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1992-02-19
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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, an RCS file must end in a newline character.
Strings are enclosed by @. If a string contains a @, it
must be doubled; otherwise, strings may contain arbitrary
binary data.
The meta syntax uses the following conventions: `|' (bar)
separates alternatives; `{' and `}' enclose optional
phrases; `{' and `}*' enclose phrases that may be repeated
zero or more times; `{' and '}+' enclose phrases that must
appear at least once and may 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 {id : 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 | ... | 9
id ::= letter{idchar}*
letter ::= any letter
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 may overlap. In
most environments RCS uses the ISO 8859/1 encoding: letters
are octal codes 101-132, 141-172, 300-326, 330-366 and 370-
377, visible graphic characters are codes 041-176 and
240-377, and white space characters are codes 010-015 and
040.
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.
Example:
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 /
\ /
\ /
\ /
Fig. 1: A revision tree
IDENTIFICATION
Author: Walter F. Tichy, Purdue University, West Lafayette,
IN, 47907.
Revision Number: 5.2; Release Date: 1992/02/17.
Copyright 1982, 1988, 1989 by Walter F. Tichy.
Copyright 1990, 1991, 1992 by Paul Eggert.
SEE ALSO
ci(1), co(1), ident(1), rcs(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.