kill(2)                        DG/UX R4.11MU05                       kill(2)


NAME
       kill - send a signal to a process

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

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

   where:
       pid    An integer (positive, negative, or zero) indicating a process
              or a group of processes to be sent the signal
       sig    A signal number that is either one from the list given in
              <signal.h> or zero

DESCRIPTION
       The kill() function sends a specified signal to a specified process
       or group of processes.  If sig is zero (the null signal), error
       checking is performed but no signal is actually sent.  The null
       signal can be used to check the validity of pid.

       If pid is greater than zero, sig shall be sent to the process whose
       process ID is equal to pid.

       If pid is zero, sig shall be sent to all processes (excluding an
       implementation-defined set of system processes) whose process group
       ID is equal to the process group ID of the sender, and for which the
       process has permission to send a signal.

       If pid is -1, the behavior of the kill() function is unspecified.

       If pid is negative, but not -1, sig shall 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 the value of pid causes sig to be generated for the sending
       process, and if sig is not blocked, either sig or at least one
       pending unblocked signal shall be delivered to the sending process
       before the kill() function returns.

       If the implementation supports the SIGCONT signal, the user ID tests
       described above shall not be applied when sending SIGCONT to a
       process that is a member of the same session as the sending process.

       The kill() function is successful if the process has permission to
       send sig to any of the processes specified by pid.  If the kill()
       function fails, no signal shall be sent.

ACCESS CONTROL
       For a process to have permission to send a signal to a process
       designated by 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 sending process has appropriate privilege.

       On a generic DG/UX system, appropriate privilege is granted by having
       an effective UID of 0 (root). See the appropriate_privilege(5) man
       page for more information.

       On a system with DG/UX information security, appropriate privilege is
       granted by having one or more specific capabilities enabled in the
       effective capability set of the user.  See cap_defaults(5) for the
       default capabilities for this command.

       If {_POSIX_SAVED_IDS} is defined, the saved set-user-ID of the
       receiving process shall be checked in place of its effective user ID.
       If a receiving process's effective user ID has been altered through
       use of the S_ISUID mode bit (see <sys/stat.h>), the implementation
       may still permit the application to receive a signal sent by the
       parent process or by a process with the same real user ID.

       An implementation that provides extended security controls may impose
       further implementation-defined restrictions on the sending of
       signals, including the null signal.  In particular, the system may
       deny the existence of some or all of the processes specified by pid.

RETURN VALUE
       0      Successful completion.

       -1     An error occurred.  errno is set to indicate the error.

DIAGNOSTICS
       If any of the following conditions occur, the kill() function shall
       return -1 and set errno to the corresponding value:

       EINVAL    The value of the sig argument is an invalid or unsupported
                 signal number.

       EPERM     The process does not have permission to send the signal to
                 any receiving process.

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

SEE ALSO
       getpid(2), setsid(2), sigaction(2), <signal.h>, cap_defaults(5).

COPYRIGHTS
       Portions of this text are reprinted from IEEE Std 1003.1-1988,
       Portable Operating System Interface for Computer Environment,
       copyright © 1988 by the Institute of Electrical and Electronics
       Engineers, Inc., with the permission of the IEEE Standards
       Department.  To purchase IEEE Standards, call 800/678-IEEE.

       In the event of a discrepancy between the electronic and the original
       printed version, the original version takes precedence.

STANDARDS
       Since _POSIX_SAVED_IDS is defined in the DG/UX System, the saved set-
       user-ID of the receiving process shall be checked in place of its
       effective user ID.

       If a receiving process's effective user ID has been altered through
       the use of the S_ISUID mode bit, the system permits the application
       to receive a signal sent by the parent process or by a process with
       the same real user ID.

       If pid is -1, the behavior of kill() depends on the privilege held by
       the calling process.  If the calling process has appropriate
       privilege, the signal will be sent to all processes except for the
       initialization process (PID 1).  Otherwise, the signal will be sent
       to all processes (again excluding init) whose real user ID is equal
       to the effective user ID of the sending process.

       There is one special system process that is unaffected by all calls
       of the form kill(0, sig).  This is the system initialization process,
       which has PID 1.

       The SIGCONT signal is supported.

       The signal SIGKILL cannot be successfully sent to the system
       initialization process (PID 1).


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