The concept of a terminal comes
from the old days, when people worked exclusively from character terminals, so a terminal typi-
NOTE
NOTE
43
Running Commands from the Shell 2
cally represented a single person at a single screen. Now you can have many ???terminals??? on one
screen by opening multiple Terminal windows.
On this shell session, there isn??™t much happening. The first process shows that the user named
jake logged in to the login process (which is controlled by the root user). The next process shows
that jake is using a bash shell and has just run the ps au command. The terminal device ttyp0
is being used for the login session. The STAT column represents the state of the process, with R
indicating a currently running process and S representing a sleeping process.
Several other values can appear under the STAT column. For example, a plus sign (+)
indicates that the process is associated with the foreground operations.
The USER column shows the name of the user who started the process. Each process is represented
by a unique ID number referred to as a process ID (PID). (You can use the PID if you ever need to
kill a runaway process.) The %CPU and %MEM columns show the percentages of the processor and
random access memory, respectively, that the process is consuming.
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