Signal.trap( signal, proc ) → obj
Signal.trap( signal ) {| | block } → obj

Specifies the handling of signals. The first parameter is a signal name (a string such as ``SIGALRM’’, ``SIGUSR1’’, and so on) or a signal number. The characters ``SIG’’ may be omitted from the signal name. The command or block specifies code to be run when the signal is raised. If the command is the string ``IGNORE’’ or ``SIG_IGN’’, the signal will be ignored. If the command is ``DEFAULT’’ or ``SIG_DFL’’, the operating system’s default handler will be invoked. If the command is ``EXIT’’, the script will be terminated by the signal. Otherwise, the given command or block will be run. The special signal name ``EXIT’’ or signal number zero will be invoked just prior to program termination. trap returns the previous handler for the given signal.

Signal.trap(0, proc { puts "Terminating: #{$$}" })
Signal.trap("CLD")  { puts "Child died" }
fork && Process.wait

produces:

Terminating: 27461
Child died
Terminating: 27460

Source Code

/*
* call-seq:
*   Signal.trap( signal, proc ) => obj
*   Signal.trap( signal ) {| | block } => obj
*
* Specifies the handling of signals. The first parameter is a signal
* name (a string such as ``SIGALRM'', ``SIGUSR1'', and so on) or a
* signal number. The characters ``SIG'' may be omitted from the
* signal name. The command or block specifies code to be run when the
* signal is raised. If the command is the string ``IGNORE'' or
* ``SIG_IGN'', the signal will be ignored. If the command is
* ``DEFAULT'' or ``SIG_DFL'', the operating system's default handler
* will be invoked. If the command is ``EXIT'', the script will be
* terminated by the signal. Otherwise, the given command or block
* will be run.
* The special signal name ``EXIT'' or signal number zero will be
* invoked just prior to program termination.
* trap returns the previous handler for the given signal.
*
*     Signal.trap(0, proc { puts "Terminating: #{$$}" })
*     Signal.trap("CLD")  { puts "Child died" }
*     fork && Process.wait
*
* produces:
*     Terminating: 27461
*     Child died
*     Terminating: 27460
*/
static VALUE
sig_trap(argc, argv)
   int argc;
   VALUE *argv;
{
   struct trap_arg arg;

   rb_secure(2);
   if (argc == 0 || argc > 2) {
       rb_raise(rb_eArgError, "wrong number of arguments -- trap(sig, cmd)/trap(sig){...}");
   }

   arg.sig = argv[0];
   if (argc == 1) {
       arg.cmd = rb_block_proc();
   }
   else if (argc == 2) {
       arg.cmd = argv[1];
   }

   if (OBJ_TAINTED(arg.cmd)) {
       rb_raise(rb_eSecurityError, "Insecure: tainted signal trap");
   }
#ifndef _WIN32
   /* disable interrupt */
# ifdef HAVE_SIGPROCMASK
   sigfillset(&arg.mask);
   sigprocmask(SIG_BLOCK, &arg.mask, &arg.mask);
# else
   arg.mask = sigblock(~0);
# endif

   return rb_ensure(trap, (VALUE)&arg, trap_ensure, (VALUE)&arg);
#else
   return trap(&arg);
#endif
}