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CO(1)                       General Commands Manual                      CO(1)

       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 access list 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:
              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 " * "
              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 (C) 1982, 1988, 1989 Walter F. Tichy.
       Copyright (C) 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.

GNU                               1995/06/01                             CO(1)