CO(1) General Commands Manual CO(1)
co - check out RCS revisions
co [options] file ...
co retrieves a revision from each RCS file and stores it into the cor-
responding working file.
Filenames matching an RCS suffix denote RCS files; all others denote
working files. Names are paired as explained in ci(1).
Revisions of an RCS file can be checked out locked or unlocked. Lock-
ing 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).) 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 rcs(1)). 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 sin-
gle 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
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
rcs(1)) 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 revi-
sion on that branch is used. The numeric equivalent of a sym-
bolic field is specified with the -n option of the commands
ci(1) and rcs(1).
same as -r, except that it also locks the retrieved revision for
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.
forces the overwriting of the working file; useful in connection
with -q. See also FILE MODES below.
-kkv Generate keyword strings using the default form, e.g. $Revision:
5.9.4 $ 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
-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 val-
ues. See KEYWORD SUBSTITUTION below. For example, for the
Revision keyword, generate the string $Revision$ instead of
$Revision: 5.9.4 $. 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
-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 $Revi-
sion: 5.9.4 $ 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 ini-
tialize an RCS file intended to be used for binary files. Also,
on all hosts, rcsmerge(1) 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 5.9.4 instead of
$Revision: 5.9.4 $. This can help generate files in programming
languages where it is hard to strip keyword delimiters like
$Revision: $ from a string. However, further keyword substitu-
tion 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.
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; diagnostics are not printed.
interactive mode; the user is prompted and questioned even if
the standard input is not a terminal.
-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 signifi-
cant). 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.
Set the modification time on the new working file to be the date
of the retrieved revision. Use this option with care; it can
retrieves the latest revision on the selected branch whose state
is set to state.
-S Enable self-same mode. In this mode, the owner of a lock is
unimportant, just that it exists. Effectively, this means the
user cannot check out the same revision twice.
-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(1) depen-
dency 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.
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.
generates a new revision which is the join of the revisions on
joinlist. This option is largely obsoleted by rcsmerge(1) 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) revi-
sion numbers. For the initial such pair, rev1 denotes the revi-
sion 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(1).
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.
-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 corre-
spondents 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 revision generated while emulating ver-
sion 4 or earlier has a time stamp that is off by up to 13
hours. A revision extracted while emulating version 4 or ear-
lier contains abbreviated dates of the form yy/mm/dd and can
also contain different white space and line prefixes in the sub-
stitution for $Log$.
Use suffixes to characterize RCS files. See ci(1) for details.
-zzone specifies the date output format in keyword substitution, and
specifies the default time zone for date in the -ddate 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;
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 1990/01/12 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.
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:
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
A standard header containing the full RCS file name, the revi-
sion 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 UTC.
$Id$ Same as $Header$, except that the RCS file name is without the
The login name of the user who locked the revision (empty if not
$Log$ 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 -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 " * " pre-
fix inside a multiline comment. For example, the initial log
comment of a C program conventionally is of the following form:
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: $.
The RCS file name without directory components.
The revision number assigned to the revision.
The full RCS file name.
The state assigned to the revision with the -s option of rcs(1)
The following characters in keyword values are represented by escape
sequences to keep keyword strings well-formed.
char escape sequence
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 unlocked and locking is set to strict
If a file with the name of the working file exists already and has
write permission, co aborts the checkout, asking beforehand if possi-
ble. If the existing working file is not writable or -f is given, the
working file is deleted without asking.
co accesses files much as ci(1) does, except that it does not need to
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. Use-
ful 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 kilo-
bytes). 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.
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 successful.
Author: Walter F. Tichy.
Manual Page Revision: 5.9.4; Release Date: 2015-06-21.
Copyright (C) 2010-2015 Thien-Thi Nguyen.
Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
Copyright (C) 1982, 1988, 1989 Walter F. Tichy.
ci(1), ctime(3), date(1), ident(1), make(1), rcs(1), rcsclean(1), rcsd-
iff(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
should give you access to the complete manual. Additionally, the RCS
has news and links to the latest release, development site, etc.
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 5.9.4 2015-06-21 CO(1)
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