co - check out RCS revisions
co [options] file ...
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 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 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 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).
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).
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.
-kkv Generate keyword strings using the default form,
e.g. $Revision: 1.1 $ 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 values. See KEYWORD SUBSTITUTION below.
For example, for the Revision keyword, generate the
string $Revision$ instead of $Revision: 1.1 $.
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 $Revision: 1.1 $
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 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 1.1 instead of $Revision: 1.1 $. 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.
-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
8:00 pm lt
4:00 AM, Jan. 12, 1990 default is
1990-01-12 04:00:00+00 ISO 8601
1990-01-11 20:00:00-08 ISO 8601
1990/01/12 04:00:00 traditional
Thu Jan 11 20:00:00 1990 LT output of
ctime(3) + LT
Thu Jan 11 20:00:00 PST 1990 output of
Fri Jan 12 04:00:00 GMT 1990
Thu, 11 Jan 1990 20:00:00 -0800 Internet
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 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 confuse make(1).
retrieves the latest revision on the selected
branch whose state is set to state.
-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) dependency 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
The joinlist is a comma-separated list of pairs of
the form rev2:rev3, where rev2 and rev3 are (symbolic
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
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 correspondents 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 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 contain different white space
and line prefixes in the substitution for $Log$.
Use suffixes to characterize RCS files. See ci(1)
-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
-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 $key-
word:value$ 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 UTC.
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.
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:
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 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 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 (see
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
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. 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
Author: Walter F. Tichy.
Manual Page Revision: 1.1; Release Date: 1996/08/12.
Copyright (C) 1982, 1988, 1989 Walter F. Tichy.
Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul
rcsintro(1), ci(1), ctime(3), date(1), ident(1), make(1),
rcs(1), rcsclean(1), rcsdiff(1), rcsmerge(1), rlog(1),
Walter F. Tichy, RCS--A System for Version Control,
Software--Practice & Experience 15, 7 (July 1985),
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-characte&
into the keyword.
GNU 1996/08/12 9 [ Back ]