Provided by: rcs_5.10.1-1_amd64 bug


       co - check out RCS revisions


       co [options] file ...


       co  retrieves  a  revision from each RCS file and stores it into the corresponding working

       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.  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 restrictions, and is not affected by the presence  of

       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).


              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).

              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: 5.10.1 $ 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:  5.10.1  $.   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 $Revision: 5.10.1 $ 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, 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 5.10.1 instead of $Revision: 5.10.1 $.  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.

              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
              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.

              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.

       -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

       -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.

              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

              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 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 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 substitution 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  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.


       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 UTC.

              A  standard header containing the full RCS file name, 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  file  name  is  without  the directory

              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 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: $”, 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 “  ” prefix inside a
              multiline  comment.   For  example,  the  initial  log  comment  of  a  C   program
              conventionally is of the following form:


              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:  $.

              The RCS file name without directory components.

              The revision number assigned to the revision.

              The full RCS file name.

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

              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
              using  standard  i/o  routines.   You  can  adjust  the  memory  limit  by  setting
              RCS_MEM_LIMIT to a numeric value lim (measured in kilobytes).  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 default is used, typically /tmp.


       The RCS file name, the working file name, and the revision number retrieved are written to
       the  diagnostic  output.   The  exit  status  is  zero  if and only if all operations were


       Author: Walter F. Tichy.
       Manual Page Revision: 5.10.1; Release Date: 2022-02-19.
       Copyright © 2010-2022 Thien-Thi Nguyen.
       Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
       Copyright © 1982, 1988, 1989 Walter F. Tichy.


       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.

       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:


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


       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