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Programming Utilities Guide

Checking Files In and Out

The following subcommands are useful when retrieving versions or checking in changes.

Checking Out a File for Editing: sccs edit

To edit a source file, you must check it out first using sccs edit. (The sccs edit command is equivalent to using the -c option to sccs get.)

SCCS responds with the delta ID of the version just retrieved, and the delta ID it assigna when you check in your changes. 

$ sccs edit program.c
1.1
new delta 1.2
87

You can then edit it using a text editor. If a writable copy of the file is present, sccs edit issues an error message; it does not overwrite the file if anyone has write access to it.

Checking in a New Version: sccs delta

Having first checked out your file and completed your edits, you can check in the changes using sccs delta.

Checking a file in is also referred to as making a delta. Before checking in your updates, SCCS prompts you for comments. These typically include a brief summary of your changes. 

$ sccs delta program.c
comments?

Comments should be meaningful, since you may return to the file one day.

You can extend the comment to an additional input line by preceding the NEWLINE with a backslash:

$ sccs delta program.c
comments? corrected typo in widget(), \ 
null pointer in n_crunch()
1.2
5 inserted 
3 deleted
84 unchanged

SCCS responds by noting the SID of the new version, and the numbers of lines inserted, deleted and unchanged. Changed lines count as lines deleted and inserted. SCCS removes the working copy. You can retrieve a read-only version using sccs get.

Think ahead before checking in a version. Creating deltas after each minor edit can become excessive. On the other hand, leaving files checked out for so long that you forget about them can inconvenience others.

It is important to check in all changed files before compiling or installing a module for general use. A good technique is to:

Retrieving a Version: sccs get

To get the most recent version of a file, use the command: 

sccs get filename

For example: 

$ sccs get program.c
1.2
86

retrieves program.c, and reports the version number and the number of lines retrieved. The retrieved copy of program.c has permissions set to read-only.

Do not change this copy of the file, since SCCS does not create a new delta unless the file has been checked out. If you force changes into the retrieved copy, you may lose them the next time someone performs an sccs get or an sccs edit on the file.

Reviewing Pending Changes: sccs diffs

Changes made to a checked-out version, which are not yet checked in, are said to be pending. When editing a file, you can find out what your pending changes are using sccs diffs. The diffs subcommand uses diff(1) to compare your working copy with the most recently checked-in version. 

$ sccs diffs program.c
------ program.c ------ 
37c37 
<		      if (((cmd_p - cmd) + 1) == l_lim) { 
--- 
>	      	if (((cmd_p - cmd) - 1) == l_lim) {

Most of the options to diff can be used. To invoke the -c option to diff, use the -C argument to sccs diffs.

Deleting Pending Changes: sccs unedit

sccs unedit backs out pending changes. This comes in handy if you damage the file while editing it and want to start over. unedit removes the checked-out version, unlocks the history file, and retrieves a read-only copy of the most recent version checked in. After using unedit, it is as if you had not checked out the file at all. To resume editing, use sccs edit to check the file out again. (See also "Repairing a Writable Copy: sccs get -k -G ".)

Combining delta and get: sccs delget

sccs delget combines the actions of delta and get. It checks in your changes and then retrieves a read-only copy of the new version. However, if SCCS encounters an error during the delta, it does not perform the get. When processing a list of file names, delget applies all the deltas it can, and if errors occur, omits all of the get actions.

Combining delta and edit: sccs deledit

sccs deledit performs a delta followed by an edit. You can use this to check in a version and immediately resume editing.

Retrieving a Version by SID: sccs get -r

The -r option allows you to specify the SID to retrieve: 

$ sccs get -r1.1 program.c
1.1
87

Retrieving a Version by Date and Time: sccs get -c

In some cases, you do not know the SID of the delta you want, but you do know the date on (or before) it was checked in. You can retrieve the latest version checked in before a given date and time using the -c option and a date-time argument of the form: 

-cyy [mm [dd [hh [mm [ss ]]]]]

For example: 

$ sccs get -c880722120000 program.c
1.2
86

retrieves whatever version was current as of July 22, 1988 at 12:00 noon. Trailing fields can be omitted (defaulting to their highest legal value), and punctuation can be inserted in the obvious places; for example, the above line could be written as: 

sccs get -c"88/07/22 12:00:00" program.c
Note -

Year 2000 issue. SCCS continues to use a two-digit year representation in the date format. Sun has adopted the proposed specification (XCU5) from the X/Open group that states that values of "yy" from 69 through 99 are to be interpreted as 1969 through 1999 respectively, and values of "yy" from 00 through 68 are to be interpreted as 2000 through 2068 respectively.

Repairing a Writable Copy: sccs get -k -G

Without checking out a new version, sccs get -k -Gfilename retrieves a writable copy of the text, and places it in the file specified by `-G'. This can be useful when you want to replace or repair a damaged working copy using diff and your editor.