SCCS commands accept two types of arguments:
File arguments, which may be file or directory names, specify the file(s) that the SCCS command is to process. Naming a directory is equivalent to naming all the SCCS files contained in the directory, in which case non-SCCS files and files which are unreadable are silently ignored.
In general, a filename argument may not begin with a minus sign. If a filename - (a single minus sign) is specified, the command reads the standard input (usually your terminal) for lines and takes 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 with, for example, the commands find(C) and ls(C).
Key letters are processed before filenames. Therefore, the placement of key letters is arbitrary; that is, they may be interspersed with file names. File names, however, are processed left to right. Somewhat different conventions apply to what(CP), sccsdiff(CP), and val(CP), detailed later under SCCS commands and documented in their respective manual pages.
Certain actions of various SCCS commands are controlled by flags appearing in SCCS files. Some of these flags are discussed, but for a complete description see admin(CP).
There is distinction between real user and effective user when discussing various actions of SCCS commands. For now, assume that the person logged into the UNIX system is both the real and effective user. See passwd(C) for more about real and effective users.