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CO(1)			     General Commands Manual			   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 corre-
     sponding working file.

     Pathnames matching an RCS suffix denote RCS files; all others denote  work-
     ing 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 lock-
     ing  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  re-
     quires  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 re-
     vision 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).

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 re-
	    trieved.  If rev is $, co determines the revision number  from  key-
	    word  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 nu-
	    meric 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:
	    5.13 $ 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  key-
	    word,  generate  the string $Revision$ instead of $Revision: 5.13 $.
	    This option is useful to ignore differences due to keyword substitu-
	    tion 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: 5.13 $ 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, rc-
	    smerge(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 5.13 instead of $Revision:
	    5.13 $.  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 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 Time (UTC):

		   8:00 pm lt
		   4:00 AM, Jan. 12, 1990	    default is UTC
		   1990-01-12 04:00:00+00	    ISO 8601 (UTC)
		   1990-01-11 20:00:00-08	    ISO 8601 (local time)
		   1990/01/12 04:00:00		    traditional RCS 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  Internet RFC 822
		   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  low-
	    est  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.

     -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  sup-
	    press 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 join-
	    list.   This  option  is largely obsoleted by rcsmerge(1) but is re-
	    tained 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  se-
	    lected  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 ances-
	    tor.  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  com-
	    mon 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 use-
	    ful 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  gen-
	    erated 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 substi-
	    tution for $Log$.

     -xsuffixes
	    Use suffixes to characterize RCS files.  See ci(1) for details.

     -zzone
	    specifies the date output format in keyword substitution, and speci-
	    fies 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  tradi-
	    tional  RCS  format of UTC without any time zone indication and with
	    slashes separating the parts of the date; otherwise, times are  out-
	    put  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	(default)
		   -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.

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 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  re-
     vision  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 the revision was checked in.  With -zzone a nu-
	    meric time zone offset is appended; otherwise, the date is UTC.

     $Header$
	    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  ap-
	    pended to the date; otherwise, the date is UTC.

     $Id$   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  con-
	    taining  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 lan-
	    guages with comments that go to the end of the line.  The convention
	    for other languages is to use a " * " prefix inside a multiline com-
	    ment.  For example, the initial log comment of a C	program  conven-
	    tionally is of the following form:

		   /*
		    * $Log$
		    */

	    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 ob-
	    solescent and should not be relied on.

     $Name$
	    The symbolic name used to check out the revision, if any.  For exam-
	    ple, co -rJoe  generates  $Name: Joe $.   Plain  co  generates  just
	    $Name:  $.

     $RCSfile$
	    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).

     The following characters in keyword values are represented  by  escape  se-
     quences to keep keyword strings well-formed.

	    char     escape sequence
	    tab      \t
	    newline  \n
	    space    \040
	    $	     \044
	    \	     \\

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 unless a revision number of $ is specified.

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.
     Manual Page Revision: 5.13; Release Date: 1995/06/01.
     Copyright (C) 1982, 1988, 1989 Walter F. Tichy.
     Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.

SEE ALSO
     rcsintro(1),  ci(1),  ctime(3),  date(1),	ident(1),  make(1),  rcs(1), rc-
     sclean(1), rcsdiff(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.

GNU				   1995/06/01				   CO(1)

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