File names may be specified as the working file name (with an implied
\*S/\fBs.\fPfile), as the \fBs.\fPfile (with an implied \fBg\fPfile of
\fBfile\fP), as nothing (with the implied list being \fB\*S/s.*\fP),
or as a single "\fB-\fP" which means to read the file list from
\fIstdin\fP.
.PP
Unlike in \*(AT, \fBs.\fPfiles cannot be located in the same directory
as their corresponding \fBg\fPfiles; they must be placed in an \*S
subdir.
