General Purpose PostScript Generating Utility
10.2.2 How Can I Print
a2ps prints the standard input if you give no file name, or if you gave
`-' as file name. Automatic style selection is of course much
weaker: without the file name, a2ps can only get
opinion (see section 5.4 Style Sheet Files). In general it means most
delegations are safe, but there will probably be no pretty-printing.
`You' can supply a name to the standard input
(`--stdin=name') with which it could guess the language.