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KILL(2)                     BSD System Calls Manual                    KILL(2)

NAME
     kill -- send signal to a process

SYNOPSIS
     #include <signal.h>

     int
     kill(pid_t pid, int sig);

DESCRIPTION
     The kill() function sends the signal specified by sig to pid, a process or a group of processes.  Typi-cally, Typically,
     cally, Sig will be one of the signals specified in sigaction(2).  A value of 0, however, will cause
     error checking to be performed (with no signal being 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 receiving process must match that of the sending process or the user must have appropri-ate appropriate
     ate privileges (such as given by a set-user-ID program or the user is the super-user).  A single excep-tion exception
     tion 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 process group ID of the sender, and
             for which the process has permission; 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 and the process sending the signal.  If the user is not the super user, the signal is
             sent to all processes with the same uid as the user, excluding 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, supported signal number.

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

     [ESRCH]            No process or process group 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.

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

STANDARDS
     The kill() function is expected to conform to IEEE Std 1003.1-1988 (``POSIX.1'').

4th Berkeley Distribution       April 19, 1994       4th Berkeley Distribution

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