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RCSFILE(5)                    File Formats Manual                   RCSFILE(5)



NAME
       rcsfile - format of RCS file

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 carriage 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;
       Terminal 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  ;}
                 { comment {string}; }
                 { expand  {string}; }
                 { newphrase }*

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

       desc ::=  desc string

       deltatext ::=  num
                 log  string
                 { newphrase }*
                 text string

       num  ::=  {digit | .}+

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

       id   ::=  {num} idchar {idchar | num}*

       sym  ::=  {digit}* idchar {idchar | digit}*

       idchar    ::=  any visible graphic character except special

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

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

       newphrase ::=  id word* ;

       word ::=  id | num | string | :

       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 newphrase productions in the grammar are reserved for future
       extensions to the format of RCS files.  No newphrase will begin with
       any keyword already in use.

       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 decreasing 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.

IDENTIFICATION
       Author: Walter F. Tichy, Purdue University, West Lafayette, IN, 47907.
       Manual Page Revision: ; Release Date: .
       Copyright (C) 1982, 1988, 1989 Walter F. Tichy.
       Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.

SEE ALSO
       rcsintro(1), 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.



                                      GNU                           RCSFILE(5)