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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

Buy it now, or read it online on Safari Bookshelf.


kill [options] [pids | commands]

Send a signal to terminate one or more process IDs. You must own the process or be a privileged user. If no signal is specified, TERM is sent.

This entry describes the /bin/kill command, which offers several powerful features. There are also built-in shell commands of the same name; the bash and ksh versions are described in Chapter 6.

In particular, /bin/kill allows you to specify a command name, such as gcc or xpdf, instead of a process ID (PID). All processes running that command with the same UID as the process issuing /bin/kill will be sent the signal.

If /bin/kill is issued with a pid of 0, it sends the signal to all processes of its own process group. If /bin/kill is issued with a pid of -1, it sends the signal to all processes except process 1 (the system's init process).



Kill all processes of the given name (if privileges allow), not just processes with the same UID. To use this option, specify the full path (e.g., /bin/kill -a gcc).


List all signals.


Print the process ID of the named process, but don't send it a signal. To use this option, specify the full path (e.g., /bin/kill -p).


The signal number (from /usr/include/sys/signal.h) or name (from kill -l). With a signal number of 9 (KILL), the kill cannot be caught by the process; use this to kill a process that a plain kill doesn't terminate. The default is TERM. The letter flag itself is optional: both kill -9 1024 and kill -s 9 1024 terminate process 1024.

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