# CO - check out RCS revisions - man - [phpMan] > **TLDR:** Check out RCS revisions (retrieve working files from the Revision Control System). > - Check out the latest revision of a file (retrieves a read-only copy): `co {{path/to/file}}` - Check out a file with a lock for editing: `co -l {{path/to/file}}` - Check out a specific revision of a file: `co -r{{revision}} {{path/to/file}}` - Check out a file and overwrite it if it already exists: `co -f -l {{path/to/file}}` - Print a specific revision to `stdout` without creating a file: `co -p -r{{revision}} {{path/to/file}}` *Source: tldr-pages* --- [_CO_(1)](https://www.chedong.com/phpMan.php/man/CO/1/markdown) General Commands Manual [_CO_(1)](https://www.chedong.com/phpMan.php/man/CO/1/markdown) ## NAME co - check out RCS revisions ## SYNOPSIS **co **[_options_] _file_ ... ## DESCRIPTION **co **retrieves a revision from each RCS file and stores it into the corresponding working file. 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). 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**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown).) 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 restric‐ tions, 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 re‐ vision that satisfies all of them. If none of the selection options is specified, **co **re‐ trieves the latest revision on the default branch (normally the trunk, see the **-b **option of [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown)). A revision or branch number can be attached to any of the options **-f**, **-I**, **-l**, **-M**, ### -p -q -r -u -d -s -w 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). ## OPTIONS ### -r retrieves the latest revision whose number is less than or equal to _rev_. If _rev_ indi‐ cates a branch rather than a revision, the latest revision on that branch is re‐ trieved. If _rev_ is omitted, the latest revision on the default branch (see the **-b **op‐ tion of [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown)) is retrieved. If _rev_ is **$**, **co **determines the revision number from keyword values in the working file. Otherwise, a revision is composed of one or more numeric or symbolic fields separated by periods. If _rev_ begins with a period, then the default branch (normally the trunk) is prepended to it. If _rev_ is a branch number followed by a period, then the latest revision on that branch is used. The numeric equivalent of a symbolic field is specified with the **-n **option of the commands [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) and [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown). ### -l same as **-r**, except that it also locks the retrieved revision for the caller. ### -u same as **-r**, except that it unlocks the retrieved revision if it was locked by the caller. If _rev_ is omitted, **-u **retrieves the revision locked by the caller, if there is one; otherwise, it retrieves the latest revision on the default branch. ### -f forces the overwriting of the working file; useful in connection with **-q**. See also FILE MODES below. ### -kkv **vision **keyword. A locker's name is inserted in the value of the **Header**, **Id**, and **Locker **keyword strings only as a file is being locked, i.e. by **ci -l **and **co -l**. This is the default. ### -kkvl -kkv currently locked. ### -kk STITUTION below. For example, for the **Revision **keyword, generate the string **$Revi‐** **sion$ **instead of **$Revision: 5.10.1 $**. This option is useful to ignore differences due to keyword substitution when comparing different revisions of a file. Log messages are inserted after **$Log$ **keywords even if **-kk **is specified, since this tends to be more useful when merging changes. ### -ko checked in. For example, for the **Revision **keyword, generate the string **$Revision: 1.1** **$ **instead of **$Revision: 5.10.1 $ **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 -ko forms 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, [**rcsmerge**(1)](https://www.chedong.com/phpMan.php/man/rcsmerge/1/markdown) normally refuses to merge files when **-kb **is in effect. ### -kv word, generate the string **5.10.1 **instead of **$Revision: 5.10.1 $**. This can help gener‐ ate files in programming languages where it is hard to strip keyword delimiters like **$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**. ### -p 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. ### -q quiet mode; diagnostics are not printed. ### -I interactive mode; the user is prompted and questioned even if the standard input is not a terminal. ### -d_ 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 _date_s 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)](https://www.chedong.com/phpMan.php/man/ctime/3/markdown) + **LT** **Thu Jan 11 20:00:00 PST 1990 **output of [**date**(1)](https://www.chedong.com/phpMan.php/man/date/1/markdown) **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 as‐ sumed. For all other omitted fields, the lowest possible values are assumed. For ex‐ ample, 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. ### -M Set the modification time on the new working file to be the date of the retrieved re‐ vision. Use this option with care; it can confuse [**make**(1)](https://www.chedong.com/phpMan.php/man/make/1/markdown). ### -s_ retrieves the latest revision on the selected branch whose state is set to _state_. ### -S exists. Effectively, this means the user cannot check out the same revision twice. ### -T lock is added or removed. This option can suppress extensive recompilation caused by a [**make**(1)](https://www.chedong.com/phpMan.php/man/make/1/markdown) 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. ### -w 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 as‐ sumed. ### -j_ generates a new revision which is the join of the revisions on _joinlist_. This option is largely obsoleted by [**rcsmerge**(1)](https://www.chedong.com/phpMan.php/man/rcsmerge/1/markdown) 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_ de‐ notes 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 par‐ ticularly 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 revi‐ sion 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**(1)](https://www.chedong.com/phpMan.php/man/merge/1/markdown). 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 as‐ sumed. The options **-l **and **-u **lock or unlock _rev1_. ### -V ### -V_ ing 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 **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 revi‐ sion 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 ab‐ breviated dates of the form _yy_**/_**mm_**/_**dd_ and can also contain different white space and line prefixes in the substitution for **$Log$**. ### -x_ Use _suffixes_ to characterize RCS files. See [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) for details. ### -z_ time zone for _date_ in the **-d_**date_ option. The _zone_ should be empty, a numeric UTC off‐ set, 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; otherwise, times are output in ISO 8601 for‐ mat 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** The **-z **option does not affect dates stored in RCS files, which are always UTC. ## 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 **-z_**zone_ a numeric time zone offset is appended; otherwise, the date is UTC. ### $Header$ A standard header containing the full RCS file name, the revision number, the date and time, the author, the state, and the locker (if locked). With **-z_**zone_ a numeric time zone offset is appended to the date; otherwise, the date is UTC. **$Id$ **Same as **$Header$**, except that the RCS file name is without the directory components. ### $Locker$ 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 file name, the revision number, the author, and the date and time. With **-z_**zone_ 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 use‐ ful for accumulating a complete change log in a source file. Each inserted line is prefixed by the string that prefixes the **$Log$ **line. For exam‐ ple, 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 com‐ ment. 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 **gen‐ erates **$Name: Joe $**. Plain **co **generates just **$Name: $**. ### $RCSfile$ The RCS file name without directory components. ### $Revision$ The revision number assigned to the revision. ### $Source$ The full RCS file name. ### $State$ The state assigned to the revision with the **-s **option of [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown) or [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown). The following characters in keyword values are represented by escape sequences to keep key‐ word 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 permission is turned on, unless **-kv **is set or the file is checked out un‐ locked and locking is set to strict (see [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/1/markdown)). 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**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown) 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. 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, the working file name, and the revision number retrieved are written to the diagnostic output. The exit status is zero if and only if all operations were success‐ ful. ## 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 [**ci**(1)](https://www.chedong.com/phpMan.php/man/ci/1/markdown), [**ctime**(3)](https://www.chedong.com/phpMan.php/man/ctime/3/markdown), [**date**(1)](https://www.chedong.com/phpMan.php/man/date/1/markdown), [**ident**(1)](https://www.chedong.com/phpMan.php/man/ident/1/markdown), [**make**(1)](https://www.chedong.com/phpMan.php/man/make/1/markdown), [**rcs**(1)](https://www.chedong.com/phpMan.php/man/rcs/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. ## LIMITS Links to the RCS and working files are not preserved. There is no way to selectively suppress the expansion of keywords, except by writing them differently. In nroff and troff, this is done by embedding the null-character **\& **into the keyword. GNU RCS 5.10.1 2022-02-19 [_CO_(1)](https://www.chedong.com/phpMan.php/man/CO/1/markdown)