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The first program is the
who command. By itself, it generates a
list of the users who are currently logged in. Although I’m writing
this on a single-user system, we’ll pretend that several people are
$ who -| arnold console Jan 22 19:57 -| miriam ttyp0 Jan 23 14:19(:0.0) -| bill ttyp1 Jan 21 09:32(:0.0) -| arnold ttyp2 Jan 23 20:48(:0.0)
Here, the ‘$’ is the usual shell prompt, at which I typed ‘who’.
There are three people logged in, and I am logged in twice. On traditional
Unix systems, user names are never more than eight characters long. This
little bit of trivia will be useful later. The output of
who is nice,
but the data is not all that exciting.