SCCS commands accept two types of arguments, keyletters and file names. Keyletters are options that begin with a hyphen (-) followed by a lowercase letter and, in some cases, a value.
File and/or directory names specify the file(s) the command is to process. Naming a directory is equivalent to naming all the SCCS files within the directory. Non-SCCS files and unreadable files in the named directories are silently ignored.
In general, file name arguments may not begin with a hyphen. If a lone hyphen is specified, the command will read the standard input (usually your terminal) for lines and take each line as the name of an SCCS file to be processed. The standard input is read until end-of-file. This feature is often used in pipelines.
Keyletters are processed before file names, so the placement of keyletters is arbitrary--they may be interspersed with file names. File names, however, are processed left to right. Somewhat different conventions apply to help, what, sccsdiff, and val, detailed under ``SCCS commands''.
Certain actions of various SCCS commands are controlled by flags appearing in SCCS files. Some of these flags will be discussed, but for a complete description see admin(1).
The distinction between real user (see passwd(1)) and effective user will be of concern in discussing various actions of SCCS commands. For now, assume that the real and effective users are the same--the person logged into the UNIX system.