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KILL(2)			    BSD	System Calls Manual		       KILL(2)

NAME
     kill -- send signal to a process

LIBRARY
     Standard C	Library	(libc, -lc)

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

     int
     kill(pid_t	pid, int sig);

DESCRIPTION
     The kill()	system call sends the signal given by sig to pid, a process or
     a group of	processes.  The	sig argument may be one	of the signals speci-
     fied in sigaction(2) or it	may be 0, in which case	error checking is per-
     formed but	no signal is actually sent.  This can be used to check the va-
     lidity of pid.

     For a process to have permission to send a	signal to a process designated
     by	pid, the real or effective user	ID of the receiving process must match
     that of the sending process or the	user must have appropriate privileges
     (such as given by a set-user-ID program or	the user is the	super-user).
     A single exception	is the signal SIGCONT, which may always	be sent	to any
     process with the same session ID as the caller.

     If	pid is greater than zero:
	     The sig signal is sent to the process whose ID is equal to	pid.

     If	pid is zero:
	     The sig signal is sent to all processes whose group ID is equal
	     to	the process group ID of	the sender, and	for which the process
	     has permission; this is a variant of killpg(2).

     If	pid is -1:
	     If	the user has super-user	privileges, the	signal is sent to all
	     processes excluding system	processes (with	P_SYSTEM flag set),
	     process with ID 1 (usually	init(8)), and the process sending the
	     signal.  If the user is not the super user, the signal is sent to
	     all processes with	the same uid as	the user excluding the process
	     sending the signal.  No error is returned if any process could be
	     signaled.

     For compatibility with System V, if the process number is negative	but
     not -1, the signal	is sent	to all processes whose process group ID	is
     equal to the absolute value of the	process	number.	 This is a variant of
     killpg(2).

RETURN VALUES
     The kill()	function returns the value 0 if	successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The kill()	system call will fail and no signal will be sent if:

     [EINVAL]		The sig	argument is not	a valid	signal number.

     [ESRCH]		No process can be found	corresponding to that speci-
			fied by	pid.

     [ESRCH]		The process id was given as 0 but the sending process
			does not have a	process	group.

     [EPERM]		The sending process is not the super-user and its ef-
			fective	user id	does not match the effective user-id
			of the receiving process.  When	signaling a process
			group, this error is returned if any members of	the
			group could not	be signaled.

SEE ALSO
     getpgrp(2), getpid(2), killpg(2), sigaction(2), raise(3), init(8)

STANDARDS
     The kill()	system call is expected	to conform to ISO/IEC 9945-1:1990
     ("POSIX.1").

HISTORY
     The kill()	function appeared in Version 7 AT&T UNIX.

BSD				April 19, 1994				   BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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