# man > rcs(1) > **TLDR:** Revision Control System - manage RCS file attributes. > - Unlock a revision locked by another user (requires access): `rcs -u {{path/to/file}}` - Lock a specific revision of a file: `rcs -l{{revision}} {{path/to/file}}` - Set the strict locking mode (require lock for check-in): `rcs -L {{path/to/file}}` - Add or replace a log message for a specific revision: `rcs -m{{revision}}:"{{new_message}}" {{path/to/file}}` - Delete a specific revision from the RCS file: `rcs -o{{revision}} {{path/to/file}}` *Source: tldr-pages* --- [_RCS_(1)](https://www.chedong.com/phpMan.php/man/RCS/1/markdown) General Commands Manual [_RCS_(1)](https://www.chedong.com/phpMan.php/man/RCS/1/markdown) ## NAME rcs - change RCS file attributes ## SYNOPSIS **rcs _**options_ _file_ ... ## DESCRIPTION **rcs **creates new RCS files or changes attributes of existing ones. An RCS file contains mul‐ tiple revisions of text, an access list, a change log, descriptive text, and some control at‐ tributes. 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)](https://www.chedong.com/phpMan.php/man/ci/1/markdown). Revision numbers use the syntax described in [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown). ## OPTIONS ### -i 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. ### -a_ Append the login names appearing in the comma-separated list _logins_ to the access list of the RCS file. ### -A_ Append the access list of _oldfile_ to the access list of the RCS file. ### -e 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. ### -b Set the default branch to _rev_. If _rev_ is omitted, the default branch is reset to the (dynamically) highest branch on the trunk. ### -c_ 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)](https://www.chedong.com/phpMan.php/man/co/1/markdown)). 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. ### -k_ Set the default keyword substitution to _subst_. The effect of keyword substitution is described in [**co**(1)](https://www.chedong.com/phpMan.php/man/co/1/markdown). Giving an explicit **-k **option to **co**, **rcsdiff**, and **rcsmerge **over‐ rides this default. Beware **rcs -kv**, because **-kv **is incompatible with **co -l**. Use **rcs -kkv **to restore the normal default keyword substitution. ### -l 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). ### -u 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. Nor‐ mally, only the locker of a revision can unlock it. Somebody else unlocking a revi‐ sion 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 so‐ licited from the breaker. The commentary is terminated by end-of-file or by a line containing **. **by itself. ### -L empt from locking for checkin. This option should be used for files that are shared. ### -U 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. ### -m_ Replace revision _rev_'s log message with _msg_. If _msg_ is omitted, it defaults to "*** empty log message ***". ### -M sual use; it is meant for programs that warn users by other means, and invoke **rcs -u** only as a low-level lock-breaking operation. ### -n_ 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 al‐ ready associated with another number. If _rev_ is symbolic, it is expanded before asso‐ ciation. 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 con‐ trasts with **rcs -n_**name_**:$ RCS/* **which associates _name_ with the revision numbers ex‐ tracted from keyword strings in the corresponding working files. ### -N_ Act like **-n**, except override any previous assignment of _name_. ### -o_ deletes (“outdates”) the revisions given by _range_. A range consisting of a single re‐ vision 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 con‐ taining _rev_. None of the outdated revisions can have branches or locks. ### -q ### -I ### -s_ Set the state attribute of the revision _rev_ to _state_. If _rev_ is a branch number, as‐ sume the latest revision on that branch. If _rev_ is omitted, assume the latest revi‐ sion 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 de‐ fault, [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) sets the state of a revision to **Exp**. ### -t 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 it‐ self. Prompt for the text if interaction is possible; see **-I**. With **-i**, descriptive text is obtained even if **-t **is not given. ### -t-_ Write descriptive text from the _string_ into the RCS file, deleting the existing text. ### -T tion can suppress extensive recompilation caused by a [**make**(1)](https://www.chedong.com/phpMan.php/man/make/1/markdown) dependency of some copy of the working file on the RCS file. Use this option with care; it can suppress re‐ compilation 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. ### -V ### -V_ ### -x_ Use _suffixes_ to characterize RCS files. See [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) for details. ### -z_ patibility with other RCS commands. At least one explicit option must be given, to ensure compatibility with future planned ex‐ tensions to the **rcs **command. ## COMPATIBILITY The **-b_**rev_ option generates an RCS file that cannot be parsed by RCS version 3 or earlier. The **-k_**subst_ options (except **-kkv**) generate an RCS file that cannot be parsed by RCS version 4 or earlier. Use **rcs -V_**n_ 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. ## FILES **rcs **accesses files much as [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) does, except that it uses the effective user for all ac‐ cesses, 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. ## 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**. **RCS_MEM_LIMIT** 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''. Other‐ wise (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. **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 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. ## IDENTIFICATION 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. ## SEE ALSO [**co**(1)](https://www.chedong.com/phpMan.php/man/co/1/markdown), [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown), [**ident**(1)](https://www.chedong.com/phpMan.php/man/ident/1/markdown), [**rcsclean**(1)](https://www.chedong.com/phpMan.php/man/rcsclean/1/markdown), [**rcsdiff**(1)](https://www.chedong.com/phpMan.php/man/rcsdiff/1/markdown), [**rcsmerge**(1)](https://www.chedong.com/phpMan.php/man/rcsmerge/1/markdown), [**rlog**(1)](https://www.chedong.com/phpMan.php/man/rlog/1/markdown), [**rcsfile**(5)](https://www.chedong.com/phpMan.php/man/rcsfile/5/markdown). 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)](https://www.chedong.com/phpMan.php/man/info/1/markdown) 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. ## 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 sup‐ ports 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. GNU RCS 5.10.1 2022-02-19 [_RCS_(1)](https://www.chedong.com/phpMan.php/man/RCS/1/markdown)