       1mflock 4m22moptions24m 4mfileId24m ?4mstart24m? ?4mlength24m? ?4morigin24m?

              This  command places a lock on all or part of the file specified
              by 4mfileId24m.  The lock is either advisory or mandatory,  depending
              on  the  mode bits of the file.  The lock is placed beginning at
              relative byte offset 4mstart24m for 4mlength24m bytes.  If 4mstart24m or 4mlength0m
              is  omitted  or empty, zero is assumed.  If 4mlength24m is zero, then
              the lock always extents to end of file, even if the file  grows.
              If  4morigin24m is "1mstart22m", then the offset is relative to the begin-
              ning of the file. If it is "1mcurrent22m", it is relative to the cur-
              rent  access  position  in the file.  If it is "1mend22m", then it is
              relative to the end-of-file (a negative is before the EOF, posi-
              tive is after).  If 4morigin24m is omitted, 1mstart 22mis assumed.

              The following 4moptions24m are recognized:

              1m-read  22mPlace a read lock on the file.  Multiple processes may be
                     accessing the file with read-locks.

              1m-write 22mPlace a write lock on the file.  Only one process may  be
                     accessing a file if there is a write lock.

              1m-nowait0m
                     If specified, then the process will not block if the lock
                     can not be  obtained.   With  this  option,  the  command
                     returns 1 if the lock is obtained and 0 if it is not.

              See  your  system's  1mfcntl  22msystem  call  documentation for full
              details of the behavior of file locking.  If  locking  is  being
              done  on  ranges  of  a  file, it is best to use unbuffered file
              access (see the 1mfcntl 22mcommand).

              The 1mflock 22mcommand is not available on 1mWindows 9522m.  It is  avail-
              able on 1mWindows NT22m.
