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RCS(1) General Commands Manual RCS(1)


rcs - change RCS file attributes


rcs options file ...


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.

Filenames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in ci(1). Revision numbers use the syntax described in ci(1).


Create and initialize a new RCS file, but do not deposit any revision. If the RCS file name has no directory component, 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 the login names appearing in the comma-separated list logins to the access list of the RCS file.
Append the access list of oldfile to the access list of the RCS file.
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.
Set the default branch to rev. If rev is omitted, the default branch is reset to the (dynamically) highest branch on the trunk.
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 file name.

This option is obsolescent, since RCS normally uses the preceding $Log$ line's prefix when inserting log lines during checkout (see co(1)). 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.

Set the default keyword substitution to subst. The effect of keyword substitution is described in co(1). 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 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 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. If RCS was configured --with-mailer, then 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.
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.
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 revision rev's log message with msg. If msg is omitted, it defaults to "*** empty log message ***".
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.
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 -nname: RCS/* associates name with the current latest revision of all the named RCS files; this contrasts with rcs -nname:$ RCS/* which associates name with the revision numbers extracted from keyword strings in the corresponding working files.
Act like -n, except override any previous assignment of name.
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.
Run quietly; do not print diagnostics.
Run interactively, even if the standard input is not a terminal.
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, ci(1) sets the state of a revision to Exp.
Write descriptive text from the contents of the named file into the RCS file, deleting the existing text. The file name 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. With -i, descriptive text is obtained even if -t is not given.
Write descriptive text from the string into the RCS file, deleting the existing text.
Preserve the modification time on the RCS file unless a revision is removed. This option can suppress extensive recompilation caused by a make(1) 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.
Print RCS's version number.
Emulate RCS version n. See co(1) for details.
Use suffixes to characterize RCS files. See ci(1) for details.
Use zone as the default time zone. This option has no effect; it is present for compatibility with other RCS commands.

At least one explicit option must be given, to ensure compatibility with future planned extensions to the rcs command.


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 file name.


rcs accesses files much as ci(1) 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 the working file unless a revision number of $ is specified.


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.
Normally, for speed, commands either memory map or copy into memory the RCS file if its size is less than the memory-limit, currently defaulting to ``unlimited''. Otherwise (or if the initially-tried speedy ways fail), the commands fall back to using standard i/o routines. You can adjust the memory limit by setting RCS_MEM_LIMIT to a numeric value lim (measured in kilobytes). An empty value is silently ignored. As a side effect, specifying RCS_MEM_LIMIT inhibits fall-back to slower routines.
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.


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


Author: Walter F. Tichy.
Manual Page Revision: 5.10.1; Release Date: 2022-02-19.
Copyright © 2010-2022 Thien-Thi Nguyen.
Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
Copyright © 1982, 1988, 1989 Walter F. Tichy.


co(1), ci(1), ident(1), rcsclean(1), rcsdiff(1), rcsmerge(1), rlog(1), rcsfile(5).

Walter F. Tichy, RCS--A System for Version Control, Software--Practice & Experience 15, 7 (July 1985), 637-654.

The full documentation for RCS is maintained as a Texinfo manual. If the info(1) and RCS programs are properly installed at your site, the command

info rcs

should give you access to the complete manual. Additionally, the RCS homepage:

has news and links to the latest release, development site, etc.


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.

2022-02-19 GNU RCS 5.10.1