Pipes

Pipes connect the standard output of one program to the standard input of another. To do this, just type the two commands with a "|" (vertical bar) between them.

Let's say that you want to see if your friend, John Smith, is logged in, but you don't want to look through all the output from "who". You can take the output from "who" and pipe it through "grep" like this:

["grep" is one in a family of programs that search through a file (or other input) to find a matching pattern. Type "man grep" for more details.]

If he is logged in, you will get something like this:

jsmith ttyqo Jan 29 13:12 If he is not, you won't get any output.

Quite often it is useful to pipe the output from a different program to the "more" program. This will show you the output a page at a time.

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