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CO(1)									 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 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
       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	 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
       retrieves  the  latest  revision	 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 sin-
       gle  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.  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
	      default branch (normally the trunk) is prepended to it.  If  rev
	      is  a  branch number followed by a period, then the latest revi-
	      sion on that branch is used.  The numeric equivalent of  a  sym-
	      bolic  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  val-
	      ues.   See  KEYWORD  SUBSTITUTION	 below.	  For example, for the
	      Revision keyword, generate  the  string  $Revision$  instead  of
	      $Revision:  5.13 $.  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
	      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 $Revi-
	      sion: 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  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  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 substitu-
	      tion 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  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
	      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.

       -S     Turns on same user locks.	 When this is enabled the user	cannot
	      check out the same file twice.

       -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.

       -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)	 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 $Log$.

       -xsuffixes
	      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
	      indication  and  with  slashes separating the parts of the date;
	      otherwise, times are output 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  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 the revision was checked in.   With  -zzone  a
	      numeric  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 appended 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
	      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
	      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 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,
	      inserted	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:  $.

       $RCSfile$
	      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
       sequences 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	possi-
       ble.   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),
       rcsclean(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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