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KILL(2)                  DragonFly System Calls Manual                 KILL(2)


NAME

     kill -- send signal to a process


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

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

     int
     kill(pid_t 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
     sigaction(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 receiving 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
             process group ID of the sender, and for which the process has
             permission; this is a variant of killpg(3).

     If pid is -1:
             If the user has super-user privileges, the signal is sent to all
             processes excluding system processes (with P_SYSTEM flag set),
             process with ID 1 (usually init(8)), 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.

     NOTE! If the sending process is restricted by a reaper, the signal is
     further restricted to processes only within or under that reaper.  The
     reaper itself can only be signalled directly.

     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(3).


RETURN VALUES

     The kill() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable 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 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.


SEE ALSO

     getpgrp(2), getpid(2), lwp_kill(2), sigaction(2), killpg(3), raise(3),
     init(8)


STANDARDS

     The kill() function call is expected to conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').


HISTORY

     A kill() function call appeared in Version 7 AT&T UNIX.

DragonFly 4.9                  November 26, 2016                 DragonFly 4.9

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