kill(2)                                                             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 (pidt pid, int 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 [see signal(5)], 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 saved [from exec(2)] user ID of the receiving process unless
         the effective user ID of the sending process is superuser, [see
         intro(2)], or sig is SIGCONT and the sending process has the same
         session ID as the receiving process.

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

         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 negative but not (pidt)-1, sig will be sent to all
         processes whose process group ID is equal to the absolute value of
         pid and for which the process has permission to send a signal.

         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.  Permission is needed to send a signal to process groups.

         If pid is (pidt)-1 and the effective user ID of the sender is not
         superuser, 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 (pidt)-1 and the effective user ID of the sender is
         superuser, sig will be sent to all processes excluding proc0 and
         proc1.

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



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   kill(2)                                                             kill(2)


         EINVAL         sig is not a valid signal number.

         EINVAL         sig is SIGKILL and pid is (pidt)1 (i.e., pid
                        specifies proc1).

         ESRCH          No process or process group can be found corresponding
                        to that specified by pid.

         EPERM          The user ID of the sending process is not privileged,
                        and its real or effective user ID does not match the
                        real or saved user ID of the receiving process, and
                        the calling process is not sending SIGCONT to a
                        process that shares the same session ID.

   SEE ALSO
         getpid(2), intro(2), setpgrp(2), signal(2), getsid(2), sigsend(2),
         sigaction(2).
         kill(1) in the User's Reference Manual.

   NOTES
         sigsend is a more versatile way to send signals to processes.  The
         user is encouraged to use sigsend instead of kill.

   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.



























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