KILL(2) KILL(2)
NAME
kill - send a signal to a process or a group of processes
SYNOPSIS
int kill (pid, sig)
int pid, sig;
DESCRIPTION
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 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(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.
Page 1 May 1989
KILL(2) KILL(2)
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.
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.
[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(2), setpgrp(2), signal(2), sigset(2), sigaction(2).
kill(1) in the User's Reference Manual.
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.
Page 2 May 1989