Source Code Control System (SCCS)

1
Source Code Control System (SCCS)

• Banyen Sae-Lee
• 4322031

2
Introduction

• Programmers Guide, UNIX System V, ATT, 1987
• Is a maintenance and enhancement tracking tool
  that runs under the UNIX system

• http//nacphy.physics.orst.edu/copying-with-unix/
  node169.html
• The source code control system SCCS is a set of
  commands which helps you keep track of the
  changes made to source code (or any text) files

3
Introduction

• It's like a friendly librarian and accountant for
  your files who even helps you restore your files
  to the condition they were in at some previous
  time. The SCCS is particularly handy when a group
  is making changes to the same source code or a
  single person likes to try out lots of changes
  but keeps forgetting how to get the code back to
  where it runs.

4
Basic Operation

• SCCS stores changes to files in a file that is
  called, logically, An SCCS file.
• The SCCS file is named s.filename, where filename
  is the file being tracked.
• Each set of changes depending on the previous
  revision

5
Basic Operation
This is a simple 3 line file

• SCCS adds only the last line to the SCCS file
  s.filename and records it as the next revision

6
SCCS for Beginners

• Creating an SCCS File via admin
• Retrieving a File via get
• Recording Change via delta

7
Creating an SCCS File via admin

• file1.txt
• This is
• a simple
• 3 line

admin ifile1.txt s.file1.txt
ls l-rw-r--r-- 1 sbanyen ccstaff 24
Feb 16 1317 file1.txt-r--r--r-- 1 sbanyen
ccstaff 178 Feb 16 1317 s.file1.txt

• file1.txt is no longer needed because it exists
  now under SCCS as s.file1.txt
• rm file1.txt

8
Retrieving a File via get

• get s.file1.txt

get e s.file1.txt
1.13 lines No ID keywords (cm7) get retrieved
version 1.1 with three lines of text for reading
1.1new delta 1.23 lines get creates file1.txt
for both reading and writing
9
Recording Change via delta

• delta s.file1.txtcomments? Change 3 to
  threeNo id keywords (cm7)1.21 inserted1
  deleted2 unchanged

10
Delta Numbering

• Think of deltas as the nodes of a tree in which
  the root nodes is the original version of the
  file.
• The root is normally named 1.1 and deltas (nodes)
  are named 1.2, 1.3, etc.
• The components of these SIDs are called release
  and level numbers.

11
Delta Numbering

• This is the normal sequential development of an
  SCCS file, which each delta dependent on the
  preceding deltas.
• Such struture is called the trunk of an SCCS tree.

12
Delta Numbering

• There are situation the require branching an SCCS
  file. That is, changes are planned to a given
  delta that will not be dependent on all previous
  deltas.
• Branch delta names always have fours SID
  components
• release.level.branch.sequence

13
Delta Numbering
14
Delta Numbering
15
SCCS command

• SCCS commands accept two types of arguments
• keyletters
• filenames

16
SCCS command

• admin initializes SCCS files, manipulates their
  descriptive text, and controls delta creation
  rights
• get retrieves versions of SCCS files
• unget undoes the effect of a get -e prior to the
  file being deltaed

17
SCCS command

• delta applies (changes) to SCCS files and creates
  new versions
• prs prints portions of an SCCS file in user
  specified format
• sact print information about the fils that are
  currently out for edit

18
SCCS command

• rmdel removes a delta from an SCCS file allows
  removal of deltas created by mistake
• cdc changes the commentary assocoated with a
  delta
• sccsdif shows differences between any two
  versions of an SCCS file

19
SCCS command

• what searches any UNIX system file(s) for all
  occurences of a special pattern and prints out
  what follows it useful in filnding identifying
  information inserted by the get command
• comb combines consecutive deltas into one to
  reduce the size of an SCCS file
• Other can see in man pages of Unix.

20
The admin Command

• The admin command is used to administer SCCS
  file.When an SCCS file is created, its parameters
  are initialized by use of keyletters with admin
  or are assigned default values if no keyletters
  are supplied.

21
The admin Command

• Initialize the history file with text from the
  indicated file.
• Create the history file called s.program.c in the
  SCCS subdirectory.
• Specify the release for the initial delta.

admin ifile1.txt s.file1.txt create SCCS
file1.txt admin ifile1.txt r3 s.file1.txt
22
The admin Command

• SCCS files contain a list of login names and/or
  group Ids of users who are allowed to create
  deltas.
• This list is empty by default, allowing anyone to
  create deltas.
• To create a user list (or add to an existing
  one), admin -a is used. For example
• admin -assupacho -avpreecha s.file1.txt

23
The get Command

• The get utility retrieves a working copy from the
  SCCS history file, according to the specified
  options.
• The retrieved file normally has the same
  filename base as the s.file, less the
  prefix, and is referred to as the g- file.
• retrieve a version of an SCCS file get
  s.file1.txt

24
The get Command

• ID keywords (Identification keywords)
• In generating a g-file for compilation, it is
  useful to record the date and time of creation,
  the version retrieved, the modules name, etc.
  within the g-file.
• This information appears in a load module when
  one is eventually created.

25
The get Command

• ID keywords (Identification keywords)
• ID keywords appearing anywhere in the generated
  file are replaced by appropriate values according
  to the definitions of those ID keywords

26
The get Command

• ID keywords (Identification keywords)
• The format of an ID keyword is an upper case
  letter emclosed by percent signs, . For example
  I is the ID keyword replaced by the SID of the
  retrieved version of a file.

27
The get Command

• Retrieve the version corresponding to the
  indicated SID (delta). get r s.file1.txt
• Retrieve a version for editing get -e
  s.file1.txt
• Create a new branch. get b e r1.2
  s.file1.txt

28
The get Command

• Retrieval With Intent to Make a Delta get -e
  indicates an intent to make a delta. First, get
  checks the following.
• The user list to determine if the login name or
  group ID of the person executing get is present.
  The login name or group-ID of the person
  executing get must be present for the user to be
  allowed to make deltas.

29
The get Command

• Retrieval With Intent to Make a Delta
• The release number (R) of the version being
  retrieved statisfies the relation floor is
  greater than or equal to R, which is less than or
  equal to ceiling to determine if the release
  being accessed is a protected release. The floor
  and ceiling are flags in the SCCS file
  representing start and end of range.

30
The get Command

• Retrieval With Intent to Make a Delta
• The R is not locked against editing. The lock is
  a flag in the SCCS file.
• Whether multiple concurrent edits are allowed for
  the SCCS file by the j flag in the SCCS file.

31
The get Command

• Retrieval With Intent to Make a Delta
• A failure of any of the first three conditions
  causes the processing of the corresponding SCCS
  file to terminate.
• If the above checks succeed, get -e causes the
  creation of a g-file in the current directory
  with mode 644, owned by the real user.

32
The get Command

• Retrieval With Intent to Make a Delta
• If a writable g-file already exists, get
  terminates with an error.This is prevent
  inadvertent destruction of a g-file being edited
  for the purpose of maling a delta.
• get -e causes the creation (or updating) of a
  p.filename that is used to pass information to
  the delta command.

33
The get Command

• Retrieval With Intent to Make a Delta
• The p.filename prevents other users from
  retrieving the same version for editing until
  this one is checked in using delta or unget.
• Read only copied can be check out.
• Can use the -r option for different versions at
  the same time

34
The get Command

• Retrieval With Intent to Make a Delta
• However, if two users are making changes to the
  same file at the same time, the project most
  likely will have branches in the revision tree.

35
Undoing a get -e

• There may be times when a file is retrieved for
  editing in error there is really no editing that
  needs to be done at this time.In such cases, the
  unget command can be used to cancel the delta
  reservation that was set up.

36
The delta Command

• The delta command is used to incorporate changes
  made to a g-file into the corresponding SCCS file
• The delta command requ ires the existence of a
  p.filename. It examines the p.filename to verify
  the presence of an entry containing the users
  login name. If none is found, an error message
  results.

37
The delta Command

• If all checks are successful, delta determines
  what has been changed in the g-file by comparing
  it via diff (1) with its own temporary copy of
  the g-file as it was before editing.
• If the login name of the user appears in more
  than one entry, Then delta -r must be used to
  specify the SID that uniquely identifies the
  p.filename entry.

38
The delta Command
ls -l total 2 -r--r--r-- 1 sbanyen ccstaff
513 Feb 18 1024 s.file1.txt get -e
s.file1.txt 1.2 new delta 1.3 4 lines
39
The delta Command

• ls -l
• total 6
• -rw-r--r-- 1 sbanyen ccstaff 33 Feb 18
  1024 file1.txt
• -rw-r--r-- 1 sbanyen ccstaff 34 Feb 18
  1024 p.file1.txt
• -r--r--r-- 1 sbanyen ccstaff 513 Feb 18
  1024 s.file1.txt

40
The delta Command

• delta s.file1.txt
• comments? Add comment
• 1.3
• 1 inserted
• 1 deleted
• 3 unchanged

41
The delta Command

• After the processing of an SCCS file is
  complete, the corresponding p.filename emtry is
  removed from the p.filename.
• delta removes the edited g-file unless -n is
  specified. For example
• delta -n s.file1.txt
• will keep the g-file after processing.

42
The prs Command

• The prs command is used to print all or part of
  an SCCS file on the standard output.
• prs s.file1.txt
• D 1.1 01/02/17 204450 sbanyen 1 0
  00003/00000/00000
• MRs
• COMMENTS
• date and time created 01/02/17 204450 by sbanyen

43
The prs Command

• If prs -d is used, the output will be in a format
  called data specification.
• Data specification is a string of SCCS file data
  keywords interspersed with optional user text.
• Data keywords are replaced by appropriate values
  according to their definition

44
The prs Command

• Example
• prs -d "File M version I created D"
  s.file1.txt
• File file1.txt version 1.3 created 01/02/18

45
The sact Command

• sact is like a special form of the prs command
  that produces a report about files that are out
  for edit.The command takes only one type of
  argument a list of file or directory name.
• sact s.file1.txt
• 1.3 1.4 sbanyen 01/02/18 122338

46
The rmdel Command

• The rmdel command allows removal of a delta from
  an SCCS file.
• The delta to be removed must be leaf delta.
• The effective user must have write permission is
  the directory containing the SCCS file.

47
The rmdel Command

• Check the SID to make sure it is not for a
  version on which a get for editing had been
  executed and whose associated delta has not yet
  been made.
• The login name or group ID of the user must
  appear in the files users list ( or the user
  list must be empty).
• Example rmdel -r1.3 s.file1.txt

48
The cdc Command

• The cdc command is used to changed the commentary
  made when the delta was created. It is similar to
  the rmdel command (e.g., -r and full SID are
  necessary) although the delta need not be a leaf
  delta.

For example cdc -r1.2 s.file1.txt comments?
Change number 3 to three word
49
The what Command

• The what command is used to find identifying
  within any UNIX file whose name is given as an
  argument. No keyletters are accepted.
• The what command search the given file(s) for all
  occurences of the string _at_() which is the
  replacement for the Z ID keyword.

50
The what Command

• For example, if an SCCS file called s.file1.txt
  contains the following line Filename is W and
  the command
• get s.file1.txt
• what file1.txt
• file1.txt
• file1.txt 1.3

51
The what Command

• The string searched for by what need not be
  inserted via and ID keyword of get if may be
  inserted in any convenient manner.

52
The sccsdiff Command

• The sccsdiff command determines (and prints on
  the standard output) the differences between any
  two versions of an SCCS file.
• The versions to be compared are specified with
  sccsdiff -r in the same way as with get -r.

53
The sccsdiff Command

• For example
• sccsdiff -r1.2 -r1.3 s.file1.txt
• 1c1
• lt I M
• ---
• gt File name is W

54
The comb Command

• The comb command lets t he user try to reduce the
  size of an SCCS file, restructs the file by
  discarding unwanted deltas and combining other
  specified deltas.
• In the absence of any keyletters, comb preserves
  only leaf deltas and the minimum number of
  ancestor deltas necessary to preserve the shape
  of an SCCS tree.

55
The comb Command

• Deltas 1.2, 1.3.2.1, 1.4 and 2.1 would be
  eliminate

56
Reference

• Karen S. Fortgang , UNIX System V (Programmers
  Guide), Prentice-Hall, Inc., Englewood Cliffs, NJ
  07632, 1987.
• Robin Burk and David B. Horvath, CCP.,et al.,
  UNIX Unreleased Internet Edition, Techmedia
  Monish Plaza, 20, Ansari Road, Darya Ganj, New
  Delhi-2., 1998.
• http//nacphy.physics.orst.edu/copying-with-unix/
  node169.html