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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 corresponding 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.   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 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 restric-
       tions, 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  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 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 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 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 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 exam-
              ple, 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 can-
              not 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, 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 sub-
              stitution 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 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) 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 joinlist.  This option is largely obso-
              leted 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)  revision  numbers.   For  the initial such pair, rev1 denotes the revision 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 correspondents are run-
              ning, 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 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 con-
              tain different white space and line prefixes in the substitution 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 check-
       out.  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; oth-
              erwise, 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;  other-
              wise,  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 obso-
              lescent 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 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),  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)