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rcsfile(5)
NAME DESCRIPTION IDENTIFICATION SEE ALSO
RCSFILE(5)                               File Formats Manual                              RCSFILE(5)



NAME
       rcsfile - RCS file format

DESCRIPTION
       An RCS file's contents are described by the grammar below.

       The  text  is  free format: space, backspace, tab, newline, vertical tab, form feed, and car‐
       riage return (collectively, white space) have no significance except  in  strings.   However,
       white space cannot appear within an id, num, or sym, and an RCS file must end with a newline.

       Strings  are enclosed by @.  If a string contains a @, it must be doubled; otherwise, strings
       can contain arbitrary binary data.

       The meta syntax uses the following conventions: `|' (bar) separates alternatives; `{' and `}'
       enclose  optional  phrases;  `{'  and  `}*' enclose phrases that can be repeated zero or more
       times; `{' and '}+' enclose phrases that must appear at least once and can be repeated;  Ter‐
       minal symbols are in boldface; nonterminal symbols are in italics.

       rcstext   ::=  admin {delta}* desc {deltatext}*

       admin     ::=  head       {num};
                      { branch   {num}; }
                      access     {id}*;
                      symbols    {sym : num}*;
                      locks      {id : num}*;  {strict  ;}
                      { integrity{intstring}; }
                      { comment  {string}; }
                      { expand   {string}; }

       delta     ::=  num
                      date       num;
                      author     id;
                      state      {id};
                      branches   {num}*;
                      next       {num};
                      { commitid sym; }

       desc      ::=  desc       string

       deltatext ::=  num
                      log        string
                      text       string

       num       ::=  {digit | .}+

       digit     ::=  0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

       id        ::=  {idchar | .}+

       sym       ::=  {idchar}+

       idchar    ::=  any visible graphic character except special

       special   ::=  $ | , | . | : | ; | @

       string    ::=  @{any character, with @ doubled}*@

       word      ::=  id | num | string | :

       intchar   ::=  any character, except @

       thirdp    ::=  ^L {intchar}*

       intstring ::=  @ {intchar}* {thirdp}* @

       In releases prior to 5.8 (2011-08-30), the grammar included the newphrase production and used
       it in the admin, delta and deltatext productions.  This allowed third-party programs  to  in‐
       teroperate  with  RCS by storing opaque (to RCS) data in the file.  As of 5.8, in the name of
       progress (towards more systematic file integrity support), the only area reserved for  third-
       party  interop  is in the (string) value of the integrity field, specifically after the first
       ^L (formfeed).  A further restriction (for all programs) is that the integrity value must not
       contain @.

       Identifiers  are  case sensitive.  Keywords are in lower case only.  The sets of keywords and
       identifiers can overlap.  In most environments RCS uses  the  ISO  8859/1  encoding:  visible
       graphic  characters  are  codes  041-176  and  240-377,  and white space characters are codes
       010-015 and 040.

       Dates, which appear after the date keyword, are of the form Y.mm.dd.hh.mm.ss, where Y is  the
       year,  mm  the month (01-12), dd the day (01-31), hh the hour (00-23), mm the minute (00-59),
       and ss the second (00-60).  Y contains just the last two digits of the year  for  years  from
       1900 through 1999, and all the digits of years thereafter.  Dates use the Gregorian calendar;
       times use UTC.

       The delta nodes form a tree.  All nodes whose numbers consist of a single  pair  (e.g.,  2.3,
       2.1, 1.3, etc.)  are on the trunk, and are linked through the next field in order of decreas‐
       ing numbers.  The head field in the admin node points to the head  of  that  sequence  (i.e.,
       contains  the  highest pair).  The branch node in the admin node indicates the default branch
       (or revision) for most RCS operations.  If empty, the default branch is the highest branch on
       the trunk.

       All  delta nodes whose numbers consist of 2n fields (n≥2) (e.g., 3.1.1.1, 2.1.2.2, etc.)  are
       linked as follows.  All nodes whose first 2n-1 number fields are identical are linked through
       the  next field in order of increasing numbers.  For each such sequence, the delta node whose
       number is identical to the first 2n-2 number fields of the deltas on that sequence is  called
       the  branchpoint.   The  branches field of a node contains a list of the numbers of the first
       nodes of all sequences for which it is a branchpoint.  This list  is  ordered  in  increasing
       numbers.

       The following diagram shows an example of an RCS file's organization.

                                  Head
                                    |
                                    |
                                    v                        / \
                                ---------                   /   \
          / \          / \      |       |      / \         /     \
         /   \        /   \     |  2.1  |     /   \       /       \
        /     \      /     \    |       |    /     \     /         \
       /1.2.1.3\    /1.3.1.1\   |       |   /1.2.2.2\   /1.2.2.1.1.1\
       ---------    ---------   ---------   ---------   -------------
           ^            ^           |           ^             ^
           |            |           |           |             |
           |            |           v           |             |
          / \           |       ---------      / \            |
         /   \          |       \  1.3  /     /   \           |
        /     \         ---------\     /     /     \-----------
       /1.2.1.1\      1.3.1       \   /     /1.2.2.1\     1.2.2.1.1
       ---------                   \ /      ---------
           ^                        |           ^
           |                        |           |
           |                        v           |
           |                    ---------       |
           |                    \  1.2  /       |
           ----------------------\     /---------
         1.2.1                    \   /       1.2.2
                                   \ /
                                    |
                                    |
                                    v
                                ---------
                                \  1.1  /
                                 \     /
                                  \   /
                                   \ /


IDENTIFICATION
       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.

SEE ALSO
       ci(1), co(1), ident(1), rcs(1), rcsclean(1), rcsdiff(1), rcsmerge(1), rlog(1).

       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.



GNU RCS 5.10.1                               2022-02-19                                   RCSFILE(5)

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