kill - send signal to a process


SYNOPSIS

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

       int kill(pid_t pid, int sig);


DESCRIPTION

       The kill system call can be used to send any signal to any
       process group or process.

       If pid is positive, then signal sig is sent to pid.

       If pid equals 0, then sig is sent to every process in  the
       process group of the current process.

       If pid equals -1, then sig is sent to every process except
       for the first one.

       If pid is less than -1, then sig is sent to every  process
       in the process group -pid.

       If sig is 0, then no signal is sent, but error checking is
       still performed.


RETURN VALUE

       On success, zero is returned.  On error, -1  is  returned,
       and errno is set appropriately.


ERRORS

       EINVAL An invalid signal was specified.

       ESRCH  The pid or process group does not exist.  Note that
              an existing process might be a  zombie,  a  process
              which  already  committed  termination, but has not
              yet been wait()ed for.

       EPERM  The process does not have permission  to  send  the
              signal  to  any  of the receiving processes.  For a
              process to have permission to send a signal to pro­
              cess  pid  it  must either have root privileges, or
              the real or effective user ID of the  sending  pro­
              cess  must  equal  the real or saved set-user-ID of
              the receiving process.  In the case of  SIGCONT  it
              suffices  when  the sending and receiving processes
              belong to the same session.


BUGS

       It is impossible to send a signal to task number one,  the
       init process, for which it has not installed a signal han­
       dler.  This is done to assure the system  is  not  brought
       down accidentally.

       SVr4, SVID, POSIX.1, X/OPEN, BSD 4.3


SEE ALSO

       _exit(2), exit(3), signal(2), signal(7)


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