ultrix man page for kill

kill(2) 							System Calls Manual							   kill(2)

Name
       kill - send signal to a process

Syntax
       #include <sys/types.h>
       #include <signal.h>

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

Description
       The  system  call sends the signal sig to a process specified by the process number pid.  The sig can be a signal specified in a call or it
       can be 0.  If the sig is 0, error checking is performed, but a signal is not sent.  This call can be used to check the validity of pid.

       The sending and receiving processes must have the same effective user ID, otherwise this call is  restricted  to  the  superuser  with  the
       exception of the signal SIGCONT.  The signal SIGCONT can always be sent to a child or grandchild of the current process.

       If the process number is 0, the signal is sent to all other processes in the sender's process group.

       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.

       The above two options are variants of

       If the process number is -1, and the user is the superuser, the signal is broadcast for all processes except to system  processes  and  the
       process sending the signal.

       Processes may send signals to themselves.

Environment
       System Five
       POSIX

       When  your  program  is	compiled in the System V or POSIX environment, a signal is sent if either the real or effective uid of the sending
       process matches the real or saved-set-uid (as described in ) of the receiving process. In addition, any process can use a pid  of  -1,  and
       the signal is sent to all processes subject to these permission checks.

       In POSIX mode, the pid argument is of type pid_t.

Return Values
       Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned, and is set to indicate the error.

Diagnostics
       The system call fails under the following conditions:

       [EINVAL]       The sig is not a valid signal number.

       [EPERM]	      The  sending  process  is not the superuser, and its effective user ID does not match the effective user ID of the receiving
		      process.

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

See Also
       execve(2), getpgrp(2), getpid(2), killpg(2), sigvec(2), pause(3)

																	   kill(2)