# 2.11BSD#431 - /usr/new/man/cat1/co.0

    CO(1)		    UNIX Programmer's Manual		    CO(1)

    NAME
         co - check out RCS revisions

    SYNOPSIS
         co [ options ] file ...

    DESCRIPTION
         Co retrieves revisions from RCS files.  Each file name end-
         ing 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 remov-
         ing 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., com-
         piling) need not be locked. A revision checked out for edit-
         ing 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 sub-
         ject 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,

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         author, and state retrieve a revision on the selected
         branch. The selected branch is either derived from the revi-
         sion 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 sub-
         stitution (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 revi-
    		sion 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 revi-
    		sion on that branch is retrieved.  Rev is com-
    		posed of one or more numeric or symbolic fields
    		separated by `.'. The numeric equivalent of a
    		symbolic field is specified with the -n option of

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    		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 omit-
    		ted, 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 com-
         ments 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

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         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 revi-
    		  sion (empty if not locked).

         $Log$	  The log message supplied during checkin, pre-
    		  ceded 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 com-
         mands 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

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         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 permis-
         sion (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: 3.1 ; Release Date: 83/04/04 .
         Copyright (C) 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 Inter-
         national 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 dif-
         ferently. 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 `.'.

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