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 corresponding working file. Each file name ending in ,v is taken to be an RCS file; all other files are assumed to be working files. If only a working file is given, co tries to find the corresponding RCS file in the directory ./RCS and then in the current directory. For more details, see FILE NAMING below.

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, -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. 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 latest revision locked by the caller; if no such lock exists, 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: $ 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: $. 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: $ 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 instead of $Revision: $. 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 GMT):

        8:00 pm lt
        4:00 AM, Jan. 12, 1990	note: default is GMT
        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 GMT. 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 GMT of the 20th of the GMT time zone's current month and year. The date/time must be quoted if it contains spaces.

-sstate
    retrieves the latest revision on the selected branch whose state is set to state.

-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 prints a warning and includes the overlapping sections, delimited by the lines <<<<<<< rev1, =======, and >>>>>>> rev3.

    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 $Log$.

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 (GMT) the revision was checked in.

$Header$
    A standard header containing the full pathname of the RCS file, the revision number, the date (GMT), the author, the state, and the locker (if locked).

$Id$
    Same as $Header$, except that the RCS file name 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 file name, the revision number, the author, and the date (GMT). 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 NAMING
Pairs of RCS files and working files may be specified in three ways (see also the example section).

1) Both the RCS file and the working file are given. The RCS file name is of the form path1/workfile,v and the working file name is of the form path2/workfile where path1/ and path2/ are (possibly different or empty) paths and workfile is a file name.

2) Only the RCS file is given. Then the working file is created in the current directory and its name is derived from the name of the RCS file by removing path1/ and the suffix ,v.

3) Only the working file is given. Then co looks for an RCS file of the form path2/RCS/workfile,v or path2/workfile,v (in this order).

If the RCS file is specified without a path in 1) and 2), then co looks for the RCS file first in the directory ./RCS and then in the current directory.

EXAMPLES
Suppose the current directory contains a subdirectory RCS with an RCS file io.c,v. Then all of the following commands retrieve the latest revision from RCS/io.c,v and store it into io.c.

    co  io.c;    co  RCS/io.c,v;   co  io.c,v;
    co  io.c  RCS/io.c,v;    co  io.c  io.c,v;
    co  RCS/io.c,v  io.c;    co  io.c,v  io.c;

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.

DIAGNOSTICS
The RCS file name, the working file name, 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: ; Release Date: .
Copyright © 1982, 1988, 1989 by Walter F. Tichy.
Copyright © 1990 by Paul Eggert.

SEE ALSO
ci(1), ctime(3), date(1), ident(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.