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7.1 Child Processes

Unlike some other implementations of sccs, cssc tools do not usually execute each other. This means for example that delta does not invoke get to extract the previous version of the file, and prs doesn't use get when processing the :GB: keyword.

There are a small number of exceptions to this rule :-

The sccs driver program can be used to invoke any of the other tools in the suite. See Known Problems, for a discussion of the issues this raises.
The delta program runs a program to validate the Modification Request Numbers offered by the user. See Modification Request Numbers.
The sccsdiff program is a shell script, and invokes get, diff and pr, as well as other tools such as cat, test and rm. The sccsdiff program must not be installed set-user-id.

The driver program sccs takes a number of precautionary steps if it detects that it is running set-user-id or set-group-id. These steps are described below, as part of the discussion of each environment variable.