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CO(1)			    General Commands Manual			 CO(1)

       co - check out RCS revisions

       co [options] file ...

       co  retrieves a revision	from each RCS file and stores it into the cor-
       responding 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 can be	checked	out locked or unlocked.	 Lock-
       ing a revision prevents overlapping updates.  A	revision  checked  out
       for  reading or processing (e.g., compiling) need not be	locked.	 A re-
       vision 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	 can  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  re-
       trieves	the latest revision on the default branch (normally the	trunk,
       see the -b option of rcs(1)).  A	revision or branch number can  be  at-
       tached  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 be-

	      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.  If	rev begins with	a period, then the de-
	      fault 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 numeric equivalent  of  a  symbolic
	      field  is	specified with the -n option of	the commands ci(1) and

	      same as -r, except that it also locks the	retrieved revision for
	      the caller.

	      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.

	      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:
	      1.6 $ 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

       -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  val-
	      ues.   See KEYWORD SUBSTITUTION below.  For example, for the Re-
	      vision keyword, generate the string $Revision$ instead of	$Revi-
	      sion: 1.6	$.  This option	is useful to ignore differences	due to
	      keyword substitution 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	 merg-
	      ing 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	$Revi-
	      sion: 1.6	$ 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  ini-
	      tialize an RCS file intended to be used for binary files.	 Also,
	      on all hosts, rcsmerge(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  1.6  instead  of
	      $Revision:  1.6  $.  This	can help generate files	in programming
	      languages	where it is hard to strip keyword delimiters like $Re-
	      vision: $	 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 los-
	      ing 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.

	      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.

	      quiet mode; diagnostics are not printed.

	      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  signifi-
	      cant).   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  as-
	      sumed.   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.

	      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).

	      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)	depen-
	      dency  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.

	      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.

	      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) revi-
	      sion numbers.  For the initial such pair,	rev1 denotes the revi-
	      sion  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 can 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.

       -V     Print RCS's version number.

       -Vn    Emulate RCS version n, where n can be 3, 4, or 5.	 This  can  be
	      useful  when interchanging RCS files with	others who are running
	      older versions of	RCS.  To see which version of RCS your	corre-
	      spondents	 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	generated while	emulating ver-
	      sion 4 or	earlier	has a time stamp that  is  off	by  up	to  13
	      hours.   A  revision extracted while emulating version 4 or ear-
	      lier contains abbreviated	dates of the  form  yy/mm/dd  and  can
	      also contain different white space and line prefixes in the sub-
	      stitution	for $Log$.

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

       -zzone specifies	the date output	format in  keyword  substitution,  and
	      specifies	 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 traditional RCS format of UTC without any time zone in-
	      dication and with	slashes	separating the parts of	the date; oth-
	      erwise, times are	output in ISO 8601 format with time zone indi-
	      cation.  For example, if local time is January 11, 1990, 8pm Pa-
	      cific 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.

       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  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:

	      The login	name of	the user who checked in	the revision.

       $Date$ The date and time	the revision was checked in.   With  -zzone  a
	      numeric  time  zone  offset  is appended;	otherwise, the date is

	      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	appended to the	date; otherwise, the date is UTC.

       $Id$   Same  as	$Header$,  except  that	 the RCS filename is without a

	      The login	name of	the user who locked the	revision (empty	if not

       $Log$  The  log	message	 supplied during checkin, preceded by a	header
	      containing 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 af-
	      ter $Log:...$.  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: $",  RCS  prefixes	each line of the log with "// ".  This
	      is useful	for languages with comments that go to the end of  the
	      line.  The convention for	other languages	is to use a " *	" pre-
	      fix inside a multiline comment.  For example,  the  initial  log
	      comment of a C program conventionally 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,  in-
	      serted  log  lines  contain  a space instead of /	or (; however,
	      this usage is obsolescent	and should not be relied on.

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

	      The name of the RCS file without a path.

	      The revision number assigned to the revision.

	      The full pathname	of the RCS file.

	      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
       sequences to keep keyword strings well-formed.

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

       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	possi-
       ble.   If the existing working file is not writable or -f is given, the
       working file is deleted without asking.

       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.

	      options  prepended  to  the  argument list, separated by spaces.
	      See ci(1)	for details.

       The RCS pathname, the working pathname, and  the	 revision  number  re-
       trieved	are written to the diagnostic output.  The exit	status is zero
       if and only if all operations were successful.

       Author: Walter F. Tichy.
       Manual Page Revision: 1.6; Release Date:	1999/08/27.
       Copyright (C) 1982, 1988, 1989 Walter F.	Tichy.
       Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995	Paul Eggert.

       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.

       Links to	the RCS	and working files are not preserved.

       There is	no way to selectively suppress the expansion of	keywords,  ex-
       cept  by	writing	them differently.  In nroff and	troff, this is done by
       embedding the null-character \& into the	keyword.

GNU				  1999/08/27				 CO(1)


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