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KILL(2)			  FreeBSD 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 user must be the super-user, or the real or saved user	ID of
     the receiving process must	match the real or effective user ID of the
     sending process.  A single	exception is the signal	SIGCONT, which may al-
     ways be sent to any process with the same session ID as the sender.  In
     addition, if the security.bsd.conservative_signals	sysctl(9) is set to 1,
     the user is not a super-user, and the receiver is set-uid,	then only job
     control and terminal control signals may be sent (in particular, only
     SIGKILL, SIGINT, SIGTERM, SIGALRM,	SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP,
     SIGHUP, SIGUSR1, SIGUSR2).

     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 which the caller has	permissions to,	excluding the
	     process sending the signal.  No error is returned if any process
	     could be signaled.

     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 or process group can	be found corresponding
			to that	specified by pid.

     [EPERM]		The sending process does not have permission to	send
			sig to any receiving process.

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

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

HISTORY
     A version of the kill() function appeared in Version 3 AT&T UNIX.	The
     signal number was added to	the kill() function in Version 4 AT&T UNIX.

FreeBSD	13.0		       December	1, 2019			  FreeBSD 13.0
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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