co
CO(1) 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 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 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 satis-
fies 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
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 revi-
sion, 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 connec-
tion with -q. See also FILE MODES below.
-kkv Generate keyword strings using the default form, e.g. $Revi-
sion: 5.13 $ 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.
-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: 5.13 $. 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 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: 5.13 $ if that is how the string appeared when the file
was checked in. This can be useful for file formats that can-
not 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 5.13 instead of
$Revision: 5.13 $. 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.
-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 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.
-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.
-S Turns on same user locks. When this is enabled the user cannot
check out the same file 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.
-w[login]
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.
-jjoinlist
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
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 use-
ful 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
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 or comments to identify a revision.
Initially, the user enters strings of the form $keyword$. On check-
out, co replaces these strings with strings of the form $key-
word:value$. 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 -zzone a
numeric time zone offset is appended; otherwise, the date is
UTC.
$Header$
A standard header containing the full pathname of the RCS file,
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 filename is without a
path.
$Locker$
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 filename, 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 “ ∗ ”
prefix inside a multiline comment. 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 generates $Name: Joe $. Plain co generates
just $Name: $.
$RCSfile$
The name of the RCS file without a path.
$Revision$
The revision number assigned to the revision.
$Source$
The full pathname of the RCS file.
$State$
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
$ \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 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 possi-
ble. 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) 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.
See ci(1) for details.
DIAGNOSTICS
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.
IDENTIFICATION
Author: Walter F. Tichy.
Manual Page Revision: 5.13; Release Date: 1995/06/01.
Copyright © 1982, 1988, 1989 Walter F. Tichy.
Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
SEE ALSO
rcsintro(1), ci(1), ctime(3), date(1), ident(1), make(1), rcs(1),
rcsclean(1), rcsdiff(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.
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 1995/06/01 CO(1)
