38 Welcome, New User!
Most of you, of course, don’t use Unix, so knowing how to kill a job
may not be useful. However, some of you, like me, may have
occasion to run TeX jobs on it periodically, in which case knowing
how to kill jobs is vital. In any case, the design principles underlying
the “kill” command are applied rigorously throughout Unix, so this
message may be more generally useful.Unix lets you suspend a job with ^Z, or quit and kill with ^C. LaTeX
traps ^C, however. Consequently, I used to pile up a few dozen
LaTeX jobs. This didn’t really bother me, but I thought it would be
neighborly to figure out how to get rid of them.Most operating systems have a “kill” command. So does Unix. In
most operating systems, the kill command kills a process. The Unix
implementation is much more general: the “kill” command sends a
process a message. This illustrates the first Unix design principle:- Give the user power by making operations fully general.
The kill command is very powerful; it lets you send all sorts of mes-
sages to processes. For example, one message you can send to a pro-
cess tells it to kill itself. This message is -9. -9 is, of course, the
largest single-digit message, which illustrates another important
Unix design principle:- Choose simple names that reflect function.
In all other operating systems I know of, the kill command without
an argument kills the current job. However, the Unix kill command
always requires a job argument. This wise design choice illustrates
another wise design principle:- Prevent the user from accidentally screwing himself by requiring
long commands or confirmation for dangerous operations.
The applications of this principle in Unix are legion and well docu-
mented, so I need not go into them here, other than perhaps to allude
in passing to the Unix implementations of logging out and of file
deletion.In all other operating systems I know of, the job argument to the kill
command is the name of the job. This is an inadequate interface,
because you may have several LaTeX jobs (for instance) all of which