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 sig-
       nificance 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  dou-
       bled; 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 exten-
       sions  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 sin-
       gle  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 num-
       bers.

       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\		  \   /	    /1.2.2.1\
       ---------		   \ /	    ---------
	   ^			    |		^
	   |			    |		|
	   |			    v		|
	   |			---------	|
	   |			\  1.2	/	|
	   ----------------------\     /---------
				  \   /
				   \ /
				    |
				    |
				    v
				---------
				\  1.1	/
				 \     /
				  \   /
				   \ /


IDENTIFICATION
       Author: Walter F. Tichy, Purdue University, West Lafayette, IN, 47907.
       Manual Page Revision: 5.6; Release Date: 1995/06/05.
       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				  1995/06/05			    RCSFILE(5)