CO(1) General Commands Manual CO(1)
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).
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 revi‐
sion 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 (nor‐
mally 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
single 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[rev]
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 revision on that branch is used. The numeric equivalent of a symbolic field is specified
with the -n option of the commands ci(1) and rcs(1).
-l[rev]
same as -r, except that it also locks the retrieved revision for the caller.
-u[rev]
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[rev]
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: 5.9.0 $ 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 default.
-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 initialize 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 5.9.0 instead of $Revision: 5.9.0 $. This can help generate 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[rev]
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[rev]
quiet mode; diagnostics are not printed.
-I[rev]
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 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 assumed. For all other omitted fields, the lowest possible values are assumed. For exam‐
ple, 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[rev]
Set the modification time on the new working file to be the date of the retrieved revision. Use this
option with care; it can confuse make(1).
-sstate
retrieves the latest revision on the selected branch whose state is set to state.
login. If the argument login is omitted, the caller's login is assumed.
-jjoinlist
generates a new revision which is the join of the revisions on joinlist. This option is largely obso‐
leted 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 (sym‐
bolic or numeric) revision numbers. For the initial such pair, rev1 denotes the revision selected by
the above options -f, ..., -w. For all other pairs, rev1 denotes the revision generated by the previ‐
ous 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 over‐
laps as described in merge(1).
For the initial pair, rev2 can be omitted. The default is the common ancestor. If any of the argu‐
ments 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 correspondents are run‐
ning, 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 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 abbreviated dates of the form yy/mm/dd and can also con‐
tain different white space and line prefixes in the substitution for $Log$.
-xsuffixes
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.
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
$Date$ The date and time the revision was checked in. With -zzone 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 -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 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 revi‐
sion 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 lan‐
guages with comments that go to the end of the line. The convention for other languages is to use a “
∗ ” prefix inside a multiline comment. For example, the initial log comment of a C program convention‐
ally 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 generates
$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) or ci(1).
The following characters in keyword values are represented by escape sequences to keep keyword strings well-
formed.
char escape sequence
tab \t
newline \n
space \040
FILES
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.
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
An integer lim, measured in kilobytes, specifying the threshold under which commands will try to use
memory-based operations for processing the RCS file. (For RCS files of size lim kilobytes or greater,
RCS will use the slower standard input/output routines.) Default value is 256.
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 out‐
put. The exit status is zero if and only if all operations were successful.
IDENTIFICATION
Author: Walter F. Tichy.
Manual Page Revision: 5.9.0; Release Date: 2014-06-10.
Copyright © 2010-2013 Thien-Thi Nguyen.
Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
Copyright © 1982, 1988, 1989 Walter F. Tichy.
SEE ALSO
ci(1), ctime(3), date(1), ident(1), make(1), rcs(1), rcsclean(1), rcsdiff(1), rcsmerge(1), rlog(1), rcs‐
file(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 prop‐
erly installed at your site, the command
info rcs
should give you access to the complete manual. Additionally, the RCS homepage:
http://www.gnu.org/software/rcs/
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.
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