rcsfile(5)
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 (n2) (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: 2015-06-21. 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.
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