rcsfile - RCS file format
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 2
n fields
(
n≥2) (e.g., 3.1.1.1, 2.1.2.2, etc.) are linked as follows. All
nodes whose first 2
n-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 2
n-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 /
\ /
\ /
\ /
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.
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.