College of Engineering & CS Wright State University Dayton, Ohio 45435-0001

CEG 333: Introduction to Unix Prabhaker Mateti kill

Syntax: kill -[SIGNAL] PID...

Despite its name, ending processes is only one function of the kill command. More generally, it sends signals to processes (i.e., it raises exceptions). Programs can either catch these signals and handle them gracefully, or allow the operating system default to handle them.

The default signal sent by kill is SIGTERM. A different signal can be given before the PIDs, either by number (kill -1) or by name (with or without the "SIG", kill -HUP and kill -SIGHUP both work).

Signals are sent for other events besides the user running kill. Many of the most common signals are never sent directly by users except when testing. Bugs in a program may cause it to terminate with SIGSEGV, and pressing control-c usually sends SIGINT, for example.

WARNING: signal numbers may vary between Unix flavors. The most common signals usually stay the same, but it's a good idea to check kill -l for supported signals. Further, although many systems provide convenience utilities for common tasks, they sometimes have different effects when moving between systems. For example, the same command that kills all processes matching a certain name on Linux will end all running processes on Solaris!

Common Signals: