Processes

• A process is a running instantiation of a program

• It includes the program's object code

• But also a bunch of other information

• You probably have only one program for cat.

• /bin/cat perhaps

• But there might be many cat processes at any time

        % cat -n foo bar baz | cat header - footer

        % psgrep cat
        USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
        zostay     119  0.0  0.0   7180   356 pts/4    R    15:10   0:00 cat seek1.pic seek2.pic ...
        awillis   4926  0.0  0.0   7180   356 pts/8    R    12:23   0:00 cat
        mjd      11332  0.0  0.0   7180   356 pts/0    T    15:17   0:00 cat
        waltman  23981  0.0  0.0   7180   356 ?        R    15:17   0:00 cat bigfile
        gavery   28317  0.0  0.0   7180   356 pts/1    R    15:10   0:00 cat

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