Chaining Commands Together

Command line programs take input, write output and write errors
Done through three "Streams" -- stdin, stdout, stderr
Output and Errors can be sent to other places besides the screen
> redirects output into a file % ls > listing.txt % cat listing.txt PapaRoach--Getting_Away_With_Murder.mp3 NIN--Closer.mp3
| puts output from one program into the input of another % ls | wc 2 2 58
Too much output? Pipe through less or more % ./really_verbose_script | less