There are currently two programs available at SAIL for sorting text files.
The more general program is SSORT; for details, READ SSORT.  However, SSORT
takes forever on large, randomly-ordered files.  If you want to sort such a
file, taking each line as a separate record, and do not mind having upper-
and lower-case letters sort separately, you should use MSORT, documented via
READ MSORT.