KILL

kill ? send signal to a process

#include <sys/types.h>
#include <signal.h>

int kill(pid_t pid, int sig);

The kill system call can be used to send any signal to any process group or process.

If pid is positive, then signal sig is sent to pid.

If pid equals 0, then sig is sent to every process in the process group of the current process.

If pid equals ?1, then sig is sent to every process except for the first one, from higher numbers in the process table to lower.

If pid is less than ?1, then sig is sent to every process in the process group ?pid.

If sig is 0, then no signal is sent, but error checking is still performed.

On success, zero is returned. On error, ?1 is returned, and errno is set appropriately.

EINVAL

An invalid signal was specified.

ESRCH

The pid or process group does not exist. Note that an existing process might be a zombie, a process which already committed termination, but has not yet been wait()ed for.

EPERM

The process does not have permission to send the signal to any of the receiving processes. For a process to have permission to send a signal to process pid it must either have root privileges, or the real or effective user ID of the sending process must equal the real or saved set-user-ID of the receiving process.

It is impossible to send a signal to task number one, the init process, for which it has not installed a signal handler. This is done to assure the system is not brought down accidentally.

SVr4, SVID, POSIX.1, X/OPEN, BSD 4.3

_exit(2), exit(3), signal(2), signal(7)