co - check out RCS revisions
co [options] file...
retrieves the latest revision whose number is less than or equal to rev. If rev indicates a branch rather than a revision, the latest revi-
sion 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. The numeric equivalent of a symbolic field is specified with the -n option of the com-
mands ci(1) and rcs(1). same as -r, except that it also locks the retrieved revision for the caller. 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. Generate keyword strings using the default form, e.g. $Revision: 184.108.40.206 $ 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. Like -kkv, except that a locker's name is always inserted if the given revision is currently locked. Generate
only keyword names in keyword strings; omit their values. See KEYWORD SUBSTITUTION below. For example, for the Revision keyword, generate
the string $Revision$ instead of $Revision: 220.127.116.11$. This option is useful to ignore differences due to keyword substitution when compar-
ing different revisions of a file. Generate the old keyword string, present in the working file just before it was checked in. For exam-
ple, for the Revision keyword, generate the string $Revision: 1.1 $ instead of $Revision: 18.104.22.168 $ if that is how the string appeared when
the file was checked in. This can be useful for binary file formats that cannot tolerate any changes to substrings that happen to take the
form of keyword strings. Generate only keyword values for keyword strings. For example, for the Revision keyword, generate the string
22.214.171.124 instead of $Revision: 126.96.36.199 $. 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. 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. retrieves the latest
revision on the selected branch whose checkin date/time is less than or equal to date. The date and time may 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 note: default is UTC 1990/01/12 04:00:00 RCS date 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 Fri-JST, 1990, 1pm Jan 12 12-January-1990, 04:00-WET
Most fields in the date and time may be defaulted. The default time zone is UTC. 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 example, 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 confuse make(1). retrieves the latest
revision on the selected branch whose state is set to state. 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 com-
The joinlist is a comma-separated list of pairs of the form rev2 :rev3, where rev2 and rev3 are (symbolic or numeric) revision num-
bers. 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 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
For the initial pair, rev2 may be omitted. The default is the common ancestor. If any of the arguments indicate branches, the lat-
est revisions on those branches are assumed. The options -l and -u lock or unlock rev1. Emulate RCS version n, where n may be 3, 4,
or 5. This may be useful when interchanging RCS files with others who are running older versions of RCS. To see which version of RCS
your correspondents are running, 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 gener-
ated while emulating version 3 will lose its default branch. An RCS revision generated while emulating version 4 or earlier will
have a timestamp that is off by up to 13 hours. A revision extracted while emulating version 4 or earlier will contain dates of the
form yy/mm/dd instead of yyyy/mm/dd and may also contain different white space in the substitution for $Log$. Use suffixes to char-
acterize RCS files. See ci(1) for details.
co retrieves a revision from each RCS file and stores it into the corresponding working file.
Pathnames 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 may 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 may 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 may 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
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 may 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. The date and time (UTC) the revision was
checked in. A standard header containing the full pathname of the RCS file, the revision number, the date (UTC), the author, the state,
and the locker (if locked). Same as $Header$, except that the RCS filename is without a path. The login name of the user who locked the
revision (empty if not locked). The log message supplied during checkin, preceded by a header containing the RCS filename, the revision
number, the author, and the date (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. The name of the RCS file without a path. The revision number
assigned to the revision. The full pathname of the RCS file. The state assigned to the revision with the -s option of rcs(1) or ci(1).
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 (see rcs(1)).
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.
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.
The -d option sometimes gets confused, and accepts no date before 1970.
co accesses files much as ci(1) does, except that it does not need to read the working file.
options prepended to the argument list, separated by spaces. See ci(1) for details.
The RCS pathname, the working pathname, 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.
Revision Number: 188.8.131.52; Release Date: 1993/10/07.
Copyright (C) 1982, 1988, 1989 by Walter F. Tichy.
Copyright (C) 1990, 1991 by Paul Eggert.
ci(1), ctime(3), date(1), ident(1), make(1), rcs(1), rcsdiff(1), rcsintro(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.