Provided by: rcs_5.9.4-6_amd64 
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
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 ;}
{ 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 interoperate 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
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.
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: 5.9.4; Release Date: 2019-12-31.
Copyright © 2010-2015 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.