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KILL(2)			      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
       specified  in sigaction(2) or it	may be 0, in which case	error checking
       is performed but	no signal is actually sent.  This can be used to check
       the validity of pid.

       For a process to	have permission	to send	a signal to a  process	desig-
       nated  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 always	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 permis-
	       sions 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 correspond-
			  ing 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	13.2		       December	1, 2019			       KILL(2)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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