KILL(2)								       KILL(2)

NAME    [Toc]    [Back]

     kill - send a signal to a process or a group of processes

C SYNOPSIS    [Toc]    [Back]

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

     int kill (pid_t pid, int sig);

DESCRIPTION    [Toc]    [Back]

     kill sends	a signal to a process or a group of processes.	The process or
     group of processes	to which the signal is to be sent is specified by pid.
     The signal	that is	to be sent is specified	by sig and is either one from
     the list given in signal(2), or 0.	 If sig	is 0 (the null signal),	error
     checking is performed but no signal is actually sent.  This can be	used
     to	check the validity of pid.

     The real or effective user	ID of the sending process must match the real,
     saved,  or	effective user ID of the receiving process, unless the
     effective user ID of the sending process is super-user.  An exception to
     this is the signal	SIGCONT, which may be sent to any descendant, or any
     process in	the same session (having the same session ID) as the current
     process.

     The processes with	a process ID of	0 and a	process	ID of 1	are special
     processes [see intro(2)] and will be referred to below as proc0 and
     proc1, respectively.

     If	pid is greater than zero, sig will be sent to the process whose
     process ID	is equal to pid.  Pid may equal	1.

     If	pid is 0, sig will be sent to all processes excluding proc0 and	proc1
     whose process group ID is equal to	the process group ID of	the sender.

     If	pid is -1 and the effective user ID of the sender is not super-user,
     sig will be sent to all processes excluding proc0 and proc1 whose real
     user ID is	equal to the effective user ID of the sender.

     If	pid is -1 and the effective user ID of the sender is super-user, sig
     will be sent to all processes excluding proc0 and proc1.

     If	pid is negative	but not	-1, sig	will be	sent to	all processes whose
     process group ID is equal to the absolute value of	pid.

     If	the value of pid causes	sig to be generated for	the sending process,
     and if sig	is not blocked for the calling thread and if no	other thread
     has sig unblocked or is waiting in	a sigwait function for sig, either sig
     or	at least one pending unblocked signal shall be delivered to the
     calling thread before the kill() function returns.






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KILL(2)								       KILL(2)



     kill will fail and	no signal will be sent if one or more of the following
     are true:

     [EINVAL]	    Sig	is not a valid signal number.

     [EPERM]	    Sig	is SIGKILL and pid is 1	(proc1).

     [ESRCH]	    No process can be found corresponding to that specified by
		    pid.

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

     [EPERM]	    The	user ID	of the sending process is not super-user, and
		    its	real or	effective user ID does not match the real,
		    saved,  or effective user ID of the	receiving process.

SEE ALSO    [Toc]    [Back]

     kill(1), exec(2), getpid(2), setpgrp(2), setsid(2), signal(2), sigset(2),
     sigaction(2), sigprocmask(2), sigqueue(3),	sigwait(3), sigvec(3B),
     sigblock(3B), sigsetmask(3B), killpg(3B), pthread_kill(3P)

DIAGNOSTIC    [Toc]    [Back]

     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of	-1 is returned and errno is set	to indicate the	error.


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