KILL(2)                     BSD Programmer's Manual                    KILL(2)

NAME
     kill - send signal to a process

SYNOPSIS
     #include <sys/signal.h>

     int
     kill(pidt pid, int sig)

DESCRIPTION
     The kill() function sends the signal given by sig to pid, a process or a
     group of processes.  Sig may be one of the signals specified in sigac-
     tion(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 designated
     by pid, the real or effective user ID of the receving process must match
     that of the sending process or the user must have appropriate privileges
     (such as given by a set-user-ID program or the user is the super-user).
     A single exception is the signal SIGCONT, which may always be sent to any
     descendant of the current process.

     If pid is greater than zero:
             Sig is sent to the process whose ID is equal to pid.

     If pid is zero:
             Sig is sent to all processes whose group ID is equal to the pro-
             cess group ID of the sender, and for which the process has per-
             mission; 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. If the user is not the su-
             per user, the signal is sent to all processes with the same uid
             as the user except the process sending the signal.  No error is
             returned if any process could be signaled.

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

ERRORS
     Kill() will fail and no signal will be sent if:

     [EINVAL]  Sig is not a valid signal number.

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

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

     [EPERM]   The sending process is not the super-user and its effective us-
               er id does not match the effective user-id of the receiving
               process.  When signaling a process group, this error is re-
               turned if any members of the group could not be signaled.

SEE ALSO
     getpid(2),  getpgrp(2),  killpg(2),  sigaction(2)

STANDARDS
     The kill() function is expected to conform to IEEE Std 1003.1-1988
     (``POSIX'').

4th Berkeley Distribution       March 26, 1993                               2