KILL(2)                              SysV                              KILL(2)



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

SYNOPSIS
     #include <sys/types.h>

     #include <signal.h>

     int kill (pid, sig)
     pid_t pid;
     int sig;

DESCRIPTION
     kill sends a signal to the process or group of processes specified by
     pid.  The signal to be sent is specified by sig, and is either 0 or some
     other value described in signal(2).  If sig is 0 (the null signal), kill
     performs error checking but does not send a signal.  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.

     The behavior of kill depends upon the value of pid:

     +  If pid is greater than 0, 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 pid is -1, the sending process is sent the signal along with all
        other processes for which the sending process has permission to send
        the signal.  Prior to SR10.4, the sending process was not sent the
        signal.

NOTE
     No process under Domain/OS SysV has an ID of 0.

ERRORS
     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).
     kill(1) in the SysV Command Reference.

DIAGNOSTICS
     A successful call returns 0.  A failed call returns -1 and sets errno as
     indicated under "Errors."