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       co - check out RCS revisions


       co [options] file ...


       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 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
       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


              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:
              5.13 $ 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

       -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 example,  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
              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  5.13  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
              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

              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.

       -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 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

              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

              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
              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:

                      * $Log$

              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:  $.

              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
       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.
              See ci(1) for details.


       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.


       Author: Walter F. Tichy.
       Manual Page Revision: 5.13; Release Date: 1995/06/01.
       Copyright © 1982, 1988, 1989 Walter F. Tichy.
       Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.


       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.


       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.