CO(1)

NAME
co - check out RCS revisions

SYNOPSIS
co [ options ] file ...

DESCRIPTION
Co retrieves revisions from RCS files. Each file name ending in `,v' is taken to be an RCS file. All other files are assumed to be working files. Co retrieves a revision from each RCS file and stores it into the corresponding working file.

Pairs of RCS files and working files may be specified in 3 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 the name of the RCS file is derived from the name of the working file by removing path2/ and appending the suffix `,v'.

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

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. Locking a revision currently locked by another user fails. (A lock may be broken with the rcs (1) command.) Co with locking 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. Co without locking is not subject to accesslist restrictions.

A revision is selected by number, checkin date/time, author, or state. If none of these options are specified, the latest revision on the trunk is retrieved. When the options are applied in combination, the latest revision that satisfies all of them is retrieved. The options for date/time, author, and state retrieve a revision on the selected branch. The selected branch is either derived from the revision number (if given), or is the highest branch on the trunk. A revision number may be attached to one of the options -l, -p, -q, or -r.

A co command applied to an RCS file with no revisions creates a zero-length file. Co always performs keyword substitution (see below).

-l[rev]
    locks the checked out revision for the caller. If omitted, the checked out revision is not locked. See option -r for handling of the revision number rev.

-p[rev]
    prints the retrieved revision on the std. 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.

-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 and are converted to local time. Examples of formats for date:
    22-April-1982, 17:20-CDT,
    2:25 AM, Dec. 29, 1983,
    Tue-PDT, 1981, 4pm Jul 21         (free format),
    Fri, April 16 15:52:25 EST 1982 (output of ctime).
    Most fields in the date and time may be defaulted. Co determines the defaults 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 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 of the 20th of the current month and current year. The date/time must be quoted if it contains spaces.

-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. Rev is composed of one or more numeric or symbolic fields separated by `.'. The numeric equivalent of a symbolic field is specified with the -n option of the commands ci and rcs.

-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. 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 options -l, ..., -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. If the option -l is present, the initial rev1 is locked.

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.

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.

$Header$
    A standard header containing the RCS file name, the revision number, the date, the author, and the state.

$Locker$
    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. 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.

$Revision$
    The revision number assigned to the revision.

$Source$
    The full pathname of the RCS file.

$State$
    The state assigned to the revision with rcs -s or ci -s.

DIAGNOSTICS
The RCS file name, the working file name, and the revision number retrieved are written to the diagnostic output. The exit status always refers to the last file checked out, and is 0 if the operation was successful, 1 otherwise.

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 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 if -q is given, or asks whether to abort if -q is not given. If the existing working file is not writable, it is deleted before the checkout.

FILES
The caller of the command must have write permission in the working directory, read permission for the RCS file, and either read permission (for reading) or read/write permission (for locking) in the directory which contains the RCS file.

A number of temporary files are created. A semaphore file is created in the directory of the RCS file to prevent simultaneous update.

IDENTIFICATION
Author: Walter F. Tichy, Purdue University, West Lafayette, IN, 47907.

Revision Number: ; Release Date: .

Copyright © 1982 by Walter F. Tichy.

SEE ALSO
ci (1), ident(1), rcs (1), rcsdiff (1), rcsintro (1), rcsmerge (1), rlog (1), rcsfile (5), sccstorcs (8).

Walter F. Tichy, "Design, Implementation, and Evaluation of a Revision Control System," in Proceedings of the 6th International Conference on Software Engineering, IEEE, Tokyo, Sept. 1982.

LIMITATIONS
The option -d gets confused in some circumstances, and accepts no date before 1970. There is no way to 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 option -j does not work for files that contain lines with a single `.'.