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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.
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 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. 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: 5.8 $ 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: 5.8 $. 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 $Revision: 5.8 $ 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
5.8 instead of $Revision: 5.8 $. 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 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.
-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.
-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.
-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) 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 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 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
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
$Log$.
-xsuffixes
Use suffixes to characterize RCS files. See ci(1) for
details.
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 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:
$Author$
The login name of the user who checked in the revision.
$Date$
The date and time (UTC) the revision was checked in.
$Header$
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 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 (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.
$RCSfile$
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).
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 possible. 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.
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.
Revision Number: 5.8; Release Date: 1992/02/17.
Copyright 1982, 1988, 1989 by Walter F. Tichy.
Copyright 1990, 1991, 1992 by Paul Eggert.
SEE ALSO
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.
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.
BUGS
The -d option sometimes gets confused, and accepts no date
before 1970.