NAME    [Toc]    [Back]

     kill - send signal to a process

SYNOPSIS    [Toc]    [Back]

     #include <signal.h>

     int
     kill(pid_t pid, int sig);

DESCRIPTION    [Toc]    [Back]

     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
superuser).  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 superuser privileges, the signal  is
sent to all
             processes excluding system processes and the process
sending the
             signal.  If the user is not the superuser, 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.

     Setuid  and setgid processes are dealt with slightly differently.  For the
     non-root user, to prevent attacks  against  such  processes,
some signal deliveries
  are not permitted and return the error EPERM.  The
following
     signals are allowed through  to  this  class  of  processes:
SIGKILL, SIGINT,
     SIGTERM,  SIGSTOP,  SIGTTIN,  SIGTTOU,  SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2.

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     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  superuser  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    [Toc]    [Back]

     getpgrp(2), getpid(2), sigaction(2), killpg(3), raise(3)

STANDARDS    [Toc]    [Back]

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

OpenBSD      3.6                          April      19,     1994