co

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 cor-
       responding working file.

       Filenames 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-
       low).

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 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
              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:
              5.9.4 $ 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 Re-
              vision keyword, generate the string $Revision$ instead of $Revi-
              sion:  5.9.4 $.  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: 5.9.4 $ 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 5.9.4  instead  of
              $Revision: 5.9.4 $.  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.

       -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  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.

       -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     Enable self-same mode.  In this mode, the owner  of  a  lock  is
              unimportant,  just  that it exists.  Effectively, this means the
              user cannot check out the same revision 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 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.

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 RCS file name,  the  revi-
              sion  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 file name is without the
              directory components.

       $Locker$
              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 file name, 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:
              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,  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:  $.

       $RCSfile$
              The RCS file name without directory components.

       $Revision$
              The revision number assigned to the revision.

       $Source$
              The full RCS file name.

       $State$
              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.  A
              backslash escapes spaces within an option.  The RCSINIT  options
              are  prepended to the argument lists of most RCS commands.  Use-
              ful RCSINIT options include -q, -V, -x, and -z.

       RCS_MEM_LIMIT
              Normally, for speed, commands either memory  map  or  copy  into
              memory  the  RCS file if its size is less than the memory-limit,
              currently defaulting to ``unlimited''.   Otherwise  (or  if  the
              initially-tried speedy ways fail), the commands fall back to us-
              ing standard i/o routines.  You can adjust the memory  limit  by
              setting  RCS_MEM_LIMIT to a numeric value lim (measured in kilo-
              bytes).  An empty value is silently ignored.  As a side  effect,
              specifying RCS_MEM_LIMIT inhibits fall-back to slower routines.

       TMPDIR Name  of  the  temporary directory.  If not set, the environment
              variables TMP and TEMP are inspected instead and the first value
              found  is  taken;  if none of them are set, a host-dependent de-
              fault is used, typically /tmp.

DIAGNOSTICS
       The RCS file name, the working file name, 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.

IDENTIFICATION
       Author: Walter F. Tichy.
       Manual Page Revision: 5.9.4; Release Date: 2019-12-31.
       Copyright (C) 2010-2015 Thien-Thi Nguyen.
       Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
       Copyright (C) 1982, 1988, 1989 Walter F. Tichy.

SEE ALSO
       ci(1), ctime(3), date(1), ident(1), make(1), rcs(1), rcsclean(1), rcsd-
       iff(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.

       The full documentation for RCS is maintained as a Texinfo  manual.   If
       the  info(1)  and RCS programs are properly installed at your site, the
       command

              info rcs

       should give you access to the complete manual.  Additionally,  the  RCS
       homepage:

              http://www.gnu.org/software/rcs/

       has news and links to the latest release, development site, etc.

LIMITS
       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 RCS 5.9.4                     2019-12-31                             CO(1)
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