co man page on 4.4BSD
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.
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. 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 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 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. The numeric equivalent of a symbolic
field is specified with the -n option of the commands ci(1) and
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:
5.7 $ 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: 5.7 $. This option is useful to ignore differences
due to keyword substitution when comparing different revisions
of a file.
-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: 5.7 $ 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.
-kv Generate only keyword values for keyword strings. For example,
for the Revision keyword, generate the string 5.7 instead of
$Revision: 5.7 $. 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 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
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 val‐
ues 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
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 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 may 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.
-Vn 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 corre‐
spondents 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 generated
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 characterize RCS files. See ci(1) for details.
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.
$Date$ 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).
$Id$ Same as $Header$, except that the RCS filename is without a
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 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
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)
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.
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: 5.7; Release Date: 1991/08/19.
Copyright © 1982, 1988, 1989 by Walter F. Tichy.
Copyright © 1990, 1991 by Paul Eggert.
ci(1), ctime(3), date(1), ident(1), make(1), rcs(1), rcsdiff(1), rcsin‐
tro(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.
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.
GNU 1991/08/19 CO(1)
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