kill(2)                          UNIX System V                          kill(2)


NAME
      kill - send a signal to a process or a group of processes

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

      int kill (pid_t pid, int sig);

DESCRIPTION
      kill sends a signal to a process or a group of processes.  The process or
      group of processes to which the signal is to be sent is specified by pid.
      The signal that is to be sent is specified by sig and is either one from
      the list given in signal [see signal(5)], or 0.  If sig is 0 (the null
      signal), error checking is performed but no signal is actually sent.
      This can be used to check the validity of pid.

      The real or effective user ID of the sending process must match the real
      or saved [from exec(2)] user ID of the receiving process unless the
      effective user ID of the sending process is superuser, [see intro(2)], or
      sig is SIGCONT and the sending process has the same session ID as the
      receiving process.

      The process with ID 0 and the process with ID 1 are special processes
      [see intro(2)] and will be referred to below as proc0 and proc1,
      respectively.

      If pid is greater than 0, sig will be sent to the process whose process
      ID is equal to pid.  pid may equal 1.

      If pid is negative but not (pid_t)-1, sig will 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 pid is 0, sig will be sent to all processes excluding proc0 and proc1
      whose process group ID is equal to the process group ID of the sender.
      Permission is needed to send a signal to process groups.

      If pid is (pid_t)-1 and the effective user ID of the sender is not
      superuser, sig will be sent to all processes excluding proc0 and proc1
      whose real user ID is equal to the effective user ID of the sender.

      If pid is (pid_t)-1 and the effective user ID of the sender is superuser,
      sig will be sent to all processes excluding proc0 and proc1.

      kill will fail and no signal will be sent if one or more of the following
      are true:

      EINVAL         sig is not a valid signal number.





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kill(2)                          UNIX System V                          kill(2)


      EINVAL         sig is SIGKILL and pid is (pid_t)1 (i.e., pid specifies
                     proc1).

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

      EPERM          The user ID of the sending process is not privileged, and
                     its real or effective user ID does not match the real or
                     saved user ID of the receiving process, and the calling
                     process is not sending SIGCONT to a process that shares
                     the same session ID.

SEE ALSO
      getpid(2), intro(2), setpgrp(2), signal(2), getsid(2), sigsend(2),
      sigaction(2).
      kill(1) in the User's Reference Manual.

NOTES
      sigsend is a more versatile way to send signals to processes.  The user
      is encouraged to use sigsend instead of kill.

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






























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