HP UX Operating Systems 419

kill(1)			kill(1)
24	SIGSTOP	Stop	Pause the process; cannot be trapped
25	SIGTSTP	Terminal stop	Pause the process; can be trapped
26	SIGCONT	Continue	Run a stopped process

SIGNULL (0), the null signal, invokes error checking but no signal is actually sent. This can be used to test the validity or existence of pid.

SIGTERM (15), the (default) terminate signal, can be trapped by the receiving process, allowing the receiver to execute an orderly shutdown or to ignore the signal entirely. For orderly operations, this is the perferred choice.

SIGKILL (9), the kill signal, forces a process to terminate immediately. Since SIGKILL cannot be trapped or ignored, it is useful for terminating a process that does not respond to SIGTERM.

The receiving process must belong to the user of the sending process, unless the user has appropriate privileges.

As a single special case, the continue signal SIGCONT can be sent to any process that is a member of the same session as the sending process.

RETURN VALUE

Upon completion, kill returns with one of the following values:

0At least one matching process was found for each pid operand, and the speci®ed signal was suc- cessfully processed for at least one matching process.

>0 An error occurred.

EXAMPLES

The command:

kill 6135

signals process number 6135 to terminate. This gives the process an opportunity to exit gracefully (remov- ing temporary ®les, etc.).

The following equivalent commands:

kill -s SIGKILL 6135 kill -s KILL 6135 kill -s 9 6135 kill -SIGKILL 6135 kill -KILL 6135 kill -9 6135

terminate process number 6135 abruptly by sending a SIGKILL signal to the process. This tells the kernel to remove the process immediately.

WARNINGS

If a process hangs during some operation (such as I/O) so that it is never scheduled, it cannot die until it is allowed to run. Thus, such a process may never go away after the kill. Similarly, defunct processes (see ps(1)) may have already ®nished executing, but remain on the system until their parent reaps them (see wait(2)). Using kill to send signals to them has no effect.

Some non-HP-UXimplementations provide kill only as a shell built-in command.

DEPENDENCIES

This manual entry describes the external command /usr/bin/kill and the built-in kill command of the POSIX shell (see sh-posix(1)). Other shells, such as C and Korn (see csh(1) and ksh(1) respectively), also provide kill as a built-in command. The syntax for and output from these built-ins may be different.