KILL(S) UNIX System V KILL(S)
Name
kill - send a signal to a process or a group of processes
Syntax
#include <signal.h>
int kill (pid, sig)
int pid, sig;
Description
The kill system call 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(S) 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 or effective user ID of the receiving
process, unless the effective user ID of the sending process
is super-user.
The processes with a process ID of 0 and a process ID of 1
are special processes (see intro(S)) 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.
The kill system call will fail and no signal will be sent if
one or more of the following is true:
[EINVAL] sig is not a valid signal number.
[EINVAL] sig is SIGKILL and pid is 1 (proc1).
[ESRCH] No process can be found corresponding to that
specified by pid.
[EPERM] The user ID of the sending process is not
super-user, and its real or effective user ID
does not match the real or effective user ID
of the receiving process.
See Also
getpid(S), setpgrp(S), signal(S), sigset(S), kill(C)
Diagnostics
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned, and errno is set to
indicate the error.
Standards Conformance
kill is conformant with:
AT&T SVID Issue 2, Select Code 307-127;
The X/Open Portability Guide II of January 1987;
IEEE POSIX Std 1003.1-1988 with C Standard Language-
Dependent System Support;
and NIST FIPS 151-1.
(printed 6/20/89)