source  and  object  code.  To obtain such identification,
place the marker

$Id$

into your text, for instance inside a comment.   RCS  will
replace this marker with a string of the form

$Id:  filename revision date time author state $

With such a marker on the first page of each  module,  you
can  always  see with which revision you are working.  RCS
keeps the markers up to date automatically.  To  propagate
the  markers  into  your object code, simply put them into
literal character strings.  In C, this is done as follows:

static char rcsid[] = "$Id$";

The  command  ident  extracts  such markers from any file,
even object code and dumps.  Thus, ident lets you find out
which revisions of which modules were used in a given program.
You may also find it useful to put the marker  $Log$  into
your  text, inside a comment.  This marker accumulates the
log messages that are requested  during  check-in.   Thus,
you  can  maintain  the  complete  history  of  your  file
directly inside it.  There are several additional  identification
markers; see 
#coKeywordcoKeyword  for details.

Synopsis of RCS Operations 


ci -- check in revisions


Ci stores the contents of a working file into the
corresponding RCS file as a new revision.
If the RCS file doesn't exist, 
ci creates it.
Ci removes the working file, unless one of the options
-u or -l is present.
For each check-in, 
ci asks for a commentary
describing the changes relative to the previous revision.
Ci assigns the revision number given by the -r option;
if that option is missing, it derives the number from the
lock held by the user; if there is no lock and locking is not strict,
ci increments the number of the latest revision on the trunk.
A side branch can only be started by explicitly specifying its
number with the 
-r option during check-in.
Ci also determines whether the revision to be checked in is
different from the previous one, and asks whether to proceed if not.
This facility simplifies check-in operations for large systems,
because one need not remember which files were changed.
The option -k searches the checked in file for identification
markers containing the attributes
revision number, check-in date, author and state, and assigns these
to the new revision rather than computing them.  This option is
useful for software distribution: Recipients of distributed software
using RCS should check in updates with the 
-k option.
This convention guarantees that revision numbers, check-in dates,
etc., are the same at all sites.
co -- check out revisions

Co retrieves revisions according to revision number,
date, author and state attributes.  It either places the revision
into the working file, or prints it on the standard output.
Co always expands the identification markers.
ident -- extract identification markers

Ident extracts the identification markers expanded by co
from any file and prints them.
rcs -- change RCS file attributes

Rcsis an administrative operation that changes access lists,
locks, unlocks, breaks locks, toggles the strict-locking feature,
sets state attributes and symbolic revision numbers, changes the
description, and deletes revisions.  A revision can
only be deleted if it is not the fork of a side branch.
rcsclean -- clean working directory

Rcsclean removes working files that were checked out but never changed.
#fn4(4) The rcsclean and rcsfreeze commands are optional
and are not always installed.

rcsdiff -- compare revisions

Rcsdiff compares two revisions and prints their
difference, using the UNIX tool 
diff.
One of the revisions compared may be checked out.
This command is useful for finding out about changes.
rcsfreeze -- freeze a configuration

Rcsfreeze assigns the same symbolic revision number
to a given revision in all RCS files.
This command is useful for accurately recording a configuration.
rcsmerge -- merge revisions

Rcsmerge merges two revisions, rev1 and rev2,
with respect to a common ancestor.
A 3-way file comparison determines the segments of lines that
are (a) the same in all three revisions, or (b) the same in 2 revisions,
or (c) different in all three.  For all segments of type (b) where
rev1 is the differing revision,
the segment in 
rev1 replaces the corresponding segment of rev2.
Type (c) indicates an overlapping change, is flagged as an error, and requires user
intervention to select the correct alternative.
rlog -- read log messages

Rlog prints the log messages and other information in an RCS file.




ci -- check in RCS revisions 




#ciIntroIntroduction to ci. 
#ciOptionscommand line options of ci. 
#ciFileNamingFile naming. 
#ciExamplesExamples. 
#ciFileModesFile modes. 
#ciFilesFiles. 
#setuid useUsing of uid. 
#ciEnvEnvironment which can change the behaviour of ci and other RCS commands. 
#ciDiagDiagnostic output of ci. 


ci description 

ci stores new revisions into RCS files. Each pathname
matching an RCS suffix is taken to be an RCS file. All others are
assumed to be working files containing new revisions. 
ci
deposits the contents of each working file into the corresponding
RCS file. If only a working file is given, 
ci tries to
find the corresponding RCS file in an RCS subdirectory and then
in the working file's directory. For more details, See 
#ciFileNamingciFileNaming 
below.
For ci to work, the caller's login must be on the access
list, except if the access list is empty or the caller is the
superuser or the owner of the file. To append a new revision to
an existing branch, the tip revision on that branch must be
locked by the caller.  Otherwise, only a new branch can be
created.  This restriction is not enforced for the owner of the
file if non-strict locking is used (see 
#rcsrcs ). A lock held
by someone else can be broken with the 
rcs command.
Unless the -f option is given, ci checks whether
the revision to be deposited differs from the preceding one. If
not, instead of creating a new revision 
ci reverts to the
preceding one. To revert, ordinary 
ci removes the working
file and any lock; 
ci -l keeps and ci -u
removes any lock, and then they both generate a new working file
much as if 
co -l or co -u had been applied to
the preceding revision. When reverting, any 
-n and
-s options apply to the preceding revision.
For each revision deposited, ci prompts for a log message.
The log message should summarize the change and must be
terminated by end-of-file or by a line containing 
. by
itself. If several files are checked in 
ci asks whether to
reuse the previous log message. If the standard input is not a
terminal, 
ci suppresses the prompt and uses the same log
message for all files(Option 
-m of ci, #ciOptmciOptm ).
If the RCS file does not exist, ci creates it and deposits
the contents of the working file as the initial revision (default
number: 
1.1 ). The access list is initialized to empty.
Instead of the log message,
ci requests descriptive text
(Option 
-t of ci, #ciOpttciOptt )
below).
The number rev of the deposited revision can be given by any
of the options 
-f, -i, -I, -j,
-k, -l, -M, -q, -r or -u
rev can be symbolic, numeric, or mixed.
Symbolic names in
rev must already be defined;
see the Option 
-n ( #ciOptnciOptn ) and -N ( #ciOptNuciOptNu )
options for assigning names during checkin.
If rev is $, ci determines the revision
number from keyword values in the working file.
If rev begins with a period, then the default branch
(normally the trunk) is prepended to it. If 
rev is a
branch number followed by a period, then the latest revision on
that branch is used.
If rev is a revision number, it must be higher than the
latest one on the branch to which 
rev belongs, or must
start a new branch.
If rev is a branch rather than a revision number, the new
revision is appended to that branch.  The level number is
obtained by incrementing the tip revision number of that branch.
If 
rev indicates a non-existing branch, that branch is
created with the initial revision numbered 
rev .1.
If rev is omitted, ci tries to derive the new
revision number from the caller's last lock.  If the caller has
locked the tip revision of a branch, the new revision is appended
to that branch. The new revision number is obtained by
incrementing the tip revision number. If the caller locked a
non-tip revision, a new branch is started at that revision by
incrementing the highest branch number at that revision. The
default initial branch and level numbers are 
1..
If rev is omitted and the caller has no lock, but owns the
file and locking is not set to  
strict, then the revision
is appended to the default branch (normally the trunk; see the
option 
-b of rcs #rcsOptbrcsOptb ).
Exception: On the trunk, revisions can be appended to the end, but
not inserted.

Command line options of ci 

Overview off all options which can be given to
Synopsis: ci [options] file ···
ci.

#ciOptr-r Revision 
#ciOptl-l lock a revision. 
#ciOptu-u unlock a revision. 
#ciOptf-f force a deposit. 
#ciOptk-k search for keyword values. 
#ciOptq-q quiet mode 
#ciOpti-i initial 
#ciOptj-j just check in 
#ciOptIu-I interacitve mode 
#ciOptd-d date 
#ciOptMu-M 
#ciOptm-m log message 
#ciOptn-n symbolic name 
#ciOptNu-N replace an existing symbolic name 
#ciOpts-s set state 
#ciOptt-t discription 
#ciOptTu-T modification time 
#ciOptw-w login 
#ciOptV-V Version of RCS; Emulate RCS Version 
#ciOptx-x Suffixes 
#ciOptz-z Time zoone for output. 


Check in revision 



-rrev


Check in revision 
rev.
-r

The bare -r option (without any revision) has an unusual
meaning in 
ci. With other RCS  commands, a bare -r
option specifies the most recent revision on the default branch,
but with 
ci, a bare -r option reestablishes the
default behavior of releasing a lock and removing the working
file, and is used to override any default 
-l or -u
options established by shell aliases or scripts.



lock a revision 



-l[rev]


works like 
-r, except it performs an additional
co-l for the deposited revision.  Thus, the
deposited revision is immediately checked out again and
locked. This is useful for saving a revision although
one wants to continue editing it after the checkin.



unlock a revision 



-u[rev]


works like 
-l, except that the deposited revision is not
locked. This lets one read the working file immediately after
checkin.
The -l, bare -r, and -u options are mutually
exclusive and silently override each other. For example, 
ci
-u -r
 is equivalent to ci -r because bare -r
overrides 
-u.



force a deposit 



-f[rev]


forces a deposit; the new revision is deposited even it is not
different from the preceding one.



keyword values 



-k[rev]


searches the working file for keyword values to determine its
revision number, creation date, state, and author (see
#CheckOutCheckOut ), and assigns these values to the deposited
revision, rather than computing them locally. It also generates a
default login message noting the login of the caller and the
actual checkin date. This option is useful for software
distribution.  A revision that is sent to several sites should be
checked in with the 
-k option at these sites to preserve
the original number, date, author, and state. The extracted
keyword values and the default log message can be overridden with
the options 
-d, -m, -s, -w, and any
option that carries a revision number.



quiet 




-q[rev]


quiet mode; diagnostic output is not printed. A revision that is
not different from the preceding one is not deposited, unless
-f is given.



initial check in 



-i[rev]


initial checkin; report an error if the RCS file already exists.
This avoids race conditions in certain applications.



just check in 



-j[rev]


just checkin and do not initialize;
report an error if the RCS file does not already exist.



interactive mode 




-I[rev]


interactive mode; the user is prompted and questioned
even if the standard input is not a terminal.



date 



-d[date]


uses 
date for the checkin date and time. The date
is specified in free format as explained in 
co (See #CheckOutCheckOut ).
This is useful for lying about the checkin date, and for 
-k if
no date is available. If 
date is empty, the working file's
time of last modification is used.



modification time 



-M[rev]


Set the modification time on any new working file to be the date
of the retrieved revision. For example, 
ci -d -M -u f does
not alter 
f 's modification time, even if f's
contents change due to keyword substitution. Use this option with
care; it can confuse 
MAKE.



log message 



-m[msg]


uses the string 
msg as the log message for all revisions
checked in. By convention, log messages that start with 
#
are comments and are ignored by programs like GNU Emacs's
vc package. Also, log messages that start with
{ clumpname } (followed by white space) are meant to be
clumped together if possible, even if they are associated with
different files; the 
{ clumpname } label is used only
for clumping, and is not considered to be part of the log message
itself.



symbolic name 




-n[name]


assigns the symbolic name 
name to the number of the
checked-in revision. 
ci prints an error message if
name is already assigned to another number.



replace symbolic name 



-N[name]


same as 
-n, except that it overrides a previous assignment
of 
name.



states 



-s[state]


sets the state of the checked-in revision to the identifier
state. The default state is Exp.



description 




-tfile


writes descriptive text from the contents of the named
file
into the RCS file, deleting the existing text.
The 
file cannot begin with -.
-t-string

Write descriptive text from the string into the RCS file,
deleting the existing text.
The -t option, in both its forms, has effect only during
an initial checkin; it is silently ignored otherwise.
During the initial checkin, if -t is not given, ci
obtains the text from standard input, terminated by end-of-file
or by a line containing 
. by itself. The user is prompted
for the text if interaction is possible; see optiom 
-I
of 
ci(See #ciOptIuciOptIu ).
For backward compatibility with older versions of RCS, a bare
-t option is ignored.



modification time 



-T


Set the RCS file's modification time to the new revision's time
if the former precedes the latter and there is a new revision;
preserve the RCS file's modification time otherwise. If you have
locked a revision, 
ci usually updates the RCs file's
modification time to the current time, because the lock is stored
in the RCS file and removing the lock requires changing the RCS
file. This can create an RCS file newer than the working file in
one of two ways: first, 
ci -M can create a working file
with a date before the current time; second, when reverting to
the previous revision the RCS file can change while the working
file remains unchanged. These two cases can cause excessive
recompilation caused by a 
MAKE dependency of the working
file on the RCS file. The 
-T option inhibits this
recompilation by lying about the RCS file's date. Use this option
with care; it can suppress recompilation even when a checkin of
one working file should affect another working file associated
with the same RCS file. For example, suppose the RCS file's time
is 01:00, the (changed) working file's time is 02:00, some other
copy of the working file has a time of 03:00, and the current
time is 04:00. Then 
ci -d -T sets the RCS file's time to
02:00 instead of the usual 04:00; this causes 
MAKE to
think (incorrectly) that the other copy is newer than the RCs
file.



login 



-wlogin


uses 
login for the author field of the deposited revision.
Useful for lying about the author, and for 
-k if no author
is available.



version and emulation 




-V


Print RCS's version number.
-Vn

Emulate RCS version n. See #coOptVcoOptV 



suffixes 



-xsuffixes


specifies the suffixes for RCS files. A nonempty suffix matches
any pathname ending in the suffix. An empty suffix matches any
pathname of the form 
RCS/path or
path1/RCS/path2. The -x option can specify a list
of suffixes separated by 
. For example, -x,v/
specifies two suffixes: 
,v and the empty suffix. If two or
more suffixes are specified, they are tried in order when looking
for an RCS file; the first one that works is used for that file.
If no RCS file is found but an RCS file can be created, the
suffixes are tried in order to determine the new RCS file's name.
The default for 
suffixes is installation-dependent;
normally it is 
,v/ for hosts like Unix that permit commas
in filenames, and is empty (i.e. just the empty suffix) for other
hosts.



time zoone 





-zzoone


specifies the date output format in keyword substitution, and
specifies the default time zone for 
date in the
-ddate option. The zoone should be empty, a
numeric UTC offset, or the special string 
LT for local
time. The default is an empty 
zoone, which uses the
traditional RCS format of UTC without any time zone indication and
with slashes separating the parts of the date; otherwise, times
are output in ISO 8601 format with time zone indication. For
example, if local time is January 11, 1990, 8pm Pacific Standard
Time, eight hours west of UTC, then the time is output as
follows:

Option   time output
-z       1990/01/11 04:00:00       (default)
-zLT     1990-01-11 20:00:00-0800
-z+0530  1990-01-11 09:30:00+0530

This option
does not affect dates stored in RCS files, which are always UTC.



FILE NAMING 

Pairs of RCS files and working files can be specified in three
ways (see also the example section).

Both the file and the working file are given.

The RCS pathname is of the form 
path1/workfileX
and the working pathname is of the form
path2/workfile where path1/ and path2/
are (possibly different or empty) paths, 
workfile
is a filename, and 
X is an RCs suffix. If X
is empty, 
path1/ must start with RCS/ or
must contain 
/RCS/.
Only the RCS file is given.  Then the working file is created

in the current directory and its name is derived from the name of
the RCS file by removing 
path1/ and the suffix X.
Only the working file is given. Then ci considers each

RCS suffix 
X in turn, looking for an RCS file of the form
path2/RCS/workfileX or (if the former is not found and
X is nonempty) path2/workfileX.



If the RCS file is specified without a path in 1) and 2),
ci looks for the RCS file first in the directory
./RCS and then in the current directory.
ci reports an error if an attempt to open an RCS file
fails for an unusual reason, even if the RCS file's pathname is
just one of several possibilities. For example, to suppress use
of RCS commands in a directory 
d , create a regular file
named 
d/RCS so that casual attempts to use RCS commands in
d fail because d/RCS is not a directory.

Examples 

Suppose ,v is an RCS suffix and the current directory
contains a subdirectory 
RCS with an RCS file
io.c,v. Then each of the following commands check in a
copy of 
io.c into RCS/io.c,v as the latest
revision, removing 
io.c.

ci  io.c
ci  RCS/io.c,v
ci  io.c,v
ci  io.c RCS/io.c,v
ci  io.c io.c,v
ci  RCS/io.c,v  io.c
ci  io.c,v  io.c

Suppose instead that the empty suffix is an RCS suffix and the
current directory contains a subdirectory 
RCS with an RCS
file 
io.c. The each of the following commands checks in a
new revision.

ci  io.c
ci  RCS/io.c
ci  io.c  RCS/io.c
ci  RCS/io.c  io.c


File Modes 

An RCS file created by ci inherits the read and execute
permissions from the working file.  If the RCS file exists
already, 
ci preserves its read and execute permissions.
ci always turns off all write permissions of RCS files.

Files 

Temporary files are created in the directory containing the
working file, and also in the temporary directory (See 
#ciEnvciEnv 
under 
#coEnvcoEnv ). A semaphore file or files
are created in the directory containing the RCS file. With a
nonempty suffix, the semaphore names begin with the first
character of the suffix; therefore, do not specify an suffix
whose first character could be that of a working filename. With
an empty suffix, the semaphore names end with 
_ so working
filenames should not end in 
_
ci never changes an RCS or working file. Normally,
ci unlinks the file and creates a new one; but instead of
breaking a chain of one or more symbolic links to an RCS file, it
unlinks the destination file instead. Therefore, 
ci breaks
any hard or symbolic links to any working file it changes; and
hard links to RCS files are ineffective, but symbolic links to
RCS files are preserved.
The effective user must be able to search and write the directory
containing the RCS file. Normally, the real user must be able to
read the RCS and working files and to search and write the
directory containing the working file; however, some older hosts
cannot easily switch between real and effective users, so on
these hosts the effective user is used for all accesses. The
effective user is the same as the real user unless your copies of
ci and co have setuid privileges. As described in
the next section, these privileges yield extra security if the
effective user owns all RCS files and directories, and if only
the effective user can write RCS directories.
Users can control access to RCS files by setting the permissions
of the directory containing the files; only users with write
access to the directory can use RCS commands to change its RCS
files. For example, in hosts that allow a user to belong to
several groups, one can make a group's RCS directories writable
to that group only. This approach suffices for informal projects,
but it means that any group member can arbitrarily change the
group's RCS files, and can even remove them entirely. Hence more
formal projects sometimes distinguish between an RCS
administrator, who can change the RCS files at will, and other
project members, who can check in new revisions but cannot
otherwise change the RCS files.

Setuid use 

To prevent anybody but their RCS administrator from deleting revisions,
a set of users can employ setuid privileges as follows.

Check that the host supports RCS setuid use.

Consult a trustworthy expert if there are any doubts.
It is best if the 
seteuid
system call works as described in Posix 1003.1a Draft 5,
because RCS can switch back and forth easily
between real and effective users, even if the real user is
root.
If not, the second best is if the 
setuid
system call supports saved setuid
(the 
_POSIX_SAVED_IDS behavior of Posix 1003.1-1990);
this fails only if the real or effective user is
root.
If RCS detects any failure in setuid, it quits immediately.
Choose a user A

to serve as RCS administrator for the set of users.
Only 
A can invoke the rcs
command on the users' RCS files.
A should not be root
or any other user with special powers.
Mutually suspicious sets of users should use different administrators.
Choose a pathname B to be a directory of files to

be executed by the users.
Have A set up B to contain copies of

ci and co that are setuid to A
by copying the commands from their standard installation directory
D as follows:

mkdir 
B
cp 
D/c[io] B
chmod go-w,u+s 
B/c[io]

Have each user prepend B to their path as follows:


PATH=
B:$PATH; export PATH # ordinary shell
set path=(
B $path)        # C - shell

Have A create each RCS directory R

with write access only to 
A
as follows:

mkdir 
R
chmod go-w 
R

If you want to let only certain users read the RCS files,

put the users into a group 
G,
and have 
A further protect the RCs directory as follows:

chgrp 
G  R
chmod g-w, o-rwx  
R

Have A copy old RCS files (if any) into

R, to ensure that A owns them.
An RCS file's access list limits who can check in and lock revisions.

The default access list is empty,
which grants checkin access to anyone who can read the RCS file.
If you want limit checkin access,
have 
A invoke rcs -a on the file; see #rcsrcs 
In particular, 
rcs -e -aA limits access to just
A.
Have A initialize any new RCS files with

rcs -i before initial checkin, adding the
-a option if you want to limit checkin access.
Give setuid privileges only to ci, co,

and 
rcsclean; do not give them to rcs
or to any other command.
Do not use other setuid commands to invoke RCS commands;

setuid is trickier than you think!




Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
A backslash escapes spaces within an option.
The 
RCSINIT options are prepended to the argument lists
of most RCS commands. Useful 
RCSINIT
options include 
-q, -V, -x and -z.
TMPDIR

Name of the temporary directory.
If not set, the environment variables
TMP and TEMP
are inspected instead and the first value found is taken;
if none of them are set,
a host-dependent default is used, typically
/tmp.



Diagnostics 

For each revision, ci prints the RCS file,
the working file, and the number of both the deposited and the
preceding revision. The exit status is zero if and only if all
operations were successful.

co -- check out RCS revisions 




#coIntroIntroduction to co. 
#coOptionscommand line options of co. 
#coKeywordKeyword expansion and valid keywords. 
#coFileModesFile modes. 
#coFilesFiles. 
#coEnvEnvironment which can change the behaviour of co and other RCS commands. 
#coDiagDiagnostic output of co. 
#coLimitsLimits. 


co description 

co retrieves a revision from each RCS file and stores it
into the corresponding working file.
Pathnames matching an RCS suffix denote RCS files; all others
denote working files. Names are paired as explained in
#ciIntrociIntro .Revisions of an RCS file can be checked out locked or unlocked.
Locking a revision prevents overlapping updates.  A revision
checked out for reading or processing (e.g., compiling) need not
be locked.  A revision checked out for editing and later checkin
must normally be locked.  Checkout with locking fails if the
revision to be checked out is currently locked by another user.
(A lock can be broken with 
rcs #rcsrcs ). Checkout with
locking also requires the caller to be on the access list of the
RCS file, unless he is the owner of the file or the superuser,
or the access list is empty. Checkout without locking is not
subject to accesslist restrictions, and is not affected by the
presence of locks.
A revision is selected by options for revision or branch number,
checkin date/time, author, or state. When the selection options
are applied in combination, 
co retrieves the latest
revision that satisfies all of them. If none of the selection
options is specified, 
co retrieves the latest revision on
the default branch (normally the trunk, see the 
-b option
of 
#rcsrcs ). A revision or branch number can be attached to any
of the options  
-f, -I, -l, -M,
-p, -q, -r or -u. The options
-d (date), -s(state), and -w (author)
retrieve from a single branch, the 
selected branch, which
is either specified by one of 
-f, ···, -u, or
the default branch.
A co command applied to an RCS file with no revisions
creates a zero-length working file. 
co always performs
keyword substitution (see below).

Command line options of co 

Overview off all options which can be given to co
Synopsis: co [options] file ···

#coOptr-r Revision 
#coOptl-l lock a revision. 
#coOptu-u unlock a revision. 
#coOptf-f Force overwriting working file 
#coOptk-k Keyword strings; Substitution and so on. 
#coOptp-p Output to standard out. 
#coOptq-q Quiet mode. 
#coOptI-I Interactive mode. 
#coOptd-d Check out by date/time. 
#coOptM-M Modification time. 
#coOpts-s set state. 
#coOptT-T preserve Modification time. 
#coOptw-w check out by user. 
#coOptj-j Joining revisions. 
#coOptV-V Version; Emulation of RCS Version. 
#coOptx-x Suffixes. 
#coOptz-z Time zone. 


Check out revision 



-rrev


retrieves the latest revision whose number is less than or equal
to 
rev. If rev indicates a branch rather than a
revision, the latest revision on that branch is retrieved. If
rev is omitted, the latest revision on the default branch
(see the 
-b option of #rcsrcs ) is retrieved. If
rev is $, co determines the revision number
from keyword values in the working file. Otherwise, a revision is
composed of one or more numeric or symbolic fields separated by
periods. If 
rev begins with a period, then the default
branch (normally the trunk) is prepended to it. If 
rev is
a branch number followed by a period, then the latest revision on
that branch is used. The numeric equivalent of a symbolic field
is specified with the 
-n option of the commands
See 
#ciOptnciOptn  and See #rcsOptnrcsOptn .



Lock revision 



-lrev


same as 
-r, except that it also locks the retrieved
revision for the caller.



Unlock revision 



-lrev


same as 
-r, except that it unlocks the retrieved revision
if it was locked by the caller.  If 
rev is omitted,
-u retrieves the revision locked by the caller, if there
is one; otherwise, it retrieves the latest revision on the
default branch.



Force overwriting working file 




-frev


forces the overwriting of the working file;
useful in connection with 
-q.
See 
#coFileModescoFileModes 



Keyword strings 








-kkv


Generate keyword strings using the default form, e.g.
$Revision : 5.12 $ for the
Revision keyword. A locker's name is inserted in the value
of the 
Header, Id, and Locker keyword
strings only as a file is being locked, i.e. by 
ci -l and
co -l. This is the default.
-kkvl

Like -kkv, except that a locker's name is always inserted
if the given revision is currently locked.
-kk

Generate only keyword names in keyword strings; omit their
values. See 
#coKeywordcoKeyword  below. For example, for
the 
Revision keyword, generate the string
$Revsion$ instead of $Revision: 5.12
$
. This option is useful to ignore differences due to
keyword substitution when comparing different revisions of a
file. Log messages are inserted after 
$Log$ keywords
even if 
-kk is specified, since this tends to be more
useful when merging changes.
-ko

Generate the old keyword string,
present in the working file just before it was checked in.
For example, for the 
Revision
keyword, generate the string
$Revision: 1.1 $
instead of 
$Revision: 5.12 $
if that is how the string appeared when the file was checked in.
This can be useful for file formats
that cannot tolerate any changes to substrings
that happen to take the form of keyword strings.
-kb

Generate a binary image of the old keyword string. This acts like
-ko, except it performs all working file input and output
in binary mode. This makes little difference on Posix and Unix
hosts, but on DOS-like hosts one should use 
rcs -i -kb to
initialize an RCS file intended to be used for binary files.
Also, on all hosts, 
#rcsmergercsmerge  normally refuses to merge
files when 
-kb is in effect.
-kv

Generate only keyword values for keyword strings. For example,
for the 
Revision keyword, generate the string 5.12
instead of 
$Revision: 5.12 $
This can help generate files in programming languages where it
is hard to strip keyword delimiters like
$Revision: $ from a string.
However, further keyword substitution cannot be performed once
the keyword names are removed, so this option should be used
with care. Because of this danger of losing keywords, this
option cannot be combined with 
-l, and the owner write
permission of the working file is turned off; to edit
the file later, check it out again without 
-kv.



Print on standard output 




-prev


prints the retrieved revision on the standard output rather than
storing it in the working file. This option is useful when
co is part of a pipe.



Quiet mode 



-qrev


quiet mode; diagnostics are not printed.



Interactive Mode 



-Irev


interactive mode; the user is prompted and questioned even if the
standard input is not a terminal.



Checkout by date/time 





-ddate


retrieves the latest revision on the selected branch whose checkin date/time is
less than or equal to 
date.
The date and time can be given in free format.
The time zone 
LT stands for local time;
other common time zone names are understood.
For example, the following
dates are equivalent
if local time is January 11, 1990, 8pm Pacific Standard Time,
eight hours west of Coordinated Universal Time (UTC):

8:00 pm lt
4:00 AM, Jan. 12, 1990             default is UTC
1990-01-12 04:00:00+00             ISO 8601 (UTC)
1990-01-11 20:00:00-08             ISO 8601 (local time)
1990/01/12 04:00:00                traditional RCS format
Thu Jan 11 20:00:00 1990 LT        output of ctime(3) + LT
Thu Jan 11 20:00:00 PST 1990       output of date(1)
Fri Jan 12 04:00:00 GMT 1990
Thu, 11 Jan 1990 20:00:00 -0800    Internet RFC 822
12-January-1990, 04:00 WET
 
 

Most fields in the date and time can be defaulted. The default
time zone is normally UTC, but this can be overridden by the
-z option. The other defaults are determined in the order
year, month, day, hour, minute, and second (most to least
significant).  At least one of these fields must be provided.
For omitted fields that are of higher significance than the
highest provided field, the time zone's current values are
assumed. For all other omitted fields, the lowest possible values
are assumed. For example, without 
-z, the date 20,
10:30 defaults to 10:30:00 UTC of the 20th of the UTC time
zone's current month and year. The date/time must be quoted if it
contains spaces.



Modification time 



-Mrev


Set the modification time on the new working file
to be the date of the retrieved revision.
Use this option with care; it can confuse
make.



State 



-sstate


retrieves the latest revision on the selected branch whose state
is set to 
state.



Preserve Modification time 




-T


Preserve the modification time on the RCS file even if the RCS
file changes because a lock is added or removed. This option can
suppress extensive recompilation caused by a 
make
dependency of some other copy of the working file on the RCS
file. Use this option with care; it can suppress recompilation
even when it is needed, i.e. when the change of lock would mean a
change to keyword strings in the other working file.



Checked in by user 



-wlogin


retrieves the latest revision on the selected branch which was
checked in by the user with login name 
login. If the
argument 
login is omitted, the caller's login is assumed.



Joining revisions 



-jjoinlist


generates a new revision which is the join of the revisions on
joinlist. This option is largely obsoleted by rcsmerge
(
#rcsmergercsmerge ) but is retained for backwards compatibility.
The joinlist is a comma-separated list of pairs of the
form 
rev2 : rev3, where rev2 and rev3 are
(symbolic or numeric) revision numbers. For the initial such
pair, 
rev1 denotes the revision selected by the above
options 
-f, ···, -w. For all other pairs,
rev1 denotes the revision generated by the previous pair.
(Thus, the output of one join becomes the input to the next.)
For each pair, co joins revisions rev1 and
rev3 with respect to rev2. This means that all
changes that transform 
rev2 into rev1 are applied
to a copy of 
rev3. This is particularly useful if
rev1 and rev3 are the ends of two branches that
have 
rev2 as a common ancestor.  If
rev1 < rev2 < rev3 on the same branch,
joining generates a new revision which is like 
rev3,
but with all changes that lead from 
rev1 to rev2
undone. If changes from 
rev2 to rev1 overlap
with changes from 
rev2 to rev3, co reports
overlaps as described in 
merge.
For the initial pair, rev2 can be omitted.  The default is
the common ancestor. If any of the arguments indicate branches,
the latest revisions on those branches are assumed. The options
-l and -u lock or unlock rev1.



Version, Emulate RCS Version 





-V

Print RCS's version number.
-Vn

Emulate RCS version n, where n can be 3,
4, or 5. This can be useful when interchanging RCS
files with others who are running older versions of RCS. To see
which version of RCS your correspondents are running, have them
invoke 
rcs -V; this works with newer versions of RCS. If
it doesn't work, have them invoke 
rlog ( #rlogrlog ) on an
RCS file; if none of the first few lines of output contain the
string 
branch: it is version 3; if the dates' years have
just two digits, it is version 4; otherwise, it is version 5. An
RCS file generated while emulating version 3 loses its default
branch. An RCS revision generated while emulating version 4 or
earlier has a time stamp that is off by up to 13 hours. A
revision extracted while emulating version 4 or earlier contains
abbreviated dates of the form 
yy/mm/dd and can also
contain different white space and line prefixes in the
substitution for $Log$.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files.
See 
#ciOptxciOptx  for details.



Time Zoone 



-zzoone


See 
#ciOptzciOptz  for details.



Keyword Substitution 



Strings of the form 
$keyword$ and
$keyword : ···$ embedded in
the text are replaced with strings of the form
$keyword:value$ where
keyword and value are pairs listed below.
Keywords can be embedded in literal strings or comments to
identify a revision.
Initially, the user enters strings of the form
$keyword$.
On checkout, 
co replaces these strings with strings
of the form 
$keyword:value$.
If a revision containing strings of the latter form is checked
back in, the value fields will be replaced during the next
checkout. Thus, the keyword values are automatically updated on
checkout. This automatic substitution can be modified by the
-k options.
Keywords and their corresponding values:

$Author$


The login name of the user who checked in the revision.
$Date$


The date and time the revision was checked in.
With 
-zzone a numeric time zone offset is appended;
otherwise, the date is UTC.
$Header$


A standard header containing the full pathname of the RCS file, the
revision number, the date and time, the author, the state,
and the locker (if locked). With 
-zzone
a numeric time zone offset is appended to the date;
otherwise, the date is RCS.
$Id$


Same as 
$Header$,
except that the RCS filename is without a path.
$Locker$


The login name of the user who locked the revision
(empty if not locked).
$Log$


The log message supplied during checkin, preceded by a header
containing the RCS filename, the revision number, the author, and
the date and time. With 
-zzone a numeric time zone
offset is appended; otherwise, the date is UTC. Existing log
messages are 
not replaced. Instead, the new log message is
inserted after 
$Log: ··· $. This
is useful for accumulating a complete change log in a source
file.
Each  inserted  line is prefixed by the string that prefixes the
$Log$ line.  For example, if the
$Log$ line is
"// $Log: tan.cc $",
RCS prefixes each line of the log with "// ".
This  is useful  for  languages  with  comments  that  go  to the
end of the line.  The convention for other languages is to use a
"  *  "  prefix inside a multiline comment.  For example,
the initial log comment  of  a  C  program conventionally is of
the following form:

/*
 * $Log$
 */

For  backwards compatibility with older versions of RCS, if the
log prefix is 
/* or  (* surrounded  by optional
white space, inserted log lines contain a space instead of
/ or (; however,  this  usage  is obsolescent and
should not be relied on.
$Name$


The symbolic name used to check out the revision, if any. For
example, 
"co -rJoe" generates
"$Name: Joe $".
Plain 
co generates just "$Name:  $"
$RCSFile$


The name of the RCS file without a path.
$Revsion$


The revision number assigned to the revision.
$Source$


The full pathname of the RCS file.
$State$


The state assigned to the revision with the
-s option of rcs or ci.


The following characters in keyword values are represented by escape sequences
to keep keyword strings well-formed.

char    escape sequence
tab            \t
newline        \n
space          \040
$              \044
\              \\


File Modes 


The working file inherits the read and execute permissions from
the RCS file.  In addition, the owner  write  permis- sion  is
turned  on,  unless  
-kv  is  set or the file is checked
out unlocked and locking is  set  to  strict (See 
#rcsrcs ).
If a file with the name of the working file exists already and
has write permission, 
co aborts the  checkout,  asking
beforehand  if  possible.  If the existing working file is not
writable or 
-f is given, the working file  is  deleted
without asking.

Files 


co accesses files much as ci does, except that it
does not need to read the working file unless a revision number
of 
$ is specified.

Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
See 
#ciEnvciEnv  for details.



Diagnostics 

The RCS pathname, the working pathname, and  the  revision
number  retrieved  are  written  to the diagnostic output.
The exit status is zero if and only if all operations were
successful.

Limits 

Links to the RCS and working files are not preserved.

rcs -- change RCS file attributes 




#rcsIntroIntroduction to rcs. 
#rcsOptionscommand line options of rcs. 
#rcsCompatibilityCompatibility between RCS Versions. 
#rcsFilesFiles. 
#rcsEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsDiagDiagnostic output of rcs. 
#rcsBugsBugs. 


Description 

RCS  creates new RCS files or changes attributes of existing ones.
An RCS  file  contains  multiple  revisions  of
text,  an access list, a change log, descriptive text, and
some control attributes.  For rcs to  work,  the  caller's
login  name  must  be  on  the  access list, except if the
access list is empty, the caller is the owner of the  file
or the superuser, or the 
-i option is present.
Pathnames  matching  an  RCS  suffix denote RCS files; all
others  denote  working  files.   Names  are   paired   as
explained  in  See 
#ciIntrociIntro .   Revision  numbers  use  the syntax
described in See 
#ciIntrociIntro .

Command line options of rcs 

Overview off all options which can be given to rcs
Synopsis: rcs [options] file ···

#rcsOpti-i Initialize. 
#rcsOpta-a Login names. 
#rcsOptAu-A Append access list. 
#rcsOpte-e Erase login names. 
#rcsOptb-b Set default branch. 
#rcsOptc-c Set comment leader. 
#rcsOptk-k Keyword substitution. 
#rcsOptl-l Lock revision. 
#rcsOptu-u unlock revision. 
#rcsOptLu-L Set strict locking. 
#rcsOptUu-U set non-strict locking. 
#rcsOptm-m Replace message. 
#rcsOptMu-M Do not send mail. 
#rcsOptn-n Associate symbolic name(tag). 
#rcsOptNu-N Override symbolic name. 
#rcsOpto-o Delete revisions. 
#rcsOptq-q Quiet mode. 
#rcsOptIu-I Interactive mode. 
#rcsOpts-s Set state. 
#rcsOptt-t Discription. 
#rcsOptTu-T Modification time. 
#rcsOptV-V Version; Emulation of RCS Version. 
#rcsOptx-x Suffixes. 
#rcsOptz-z Time zone. 


Initialize RCS File 



-i


Create and initialize a new RCS file,  but  do  not
deposit  any revision.  If the RCS file has no path
prefix, try to place it first into the subdirectory
./RCS, and then into the current directory.  If the
RCS file already exists, print an error message.



Append Login names 




-alogins


Append the login  names  appearing  in  the  comma-separated
list 
logins to the access list of the RCS
file.



Append Access list 



-Aoldfile


Append the access list of  
oldfile to  the  access
list of the RCS file.



Erase Login names 



-elogins


Erase  the  login  names  appearing  in  the comma-
separated list 
logins from the access list  of  the
RCS  file.   If 
logins is omitted, erase the entire
access list.



Default branch 




-brev


Set the default branch to 
rev.  If rev is  omitted,
the  default  branch  is reset to the (dynamically)
highest branch on the trunk.



Coment leader 



-cstring


Set the comment leader to 
string.  An  initial
ci, or an rcs -i without -c,
guesses the comment leader from the suffix of the
working filename.
This option is obsolescent, since RCS normally uses
the  preceding  
$Log$ line's prefix
when inserting log lines during checkout
(See 
#coIntrocoIntro ).
However, older  versions  of  RCS  use  the  comment  leader
instead of the 
$Log$ line's prefix,
so if you  plan to  access a file with both old and
new versions of RCS, make sure its comment leader
matches its 
$Log$ line prefix.



Keyword substitution 



-ksubst


Set the default keyword substitution to 
subst.  The
effect of  keyword  substitution  is  described  in
#coKeywordcoKeyword . Giving  an explicit -k option to co,
rcsdiff, and rcsmerge overrides this  default.
Beware 
rcs -kv,  because  -kv  is incompatible with
co -l. Use rcs -kkv to restore the normal default  keyword
substitution.



Lock revision 



-lrev


Lock  the revision with number 
rev.  If a branch is
given, lock the latest revision on that branch.  If
rev is  omitted,  lock  the latest revision on the
default  branch.   Locking   prevents   overlapping
changes.   If  someone else already holds the lock,
the lock is broken as with 
rcs -u (see below).



Unlock revisions 



-urev


Unlock the revision with number 
rev. If  a  branch is
given,  unlock  the  latest  revision  on  that branch.  If
rev is omitted, remove the latest  lock held by the
caller.  Normally, only the locker of a revision can unlock it.
Somebody else unlocking  a revision  breaks the lock. This causes
a mail message to be sent to the original locker. The  message
contains  a  commentary  solicited  from  the breaker.  The
commentary is terminated  by  end-of-file or by a line containing
. by itself.



Strict Locking 



-L


Set  locking  to 
strict.  Strict locking means that
the owner of an RCS file is not exempt from locking
for  checkin.  This option should be used for files
that are shared.



Locking non-strict 



-U


Set  locking  to  non-strict.   Non-strict  locking
means  that  the  owner  of  a file need not lock a
revision for checkin.  This option  should  
not be
used  for  files  that are shared.  Whether default
locking is strict  is  determined  by  your  system
administrator, but it is normally strict.



Replace log message 




-mrev:msg


Replace revision 
rev's log message with msg.



Do not send Mail 




-M


Do  not  send  mail  when  breaking somebody else's
lock.  This option is not meant for casual use;  it
is  meant  for  programs  that  warn users by other
means, and invoke 
rcs -u only as a low-level
lock-breaking operation.



Symbolic name 





-nname[:[rev]]


Associate the symbolic name 
name with the branch or
revision 
rev.  Delete the symbolic name if  both:
and 
rev are omitted; otherwise, print an error message
if 
name is  already  associated  with  another
number.   If 
rev is symbolic, it is expanded before
association.  A 
rev consisting of a  branch  number
followed by a . stands for the current latest revision
in the branch.  A : with an empty  
rev stands
for  the  current  latest  revision  on the default
branch,   normally   the   trunk.    For   example,

rcs -n
name: RCS/*

associates 
name with the current
latest revision of all the named  RCS  files;  this
contrasts  with

rcs -n
name:$ RCS/*

which associates
name with the revision numbers extracted from  keyword
strings in the corresponding working files.



Override Symbolic name 






-Nname[:[rev]]


Act  like  
-n, except override any previous assignment of
name.



Delete revisions 



-orange


deletes ("outdates") the revisions given by  
range.
A  range  consisting  of  a  single revision number
means that  revision.   A  range  consisting  of  a
branch  number  means  the  latest revision on that
branch.  A range of the form 
rev1:rev2 means
revisions 
rev1 to rev2 on the same branch,
:rev means from the beginning of the branch
containing 
rev up to  and including rev,
and 
rev: means from revision rev to the
end of the branch containing 
rev . None of  the
outdated  revisions  can  have branches or locks.



Quiet mode 



-q


Run quietly; do not print diagnostics.



Interactive 



-I


Run interactively, even if the  standard  input  is
not a terminal.



States 



-sstate:[rev]


Set  the  state  attribute  of  the revision 
rev to
state.  If rev is a branch number, assume the  latest
revision  on  that branch.  If 
rev is omitted,
assume the latest revision on the  default  branch.
Any  identifier  is acceptable for 
state .  A useful
set of states is Exp (for experimental), Stab  (for
stable), and Rel (for released).  By default, 
#ciOptsciOpts 
sets the state of a revision to Exp.



Descriptive Text 



-tfile


Write descriptive text from  the  contents  of  the
named 
file into the RCS file, deleting the existing
text.  The 
file pathname cannot begin with  -.
If 
file is  omitted,  obtain  the  text from standard
input, terminated by end-of-file or by a line  containing.
by itself.  Prompt for the text if interaction is possible;
see 
-I #rcsOptIurcsOptIu .  With  -i,  descriptive
text is obtained even if 
-t is not given.
-t-string

Write descriptive text from the string into the RCS
file, deleting the existing text.



Modification Time 



-T


Preserve the modification  time  on  the  RCS  file
unless a revision is removed.  This option can sup-
press extensive recompilation caused by  a  
make
dependency  of some copy of the working file on the
RCS file.  Use this option with care; it  can  suppress
recompilation  even  when it is needed, i.e.
when a change to the RCS file would mean  a  change
to keyword strings in the working file.



Version 




-V


Print RCS's version number.
-Vn

Emulate RCS version n.  See #coOptVcoOptV  for details.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files. See #ciOptxciOptx .



Time Zone 



-zzone


Use 
zone as the default time zone.  This option has
no  effect;  it  is  present for compatibility with
other RCS commands.



Compatibility 


The 
-brev option generates an  RCS  file  that  cannot  be
parsed by RCS version 3 or earlier.
The  -ksubst options  (except  -kkv) generate an RCS file
that cannot be parsed by RCS version 4 or earlier.
Use rcs -Vn to make an RCS file acceptable to RCS  version
n  by discarding information that would confuse version n.
RCS version 5.5  and  earlier  does  not  support  the  -x
option, and requires a 
,v suffix on an RCS pathname.

Files 


rcs accesses files much as ci does, except that it uses
the effective user for all accesses, it does not write the
working  file  or its directory, and it does not even read

Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
See 
#ciEnvciEnv  for details.



Diagnostics 

The RCS pathname and the revisions outdated are written to
the  diagnostic  output.   The  exit status is zero if and
only if all operations were successful.

Bugs 

A catastrophe (e.g. a system crash) can cause RCS to leave
behind  a  semaphore file that causes later invocations of
RCS to claim that the RCS file is in use.   To  fix  this,
remove  the semaphore file.  A semaphore file's name typically
begins with 
, or ends with _.
The separator for revision ranges in the -o option used to
be  
-  instead of :, but this leads to confusion when
symbolic names contain 
-.  For backwards compatibility
rcs -o still  supports  the  old  - separator, but it warns about
this obsolete use.
Symbolic names need not refer  to  existing  revisions  or
branches.  For example, the 
-o option does not remove symbolic
names for the outdated revisions; you must use 
-n to
remove the names.

ident -- identify RCS keywords 





#identIntroIntroduction to rcs. 
#identOptionscommand line options of rcs. 
#identKeywordsKeywords. 


Description 

Ident   searches   for   all   instances  of  the  pattern
$keyword: text $ in the named
files or, if  no  files  are named, the standard input.
These  patterns are normally inserted automatically by the
RCS command 
co ( #coKeywordcoKeyword ), but can also
be inserted manually. The option
-q(See #identOptqidentOptq )  suppresses  the
warning given if there are no patterns in a file.
The option 
-V(See #identOptVidentOptV ) prints ident's  version
number.
ident  works  on  text  files  as well as object files and
dumps.  For example, if the C program in f.c contains:

#include <stdio.h>
static char const rcsid[] =
    "$Id: f.c,v 5.4 1993/11/09  17:40:15  eggert  Exp $";
int main() { return printf("%s\n", rcsid) == EOF; }

and f.c is compiled into f.o, then the command

ident  f.c  f.o

will output

f.c:
    $Id: f.c,v 5.4 1993/11/09 17:40:15 eggert Exp $
f.o:
    $Id: f.c,v 5.4 1993/11/09 17:40:15 eggert Exp $

If a C program defines a string like rcsid above but  does
not  use  it,  
lint  may complain, and some C compilers
will optimize away the string.  The most reliable solution
is  to  have the program use the rcsid string, as shown in
the example above.
ident finds all instances of the $keyword: text $
pattern, even  if 
keyword is not actually an RCS-supported keyword.
This gives you information about nonstandard keywords like
$XConsortium$.

Command line options of ident 

Overview off all options which can be given to rcs
Synopsis: ident [options] [ file ··· ]

#identOptq-q Quiet mode. 
#identOptV-V Version 


Quiet mode 



-q


Suppress warning given if there are no patterns in a file.



Version 



-V


Print ident's version number.



Keywords 


The maintained list of keywords of 
co you'll find
in 
#coKeywordcoKeyword .
All times are given in Coordinated Universal  Time
(UTC,  sometimes  called GMT) by default, but if the files
were checked out with 
co's -zzone (See #coOptzcoOptz )
option, times are  given with a numeric time zone indication appended.

rcsclean -- clean up working files 





#rcscleanIntroIntroduction to rcsclean. 
#rcscleanOptionscommand line options of rcsclean. 
#rcscleanExamplesExamples in using rcsclean. 
#rcscleanFilesFiles. 
#rcscleanEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcscleanDiagDiagnostic output of rcsclean. 
#rcscleanBugsBugs. 


Description 

rcsclean  removes  files  that  are  not  being worked on.
rcsclean -u ( #rcscleanOpturcscleanOptu ) also unlocks and removes
files that are  being worked on but have not changed.
For  each  file given, rcsclean compares the working file
and a revision in the corresponding RCS file.  If it finds
a  difference,  it  does  nothing.   Otherwise,  it  first
unlocks the revision if the 
-u (See #rcscleanOpturcscleanOptu 
 option is given,  and  then
removes  the  working  file  unless  the  working  file is
writable and the revision is locked.  It logs its  actions
by  outputting the corresponding 
rcs -u (See #rcsOpturcsOptu )
and 
rm -f commands on the standard output.
Files are paired as explained in #ciFilesciFiles .
If  no  
file is
given,  all  working  files  in  the current directory are
cleaned.  Pathnames matching  an  RCS  suffix  denote  RCS
files; all others denote working files.
The  number  of  the revision to which the working file is
compared may be attached to any of the options 
-n,
-q, -r, or -u.
If no revision number is specified, then if the 
-u
option is given and the caller has  one  revision  locked,
rcsclean  uses  that revision; otherwise rcsclean uses the
latest revision on the default branch, normally the  root.
rcsclean is  useful  for clean targets in makefiles.
See 
#rcsdiffrcsdiff , which prints  out  the  differences,  and
ci ( #ciIntrociIntro ),  which normally reverts to the
previous revision if a file was not changed.

Command line options of rcsclean 

Overview off all options which can be given to rcsclean
Synopsis: rcsclean [options] [ file ··· ]

#rcscleanOptk-k Keyword substitution. 
#rcscleanOptn-n Do not unlock or remove. 
#rcscleanOptq-q Quiet mode. 
#rcscleanOptr-r Revision for comparison. 
#rcscleanOptT-T Modification time. 
#rcscleanOptu-u unlock revisions. 
#rcscleanOptV-V Version; Emulation RCS Version. 
#rcscleanOptx-x Suffixes. 
#rcscleanOptz-z Time zone. 


Keyword substitution 



-ksubst


Use 
subst style keyword substitution when  retrieving
the  revision  for  comparison.  See 
#coKeywordcoKeyword 
for details.



No removing 




-nrev


Do not actually remove  any  files  or  unlock  any
revisions.   Using  this  option will tell you what
rcsclean would do without actually doing it.



Quiet mode 



-qrev


Do not log the actions taken on standard output.



Revision for comparison 




-rrev


This option has no effect other than specifying the
revision for comparison.



Modification time 




-T


Preserve the modification time on the RCS file even
if the RCS file changes because a lock is  removed.
This  option  can  suppress extensive recompilation
caused by a 
make dependency of some  other  copy
of  the  working  file  on  the RCS file.  Use this
option with care;  it  can  suppress  recompilation
even  when it is needed, i.e. when the lock removal
would mean a change to keyword strings in the other
working file.



Unlock revision 



-urev


Unlock  the revision if it is locked and no difference is found.



Version and Emulation 




-V


Print RCS's version number.
-Vn

Emulate RCS version n.  See #coOptVcoOptV  for details.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files.  See  #ciOptxciOptx 
for details.



Time zone 



-zzone


-zzone Use zone as the time zone for keyword substitution;
see 
#coOptzcoOptz  for details.



Examples 



rcsclean  *.c  *.h

removes all working files ending in .c or .h that were not
changed since their checkout.

rcsclean

removes  all  working  files in the current directory that
were not changed since their checkout.

Files 


rcsclean accesses files much as ci ( #ciFilesciFiles )does.

Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
See 
#ciEnvciEnv  for details.



Diagnostics 

The exit status is zero if and only if all operations were
successful.   Missing  working  files  and  RCS  files are
silently ignored.

Bugs 

At  least  one  
file must be given in older Unix versions
that do not provide the needed directory  scanning  operations.

rcsdiff -- compare RCS revisions 




#rcsdiffIntroIntroduction to rcsdiff. 
#rcsdiffOptionscommand line options of rcsdiff. 
#rcsdiffExamplesExamples in using rcsdiff. 
#rcsdiffEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsdiffDiagDiagnostic output of rcsdiff. 


Description 

rcsdiff  runs diff to compare two revisions of each RCS
file given.
Pathnames matching an RCS suffix  denote  RCS  files;  all
others   denote   working  files.   Names  are  paired  as
explained in 
#ciFilesciFiles .

Command line options of rcsdiff 

Overview off all options which can be given to rcsdiff
Synopsis: rcsdiff [options] [-rrev1] [-rrev2]  [diff options] [ file ··· ]

#rcsdiffOptk-k Keyword substitution. 
#rcsdiffOptq-q Quiet mode. 
#rcsdiffOptr-r Revision for comparison. 
#rcsdiffOptT-T Modification time. 
#rcsdiffOptV-V Version; Emulation RCS Version. 
#rcsdiffOptx-x Suffixes. 


Keyword substitution 



-ksubst


-ksubst affects keyword substitution when extracting
revisions, as described in 
#coOptkcoOptk ; for example,
-kk -r1.1 -r1.2 ignores differences in keyword values
when comparing revisions  
1.1  and  1.2.
To avoid excess output from locker name substitution,
-kkvl is assumed if

.&larrow.at  most  one revision  option  is given,


.&larrow.no -k option is given,

.&larrow.-kkv is the default  keyword  substitution,  and

.&larrow.the working file's mode would be produced by co -l.






Quiet mode 



-qrev


The option -q suppresses diagnostic output.



Revision for comparison 




-rrev1 -rrev2


Zero, one, or two  revisions  may  be  specified  with  
-r.
If both 
rev1 and rev2 are omitted,  rcsdiff  compares  the
latest  revision  on  the  default  branch (by default the
trunk) with the  contents  of  the  corresponding  working
file.   This  is  useful  for determining what you changed
since the last checkin.
If rev1 is given, but rev2 is  omitted,  rcsdiff  compares
revision  
rev1 of  the  RCS file with the contents of the
corresponding working file.
If both rev1 and rev2 are given,  rcsdiff  compares
revisions 
rev1 and rev2 of the RCS file.
Both  rev1 and  rev2 may be given numerically or symbolically.



Modification time 




-T


For details See 
#coOptTcoOptT .



Version and Emulation 




-V


Print RCS's version number.
-Vn

Emulate RCS version n.  See #coOptVcoOptV  for details.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files.  See  #ciOptxciOptx 
for details.



Examples 



rcsdiff  *.c  *.h

removes all working files ending in .c or .h that were not
changed since their checkout.

rcsdiff

removes  all  working  files in the current directory that
were not changed since their checkout.

Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
See 
#ciEnvciEnv  for details.



Diagnostics 

Exit status is 0 for no differences during any comparison,
1 for some differences, 2 for trouble.

rcsmerge -- merge RCS versions 




#rcsmergeIntroIntroduction to rcs. 
#rcsmergeOptionscommand line options of rcs. 
#rcsmergeExamplesExamples of rcsmerge. 
#rcsmergeEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rcsmergeDiagDiagnostic output of rcs. 


Description 

rcsmerge incorporates the changes between two revisions of
an RCS file into the corresponding working file.
Pathnames matching an RCS suffix  denote  RCS  files;  all
others   denote   working  files.   Names  are  paired  as
explained in 
#ciFilesciFiles .
At least one revision must be specified with  one  of  the
options  described  below,  usually 
-r.
At most two revisions may be specified.  If only one
revision  is  specified,  the latest revision on the
default branch (normally the highest branch on the
trunk) is assumed for the second revision.
Revisions may be specified numerically or symbolically.
rcsmerge prints a  warning  if  there  are  overlaps,  and
delimits the overlapping regions as explained in 
#mergemerge .
The command is useful for  incorporating  changes  into  a
checked-out revision.

Command line options of rcsmerge 

Overview off all options which can be given to rcsmerge
Synopsis: rcsmerge [options] file ···

#rcsmergeOptA-A Output conflicts the -A style. 
#rcsmergeOptE-E specify Conflict style 
#rcsmergeOptk-k Keyword substitution. 
#rcsmergeOptp-p send to stdout. 
#rcsmergeOptT-T Modification time. 
#rcsmergeOptV-V Version; Emulation of RCS Version. 
#rcsmergeOptx-x Suffixes. 
#rcsmergeOptz-z Time zone. 


Output conflicts 




-A


Output conflicts using the 
-A style of diff3, if
supported by 
diff3.  This merges all changes  leading
from  
file2 to file3 into file1, and generates
the most verbose output.



Less information 




-E -e


These options specify conflict styles that generate
less   information   than  
-A.   See  diff3  for
details.  The default is  
-E. With  -e,  rcsmerge
does not warn about conflicts.



Keyword substitution 



-ksubst


Use  
subst style  keyword substitution.
See 
#coKeywordcoKeyword  for details.
For example, 
-kk -r1.1 -r1.2  ignores
differences  in  keyword  values  when  merging the
changes from 
1.1 to 1.2.  It normally
does not make sense  to  merge binary files as if
they were text, so 
rcsmerge refuses to merge
files if 
-kb expansion is used.



Send to standard out 




-p[rev]


Send the result to standard output instead of over-
writing the working file.



Modification Time 



-T


This option has no effect; it is present  for  compatibility
with other RCS commands.



Version 




-V


Print RCS's version number.
-Vn

Emulate RCS version n.  See #coOptVcoOptV  for details.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files. See #ciOptxciOptx .



Time Zone 



-zzone


Use 
zone as the time zone for keyword substitution.
See 
#coOptzcoOptz  for details.



Examples 


Suppose  you  have  released  revision 
2.8 of f.c.  Assume
furthermore that after you complete an unreleased revision
3.4, you receive updates to release 2.8 from someone else.
To combine the updates to 
2.8 and your changes between 2.8
and 
3.4, put the updates to 2.8 into file f.c and execute

rcsmerge  -p  -r2.8  -r3.4  f.c  >f.merged.c

Then  examine  f.merged.c.   Alternatively, if you want to
save the updates to 
2.8 in the RCS file, check them in  as
revision 
2.8.1.1 and execute co -j:

ci  -r2.8.1.1  f.c
co  -r3.4  -j2.8:2.8.1.1  f.c

As  another  example,  the  following  command  undoes the
changes between revision 
2.4 and  2.8  in  your  currently
checked out revision in 
f.c.

rcsmerge  -r2.8  -r2.4  f.c

Note  the  order  of  the  arguments, and that f.c will be
overwritten.

Environment 


RCSINIT

options prepended to the argument list, separated by spaces.
See 
#ciEnvciEnv  for details.



Diagnostics 

Exit  status  is 0 for no overlaps, 1 for some overlaps, 2
for trouble.

rlog -- print log messages 





#rlogIntroIntroduction to rlog. 
#rlogOptionscommand line options of rlog. 
#rlogExamplesExamples. 
#rlogEnvThe Environment which can change the behaviour of much of the RCS commands. 
#rlogDiagDiagnostic output of rlog. 
#rlogBugsBugs. 


Description 

rlog prints information about RCS files.
Pathnames matching an RCS suffix  denote  RCS  files;  all
others   denote   working  files.   Names  are  paired  as
explained in 
#ciFilesciFiles .
rlog prints the following information for each  RCS  file:
RCS  pathname, working pathname, head (i.e., the number of
the latest revision on the trunk), default branch,  access
list, locks, symbolic names, suffix, total number of revisions,
number of  revisions  selected  for  printing,  and
descriptive  text.   This  is  followed by entries for the
selected revisions in reverse chronological order for each
branch.   For  each revision, rlog prints revision number,
author, date/time, state, number  of  lines  added/deleted
(with  respect  to  the  previous revision), locker of the
revision (if any), and log message.  All  times  are  displayed
in  Coordinated  Universal  Time (UTC) by default;
this can be overridden with  
-z.   Without  options,
rlog prints  complete  information.
The options below restrict this output.

Command line options of rlog 


Overview off all options which can be given to rlog
Synopsis: rlog [options] file ···

#rlogOptLu-L Ignore RCS files. 
#rlogOptRu-R Only names of RCS files. 
#rlogOpth-h Only path names. 
#rlogOptt-t Path and discriptive text. 
#rlogOptN-N Do not print symbolic names.. 
#rlogOptb-b Information about revisions on default branch. 
#rlogOptd-d Info about revisions with ci-date. 
#rlogOptl-l Print locked revisions only. 
#rlogOptr-r Informations about specified revisions. 
#rlogOpts-s Informations about revisions with state. 
#rlogOptw-w Informations about revisions with user. 
#rlogOptTu-T no effect. 
#rlogOptV-V Version; Emulation of RCS version. 
#rlogOptx-x Suffixes. 
#rlogOptz-z Time zone. 


Ignore RCS files without locks 




-L


Ignore RCS files that have no locks set.  This is convenient
in combination with 
-h, -l, and -R.



Only names of RCS files 



-R


Print  only  the name of the RCS file.  This is convenient
for translating a working pathname into  an  RCS
pathname.



Only pathname 



-h


Print  only  the RCS pathname, working pathname, head,
default branch, access list,  locks,  symbolic  names,
and suffix.



Descriptive text 



-t


Print the same as 
-h, plus the descriptive text.



No symbolic name 



-N


Do not print the symbolic names.



Default branch 



-b


Print  information  about the revisions on the default
branch, normally the highest branch on the trunk.



Checkin date/time 



-ddates


Print  information  about  revisions  with  a  checkin date/time
in  the  ranges  given  by  the  semicolon-separated list of
dates.  A range of the form d1<d2 or
d2>d1 selects  the  revisions  that  were
deposited between 
d1 and d2 exclusive.  A range of
the  form <
d or  d>  selects all revisions earlier
than 
d. A range of the form d< or >d selects
all revisions dated later than  
d.   If  < or
> is followed by = then the ranges are inclusive,
not exclusive.  A range of the  form  
d selects  the
single,  latest revision dated 
d or earlier.  The date/time
strings 
d, d1, and d2 are in  the free
format  explained in 
#coOptdcoOptd . Quoting is normally necessary,
especially for 
< and >. Note that the separator is
a semicolon.



Locked revisions 



-llockers


Print  information  about  locked  revisions only.  In
addition, if the comma-separated list 
lockers of login
names is given, ignore all locks other than those held
by the 
lockers.  For  example,

rlog -L -R -lwft RCS/*

prints the name of RCS files locked by the user wft.



Informations about revisions 



-rrevisions


prints information about revisions given in the commaseparated
list 
revisions of revisions and  ranges. A range
rev1:rev2 means  revisions rev1 to
rev2 on the same branch, :rev means
revisions from  the  beginning of  the branch up to and including
rev , and rev:  means revisions starting
with 
rev to the end of  the  branch containing rev.
An  argument that is a branch means all revisions on that branch.
A  range  of  branches means  all revisions on the branches in
that range.  A branch followed by a . means the  latest  revision
in that  branch. A  bare 
-r with no revisions means
the latest revision on the default  branch,  normally  the trunk.



Information about Rev. with given state 



-sstates


prints   information   about   revisions  whose  state
attributes match one of the states given in the commaseparated
list 
states.



Revisons checked in by user 



-wlogins


prints information about revisions checked in by users
with login names appearing in the comma-separated list
logins.   If  logins is  omitted, the user's login is
assumed.



Modification Time 



-T


This option has no effect; it is present for  compatibility
with other RCS commands.



Version and Emulation 




-V


Print RCS's version number.
-Vn

Emulate RCS version n when generating logs.  See
#coOptVcoOptV  for more.



Suffixes 



-xsuffixes


Use 
suffixes to characterize RCS files.  See #ciOptxciOptx  for
details.



Time zone 



Rlog  prints  the  intersection  of the revisions selected
with the options 
-d, -l, -s, and -w,
intersected with  the union of the revisions selected by
-b and -r.
-zzone

specifies the date output format, and specifies the
default time zone for 
date in the  -ddates option.
The  
zone should be empty, a numeric UTC offset, or
the special string 
LT for local time.  The  default
is  an  empty  
zone , which uses the traditional RCS
format of UTC without any time zone indication  and
with slashes separating the parts of the date; oth-
erwise, times are output in ISO  8601  format  with
time  zone  indication.  For example, if local time
is January 11, 1990,  8pm  Pacific  Standard  Time,
eight hours west of UTC, then the time is output as
follows:

option    time output
-z        1990/01/12 04:00:00       (default)
-zLT      1990-01-11 20:00:00-08
-z+05:30  1990-01-12 09:30:00+05:30




Examples 



rlog  -L  -R  RCS/*
rlog  -L  -h  RCS/*
rlog  -L  -l  RCS/*
rlog  RCS/*

The first command prints the names of all RCS files in the
subdirectory  RCS  that  have  locks.   The second command
prints the headers of those files, and  the  third  prints
the headers plus the log messages of the locked revisions.
The last command prints complete information.

Environment 


RCSINIT


options prepended to the argument  list,  separated
by spaces.  See 
#ciEnvciEnv  for details.



Diagnostics 

The exit status is zero if and only if all operations were
successful.

Bugs 


The separator for revision ranges in the 
-r option used to
be  
-  instead of :, but this leads to confusion when symbolic
names contain 
-.  For backwards  compatibility
rlog -r  still supports the old - separator, but it warns about
this obsolete use.

merge -- three-way file merge 




#mergeIntroIntroduction to merge. 
#mergeOptionscommand line options of merge. 
#mergeDiagDiagnostic output of merge. 
#mergeBugsBugs. 


Description 

merge  incorporates  all  changes  that lead from file2 to
file3 into file1.  The result ordinarily goes
into  
file1.
merge is useful for combining separate changes to an original.
Suppose 
file2 is the original, and both  file1 and
file3 are  modifications  of  file2 .  Then merge combines
both changes.
A conflict occurs if both file1 and file3 have changes  in
a  common segment of lines.  If a conflict is found, merge
normally outputs a warning and brackets the conflict  with
<<<<<<<  and  >>>>>>> lines.  A typical conflict will look
like this:

<<<<<<< file A
lines in file A
=======
lines in file B
>>>>>>> file B

If there are conflicts, the user should  edit  the  result
and delete one of the alternatives.

Command line options of merge 

Overview off all options which can be given to 
merge
Synopsis: merge [options] file1 file2 file3

#mergeOptA-A Style of diff3. 
#mergeOptE-E Conflict style. 
#mergeOptL-L Labels. 
#mergeOptp-p Send to standard output. 
#mergeOptq-q Quite mode. 
#mergeOptV-V Version. 


Output conflicts 




-A


Output conflicts using the 
-A style of diff3, if
supported by diff3.  This merges all changes  leading
from  
file2 to file3 into file1, and generates
the most verbose output.



Specify conflict styles 





-E -e


These options specify conflict styles that generate
less   information   than  
-A.   See  diff3  for
details.  The default is 
-E.  With -e,  merge  does
not warn about conflicts.



Label 


-Llabel


This  option  may  be  given up to three times, and
specifies labels to be used in place of the  corresponding
file names in conflict reports.  That is,
merge -L x -L y -L z a b c  generates  output  that
looks like it came from files 
x, y and zinstead of
from files 
a, b and c.



Standard output 



-p


Send results to standard output  instead  of  overwriting
file1.



Quiet Mode 



-q


Quiet;  do  not  warn about conflicts.



Version 



-V


Print's version number.



Diagnostics 

Exit status is 0 for no conflicts, 1 for some conflicts, 2
for trouble.

Bugs 

It normally does not make sense to merge binary  files  as
if they were text, but merge tries to do it anyway.

Format of RCS file 





#rcsfileIntroDiscription of the RCS file format. 
#rcsfileExampleExample of a revision tree. 


Description 

An RCS file's contents are described by the grammar below.
The text is free format: space, backspace,  tab,  newline,
vertical  tab,  form  feed,  and  carriage return (collectively,
white space)  have  no  significance  except  in
strings.  However, white space cannot appear within an id,
num, or sym, and an RCS file must end with a newline.
Strings are enclosed by @.  If a string contains a  @,  it
must  be doubled; otherwise, strings can contain arbitrary
binary data.
The meta syntax uses the following conventions: `|'  (bar)
separates  alternatives;  `{'  and  `}'  enclose  optional
phrases; `{' and `}*' enclose phrases that can be repeated
zero or more times; `{' and '}+' enclose phrases that must
appear at least once and can be repeated; Terminal symbols
are in boldface; nonterminal symbols are in 
italic.

rcstext    ::=  admin {delta}* desc {deltatext}*
admin      ::=  
head {num};
                { branch   {num}; }
                
access {id}*;
                
symbols {sym : num}*;
                
locks {id : num}*;  {strict  ;}
                { 
comment  {string}; }
                { 
expand   {string}; }
                { newphrase }*
delta      ::=  num
                
date num;
                
author id;
                
state {id};
                
branches {num}*;
                
next {num};
                { newphrase }*
desc       ::=  
desc string
deltatext  ::=  num
                
log string
                { newphrase }*
                
text string
num        ::=  {digit | .}+
digit      ::=  0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
id         ::=  {num} idchar {idchar | num }*
sym        ::=  {digit}* idchar {idchar | digit }*
idchar     ::=  any visible graphic character except 
special
special    ::=  $ | , | . | : | ; | @
string     ::=  @{any character, with @ doubled}*@
newphrase  ::=  id word* ;
word       ::=  id | num | string | :

Identifiers  are  case  sensitive. Keywords are in lower case
only.  The sets of keywords and identifiers can overlap. In most
environments RCS uses the ISO 8859/1 encoding: visible graphic
characters  are  codes  041-176  and 240-377,  and white space
characters are codes 010-015 and 040.
Dates, which appear after the date  keyword,  are  of  the form
Y.mm.dd.hh.mm.ss,  where Y is the year, mm
the month (01-12), 
dd the day (01-31), hh the hour
(00-23), 
mm the minute  (00-59),  and  ss the
second (00-60). 
Y contains just the last two digits of the
year for years  from 1900 through  1999,  and  all  the  digits
of years thereafter. Dates use the Gregorian calendar; times use
UTC.
The newphrase productions in the grammar are reserved
for future  extensions  to  the  format of RCS files.  No
newphrase will begin with any keyword already in use.
The delta nodes form a tree.  All nodes whose numbers consist
of a single pair (e.g., 2.3, 2.1, 1.3, etc.)  are on
the trunk, and are linked through the next field in  order
of  decreasing  numbers.  The head field in the 
admin node
points to the head of that sequence  (i.e.,  contains  the
highest  pair).   The  branch node in the admin node indicates
the default branch (or revision) for most RCS operations.
If empty, the default branch is the highest branch
on the trunk.
All delta nodes whose numbers consist of 2n fields
(
n>=2) (e.g.,  3.1.1.1,  2.1.2.2,  etc.) are linked as follows.
All nodes whose first 2
n-1 number fields are identical are
linked  through the next field in order of increasing numbers.
For each such sequence, the 
delta node whose number
is identical to the first 2
n-2 number fields of the deltas
on that sequence is called the branchpoint.  The  branches
field  of  a  node  contains  a list of the numbers of the
first nodes of all sequences for which  it  is  a  branchpoint.
This list is ordered in increasing numbers.

Example Revision tree 

The  following  diagram  shows an example of an RCS file's
organization.

                           Head
                             |
                             v                        / \
                         ---------                   /   \
   / \          / \      |       |      / \         /     \
  /   \        /   \     |  2.1  |     /   \       /       \
 /     \      /     \    |       |    /     \     /         \
/1.2.1.3\    /1.3.1.1\   |       |   /1.2.2.2\   /1.2.2.1.1.1\
---------    ---------   ---------   ---------   -------------
    ^            ^           |           ^             ^
    |            |           v           |             |
   / \           |       ---------      / \            |
  /   \          |       \  1.3  /     /   \           |
 /     \         ---------\     /     /     \-----------
/1.2.1.1\                  \   /     /1.2.2.1\
---------                   \ /      ---------
    ^                        |           ^
    |                        v           |
    |                    ---------       |
    |                    \  1.2  /       |
    ----------------------\     /---------
                           \   /
                            \ /
                             |
                             v
                         ---------
                         \  1.1  /
                          \     /
                           \   /
                            \ /


Books and related manuals 


#FeldmanGNU - Make. 
#HuntGNU - diff. 
#RochkindSCCS. 
#TichyDesign and implementation of RCS. 
#LeblangComputer-Aided Software Engineering. 
#GlasserThe Evolution of a Source Code Control System. 
#BrownThe Clear/Caster System. 
#HabermannA Software Development Control System. 
#DECCode Management System. 
#LampsonPractical Use of a Polymorphic Applicative Language. 
#Tichy1A Data Model for Programming Support Environments and its Application. 
#HeckelA Technique for Isolating Differences Between Files. 
#Tichy2The String-to-String Correction Problem with Block Moves. 


Feldman,Stuart I. 





Feldman, Stuart I.,
"Make -- A Program for Maintaining Computer Programs",
Software -- Practice & Experience,
vol. 9, no. 3, pp. 255-265, March 1979.


Hunt, James W. and McIlroy, M. D. 





Hunt, James W. and McIlroy, M. D.,
"An Algorithm for Differential File Comparison",
41, Computing Science Technical Report,
Bell Laboratories, June 1976.


Rochkind, Marc J. 



Rochkind, Marc J.
"The Source Code Control System",
IEEE Transactions on Software Engineering, vol. SE-1,
no. 4, pp. 364-370, Dec. 1975.


Tichy, Walter F. 



Tichy, Walter F.
"Design, Implementation, and Evaluation of a Revision Control System"
Proceedings of the 6th International Conference on Software Engineering,
pp. 58-67, ACM, IEEE, IPS, NBS, September 1982.


Leblang, David B. and Chase, Robert P. 





Leblang, David B. and Chase, Robert P.
"Computer-Aided Software Engineering in a Distributed
Workstation Environment",
SIGPLAN Notices, vol. 19, no. 5, pp. 104-112, May 1984.
Proceedings of the ACM SIGSOFT/SIGPLAN Software Engineering Symposium
on Practical Software Development Environments.


Glasser, Alan L. 




Glasser, Alan L.
"The Evolution of a Source Code Control System"
Software Engineering Notes, vol. 3, no. 5, pp. 122-125, Nov. 1978.
Proceedings of the Software Quality and Assurance Workshop.


Brown, H.B. 



Brown, H.B.
"The Clear/Caster System",
Nato Conference on Software Engineering, Rome 1970


Habermann, A. Nico 



Habermann, A. Nico
"A Software Development Control System",
Technical Report, Carnegie-Mellon University,
Department of Computer Science, Jan. 1979.


Code Management System 




Digital Equipment Corporation
"Code Management System",
Document No. EA-23134-82, 1982


Lampson, Butler W. and Schmidt, Eric E. 




Lampson, Butler W. and Schmidt, Eric E.
"Practical Use of a Polymorphic Applicative Language",
Proceedings of the 10th Symposium on Principles of
Programming Languages,
pp. 237-255, ACM, January 1983.


Tichy, Walter F. 






Tichy, Walter F.
"A Data Model for Programming Support Environments and its Application",
Automated Tools for Information System Design and Development, ed.
Hans-Jochen Schneider and Anthony I. Wasserman,
North-Holland Publishing Company, Amsterdam 1982.


Heckel, Paul 





Heckel, Paul
"A Technique for Isolating Differences Between Files",
Communications of the ACM, vol. 21, no. 4, pp. 264-268, April
1978.


Tichy, Walter F. 




Tichy, Walter F.
"The String-to-String Correction Problem with Block Moves",
ACM Transactions on Computer Systems, vol. 2, no. 4, pp. 309-321,
Nov. 1984.


Index 


-a

#hd_145Append Login names 
#hd_146Append Access list 
#hd_183Output conflicts 
#hd_206Output conflicts 

-b

#hd_103Default branch 
#hd_196Default branch 

-c

#hd_148Coment leader 

-d

#hd_118date 
#hd_135Checkout by date/time 
#hd_197Checkin date/time 

-e

#hd_147Erase Login names 
#hd_184Less information 
#hd_207Specify conflict styles 

-f

#hd_112force a deposit 
#hd_130Force overwriting working file 

-h

#hd_193Only pathname 

-i

#hd_115initial check in 
#hd_117interactive mode 
#hd_134Interactive Mode 
#hd_144Initialize RCS File 
#hd_159Interactive 

-j

#hd_116just check in 
#hd_140Joining revisions 

-k

#hd_113keyword values 
#hd_149Keyword substitution 
#hd_169Keyword substitution 
#hd_177Keyword substitution 
#hd_185Keyword substitution 

-kb

#hd_131Keyword strings 

-kk

#hd_131Keyword strings 

-kkv

#hd_131Keyword strings 

-kkvl

#hd_131Keyword strings 

-ko

#hd_131Keyword strings 

-kv

#hd_131Keyword strings 

-l

#hd_110lock a revision 
#hd_128Lock revision 
#hd_150Lock revision 
#hd_152Strict Locking 
#hd_191Ignore RCS files without locks 
#hd_198Locked revisions 
#hd_208Label 

-M

#hd_119modification time 
#hd_105log message 
#hd_136Modification time 
#hd_154Replace log message 
#hd_155Do not send Mail 

-n

#hd_107symbolic name 
#hd_108replace symbolic name 
#hd_143Symbolic name 
#hd_156Override Symbolic name 
#hd_170No removing 
#hd_195No symbolic name 

-o

#hd_157Delete revisions 

-p

#hd_132Print on standard output 
#hd_186Send to standard out 
#hd_209Standard output 

-q

#hd_114quiet 
#hd_133Quiet mode 
#hd_158Quiet mode 
#hd_166Quiet mode 
#hd_171Quiet mode 
#hd_178Quiet mode 
#hd_210Quiet Mode 

-r

#hd_109Check in revision 
#hd_127Check out revision 
#hd_172Revision for comparison 
#hd_179Revision for comparison 
#hd_192Only names of RCS files 
#hd_199Informations about revisions 

-s

#hd_120states 
#hd_137State 
#hd_160States 
#hd_200Information about Rev. with given state 

-t

#hd_106description 
#hd_121modification time 
#hd_138Preserve Modification time 
#hd_161Descriptive Text 
#hd_162Modification Time 
#hd_173Modification time 
#hd_180Modification time 
#hd_187Modification Time 
#hd_194Descriptive text 
#hd_202Modification Time 

-t-

#hd_106description 

-u

#hd_111unlock a revision 
#hd_129Unlock revision 
#hd_151Unlock revisions 
#hd_153Locking non-strict 
#hd_168Unlock revision 

-V

#hd_123version and emulation 
#hd_126Version, Emulate RCS Version 
#hd_163Version 
#hd_167Version 
#hd_174Version and Emulation 
#hd_181Version and Emulation 
#hd_188Version 
#hd_203Version and Emulation 
#hd_211Version 

-w

#hd_122login 
#hd_139Checked in by user 
#hd_201Revisons checked in by user 

-x

#hd_124suffixes 
#hd_141Suffixes 
#hd_164Suffixes 
#hd_175Suffixes 
#hd_182Suffixes 
#hd_189Suffixes 
#hd_204Suffixes 

-z

#hd_125time zoone 
#hd_142Time Zoone 
#hd_165Time Zone 
#hd_176Time zone 
#hd_190Time Zone 
#hd_205Time zone 

About

#hd_2About the manual 

Access

#hd_145Append Login names 

Access Liste

#hd_146Append Access list 

ACM

#hd_98Lampson, Butler W. and Schmidt, Eric E. 
#hd_100Heckel, Paul 

Block moves

#hd_101Tichy, Walter F. 

branch

#hd_103Default branch 

Bugs

#hd_81Bugs 

change RCS

#hd_43rcs -- change RCS file attributes 

check in

#hd_25ci -- check in RCS revisions 

check out

#hd_34co -- check out RCS revisions 
#hd_135Checkout by date/time 

Checked in by user

#hd_201Revisons checked in by user 

Checkin date/time

#hd_197Checkin date/time 

ci

#hd_25ci -- check in RCS revisions 

clean up

#hd_55rcsclean -- clean up working files 

Clear/Caster

#hd_95Brown, H.B. 
#hd_96Habermann, A. Nico 

co

#hd_34co -- check out RCS revisions 

Code Management System

#hd_97Code Management System 

Command line options

#hd_77Command line options of rlog 

comment leader

#hd_148Coment leader 

compare revisions

#hd_63rcsdiff -- compare RCS revisions 

comparison

#hd_172Revision for comparison 
#hd_179Revision for comparison 

Compatibility

#hd_46Compatibility 

conflict

#hd_184Less information 

conflict styles

#hd_207Specify conflict styles 

Data Model

#hd_99Tichy, Walter F. 

date

#hd_118date 
#hd_135Checkout by date/time 

DEC

#hd_97Code Management System 

Default branch

#hd_196Default branch 

default form

#hd_131Keyword strings 

Delete revision

#hd_157Delete revisions 

description

#hd_106description 

Descriptive

#hd_161Descriptive Text 

Descriptive text

#hd_194Descriptive text 

diagnostic

#hd_114quiet 

diff

#hd_183Output conflicts 
#hd_90Hunt, James W. and McIlroy, M. D. 
#hd_100Heckel, Paul 

diff3

#hd_183Output conflicts 
#hd_206Output conflicts 
#hd_207Specify conflict styles 

Differences between files

#hd_100Heckel, Paul 

Emulate

#hd_126Version, Emulate RCS Version 

emulate RCS Version

#hd_123version and emulation 

Emulation

#hd_203Version and Emulation 

Emulation of RCS

#hd_163Version 
#hd_188Version 

Emulation of RCS Version

#hd_174Version and Emulation 
#hd_181Version and Emulation 

Environment

#hd_38Environment 
#hd_48Environment 
#hd_60Environment 
#hd_67Environment 
#hd_73Environment 
#hd_79Environment 

Environments

#hd_99Tichy, Walter F. 

Erase Login names

#hd_147Erase Login names 

Examples

#hd_58Examples 
#hd_66Examples 
#hd_72Examples 
#hd_78Examples 

Feldman Stuart I.

#hd_89Feldman,Stuart I. 

file merge

#hd_82merge -- three-way file merge 

File Modes

#hd_39File Modes 

Files

#hd_40Files 
#hd_47Files 
#hd_59Files 

force a deposit

#hd_112force a deposit 

Format

#hd_87Format of RCS file 

Format of RCS files.

#hd_87Format of RCS file 

GNU-Diff

#hd_90Hunt, James W. and McIlroy, M. D. 

GNU-Make

#hd_89Feldman,Stuart I. 

Hunt, James W. and McIlroy, M. D.

#hd_90Hunt, James W. and McIlroy, M. D. 

ident

#hd_51ident -- identify RCS keywords 

identify Keywords

#hd_51ident -- identify RCS keywords 

Ignore

#hd_191Ignore RCS files without locks 

Information

#hd_75rlog -- print log messages 

Information about Revisions

#hd_199Informations about revisions 

Information Rev. given state

#hd_200Information about Rev. with given state 

initial checkin

#hd_115initial check in 

Initialize

#hd_144Initialize RCS File 

Interactiv

#hd_159Interactive 

interactive

#hd_117interactive mode 
#hd_134Interactive Mode 

interactive mode

#hd_117interactive mode 

Introduction

#hd_19Introduction to RCS commands 

join

#hd_140Joining revisions 

just checkin

#hd_116just check in 

Keyword

#hd_37Keyword Substitution 
#hd_149Keyword substitution 
#hd_169Keyword substitution 
#hd_177Keyword substitution 
#hd_185Keyword substitution 

Keyword Author

#hd_37Keyword Substitution 

Keyword Date

#hd_37Keyword Substitution 

Keyword Header

#hd_37Keyword Substitution 

Keyword Id

#hd_37Keyword Substitution 

Keyword Locker

#hd_37Keyword Substitution 

Keyword Log

#hd_37Keyword Substitution 

Keyword Name

#hd_37Keyword Substitution 

Keyword RCSFile

#hd_37Keyword Substitution 

Keyword Revision

#hd_37Keyword Substitution 

Keyword Source

#hd_37Keyword Substitution 

Keyword State

#hd_37Keyword Substitution 

keyword values

#hd_113keyword values 

Keywords

#hd_51ident -- identify RCS keywords 
#hd_54Keywords 

lock

#hd_128Lock revision 
#hd_129Unlock revision 

lock a revision

#hd_110lock a revision 

Lock breaking

#hd_155Do not send Mail 

Lock revsion

#hd_150Lock revision 

Locked revisions

#hd_198Locked revisions 

log message

#hd_105log message 
#hd_154Replace log message 

log messages

#hd_75rlog -- print log messages 

login

#hd_122login 
#hd_139Checked in by user 

Login names

#hd_145Append Login names 

Mail

#hd_155Do not send Mail 

Make

#hd_89Feldman,Stuart I. 

merge

#hd_82merge -- three-way file merge 

merge revisions

#hd_69rcsmerge -- merge RCS versions 

Modification

#hd_136Modification time 
#hd_138Preserve Modification time 
#hd_173Modification time 
#hd_180Modification time 

modification time

#hd_119modification time 
#hd_121modification time 
#hd_162Modification Time 
#hd_187Modification Time 
#hd_202Modification Time 

name

#hd_143Symbolic name 
#hd_156Override Symbolic name 

Names

#hd_192Only names of RCS files 

no lock

#hd_191Ignore RCS files without locks 

no Symbolic name

#hd_195No symbolic name 

non-Strict Locking

#hd_153Locking non-strict 

output

#hd_132Print on standard output 
#hd_186Send to standard out 

Output conflicts

#hd_206Output conflicts 

override symbolic name

#hd_108replace symbolic name 
#hd_156Override Symbolic name 

overwriting

#hd_130Force overwriting working file 

pathname

#hd_193Only pathname 

Polymorhpic Applicative Language

#hd_98Lampson, Butler W. and Schmidt, Eric E. 

preserve

#hd_138Preserve Modification time 

print

#hd_132Print on standard output 

print RCS Version

#hd_123version and emulation 

quiet

#hd_114quiet 
#hd_133Quiet mode 
#hd_171Quiet mode 
#hd_178Quiet mode 

Quiet mode

#hd_210Quiet Mode 

Quiete mode

#hd_158Quiet mode 
#hd_166Quiet mode 

rcs

#hd_43rcs -- change RCS file attributes 
#hd_92Tichy, Walter F. 

RCS commands

#hd_19Introduction to RCS commands 

RCS Version

#hd_174Version and Emulation 
#hd_181Version and Emulation 

rcsclean

#hd_55rcsclean -- clean up working files 

rcsdiff

#hd_63rcsdiff -- compare RCS revisions 

rcsfile

#hd_87Format of RCS file 

rcsmerge

#hd_69rcsmerge -- merge RCS versions 

remove

#hd_170No removing 

revision

#hd_109Check in revision 
#hd_127Check out revision 
#hd_172Revision for comparison 
#hd_179Revision for comparison 

Revision message

#hd_154Replace log message 

rlog

#hd_75rlog -- print log messages 

SCCS

#hd_91Rochkind, Marc J. 
#hd_94Glasser, Alan L. 

send result to standard out.

#hd_186Send to standard out 

set branch

#hd_103Default branch 

SIGPLAN

#hd_93Leblang, David B. and Chase, Robert P. 

Software Quality

#hd_94Glasser, Alan L. 

Standard output

#hd_209Standard output 

State

#hd_137State 

states

#hd_120states 
#hd_160States 

Strict Locking

#hd_152Strict Locking 

String-To-String Correction

#hd_101Tichy, Walter F. 

Substitution

#hd_37Keyword Substitution 

suffixes

#hd_124suffixes 
#hd_141Suffixes 
#hd_164Suffixes 
#hd_175Suffixes 
#hd_182Suffixes 
#hd_189Suffixes 
#hd_204Suffixes 

Support

#hd_99Tichy, Walter F. 

Symbolic

#hd_143Symbolic name 
#hd_156Override Symbolic name 

symbolic name

#hd_107symbolic name 

Symposium

#hd_93Leblang, David B. and Chase, Robert P. 

tag

#hd_107symbolic name 
#hd_143Symbolic name 
#hd_156Override Symbolic name 

time

#hd_135Checkout by date/time 

Time Zone

#hd_165Time Zone 
#hd_176Time zone 
#hd_190Time Zone 
#hd_205Time zone 

time zoone

#hd_125time zoone 

time/date

#hd_173Modification time 
#hd_180Modification time 

Tools

#hd_99Tichy, Walter F. 

TZ

#hd_125time zoone 

unlock

#hd_170No removing 

unlock a revision

#hd_111unlock a revision 

Unlock revision

#hd_168Unlock revision 

Unlock revsion

#hd_151Unlock revisions 

Version

#hd_126Version, Emulate RCS Version 
#hd_163Version 
#hd_167Version 
#hd_188Version 
#hd_203Version and Emulation 
#hd_211Version 

working

#hd_130Force overwriting working file 

working files

#hd_55rcsclean -- clean up working files 

Workstation

#hd_93Leblang, David B. and Chase, Robert P. 

zoone

#hd_125time zoone 
#hd_142Time Zoone 




