*nix command to send files to the printer. To send standard input, specify - as one of the files.

lp (options) (files)

Options - there are lots and lots of these, read the man page by typing man lp
Examples
Send mail after printing five copies of star trek jokes: lp -n 5 -m star \trek \jokes
Format and print diaryfile; print title too: nroff -ms diaryfile | lp - title