Name

sccsfile − format of SCCS file

Description

An SCCS file is an ASCII file that consists of six logical parts.  These six parts include checksum, delta table (contains information about each delta), user names (contains login names and/or numerical group IDs of users who may add deltas), flags (contains definitions of internal keywords), comments (contains arbitrary descriptive information about the file), and body (contains the actual text lines intermixed with control lines). 

Throughout an SCCS file there are lines that begin with the ASCII SOH (start of heading) character (octal 001).  This character is hereafter referred to as the control character and will be represented graphically as @.  Any line described that is not shown beginning with the control character is prevented from beginning with the control character. 

Entries of the form DDDDD represent a 5-digit string number between 00000 and 99999.

The logical parts of an SCCS file, described in detail, are:

Checksum
The checksum is the first line of an SCCS file. The form of the line is:

@hDDDDD

The value of the checksum is the sum of all characters, except those of the first line.  The @h provides a magic number of (octal) 064001. 

Delta table
The delta table consists of a variable number of entries of the form:

@s DDDDD/DDDDD/DDDDD
@d <type> <SCCS ID> yr/mo/da hr:mi:se <pgmr> DDDDD DDDDD
@i DDDDD ...
@x DDDDD ...
@g DDDDD ...
@m <MR number>
  .
  .
  .
@c <comment> ...
  .
  .
  .
@e

The first line (@s) contains the number of lines inserted/deleted/unchanged, respectively. The second line (@d) contains the type of the delta (normal: D and removed: R), the SCCS ID of the delta, the date and time of creation of the delta, the login name corresponding to the real user ID at the time the delta was created, and the serial numbers of the delta and its predecessor, respectively. The @i, @x, and @g lines contain the serial numbers of deltas included, excluded, and ignored, respectively. These lines are optional. The @m lines (optional) each contain one MR number associated with the delta. The @c lines contain comments associated with the delta.

The @e line ends the delta table entry.

User names
The list of login names and numerical group ID of users who may add deltas to the file, separated by newlines. The lines containing these login names and numerical group ID are surrounded by the bracketing lines @u and @U. An empty list allows anyone to make a delta.

Flags Keywords used internally.  See admin() for more information on their use. Each flag line takes the form: @f <flag><optional text>
The following flags are defined:

@f t<type of program>
@f v<program name>
@f i
@f b
@f m<module name>
@f f<floor>
@f c<ceiling>
@f d<default-sid>
@f n
@f j
@f l<lock-releases>
@f q<user defined>
@f z<reserved for use in interfaces>

The t flag defines the replacement for the ­%Y­% identification keyword.

The v flag controls prompting for MR numbers, in addition to comments. If the optional text is present, it defines an MR number-validity checking program.

The i flag controls the warning/error aspect of the “No id keywords” message. When the i flag is not present, this message is only a warning; when the i flag is present, this message will cause a fatal error (the file will not be retrieved or the delta will not be made).

When the b flag is present, the −b option can be specified with the get command to cause a branch in the delta tree.

The m flag defines the first choice for the replacement text of the ­%M­% identification keyword.

The f flag defines the “floor” release: the release below which no deltas may be added.

The c flag defines the “ceiling” release: the release above which no deltas may be added.

The d flag defines the default SID to be used when none is specified on a get command.

The n flag causes delta to insert a null delta (a delta that applies no changes) in those releases that are skipped when a delta is made in a new release. For example, when delta 5.1 is made after delta 2.7, releases 3 and 4 are skipped.  The absence of the n flag causes skipped releases to be completely empty.

The j flag causes get to allow concurrent edits of the same base I.

The l flag defines a list of releases that are locked against editing get with the −e option.

The q flag defines the replacement for the ­%Q­% identification keyword.

The z flag is used in certain specialized interface programs.

Comments
Arbitrary text surrounded by the bracketing lines @t and @T. The comments section typically contains a description of the file’s purpose.

Body    
The body consists of text lines and control lines. Text lines do not begin with the control character; control lines do. There are three kinds of control lines: insert, delete, and end, represented by the following:

@I DDDDD
@D DDDDD
@E DDDDD

The digit string is the serial number corresponding to the delta for the control line. 

See Also

(1), delta(1), get(1), prs(1), sccs(1)
An Introduction to the Source Code
Eric Allman, Supplementary Documentation, Vol. II.