builtins/trap.def

This file is trap.def, from which is created trap.c.
It implements the builtin "trap" in Bash.

Copyright (C) 1987, 1989, 1991 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

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$PRODUCES trap.c

$BUILTIN trap
$FUNCTION trap_builtin
$SHORT_DOC trap [arg] [signal_spec] or trap -l
The command ARG is to be read and executed when the shell receives
signal(s) SIGNAL_SPEC.  If ARG is absent all specified signals are
reset to their original values.  If ARG is the null string each
SIGNAL_SPEC is ignored by the shell and by the commands it invokes.
If SIGNAL_SPEC is EXIT (0) the command ARG is executed on exit from
the shell.  If SIGNAL_SPEC is DEBUG, ARG is executed after every
command.  If ARG is `-p' then the trap commands associated with
each SIGNAL_SPEC are displayed.  If no arguments are supplied or if
only `-p' is given, trap prints the list of commands associated with
each signal number.  SIGNAL_SPEC is either a signal name in <signal.h>
or a signal number.  `trap -l' prints a list of signal names and their
corresponding numbers.  Note that a signal can be sent to the shell
with "kill -signal $$".
$END

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "../bashtypes.h"
#include <signal.h>
#include <stdio.h>
#include "../bashansi.h"

#include "../shell.h"
#include "../trap.h"
#include "common.h"
#include "bashgetopt.h"

static int display_traps ();

/* The trap command:

   trap <arg> <signal ...>
   trap <signal ...>
   trap -l
   trap -p [sigspec ...]
   trap [--]

   Set things up so that ARG is executed when SIGNAL(s) N is recieved.
   If ARG is the empty string, then ignore the SIGNAL(s).  If there is
   no ARG, then set the trap for SIGNAL(s) to its original value.  Just
   plain "trap" means to print out the list of commands associated with
   each signal number.  Single arg of "-l" means list the signal names. */

/* Possible operations to perform on the list of signals.*/
#define SET 0			/* Set this signal to first_arg. */
#define REVERT 1		/* Revert to this signals original value. */
#define IGNORE 2		/* Ignore this signal. */

extern int interactive;

int
trap_builtin (list)
     WORD_LIST *list;
{
  int list_signal_names, display, result, opt;

  list_signal_names = display = 0;
  result = EXECUTION_SUCCESS;
  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "lp")) != -1)
    {
      switch (opt)
	{
	case 'l':
	  list_signal_names++;
	  break;
	case 'p':
	  display++;
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  if (list_signal_names)
    return (display_signal_list ((WORD_LIST *)NULL, 1));
  else if (display || list == 0)
    return (display_traps (list));
  else
    {
      char *first_arg;
      int operation, sig;

      operation = SET;
      first_arg = list->word->word;
      if (first_arg && *first_arg && signal_object_p (first_arg))
	operation = REVERT;
      else
	{
	  list = list->next;
	  if (*first_arg == '\0')
	    operation = IGNORE;
	  else if (first_arg[0] == '-' && !first_arg[1])
	    operation = REVERT;
	}

      while (list)
	{
	  sig = decode_signal (list->word->word);

	  if (sig == NO_SIG)
	    {
	      builtin_error ("%s: not a signal specification",
			     list->word->word);
	      result = EXECUTION_FAILURE;
	    }
	  else
	    {
	      switch (operation)
		{
		  case SET:
		    set_signal (sig, first_arg);
		    break;

		  case REVERT:
		    restore_default_signal (sig);

		    /* Signals that the shell treats specially need special
		       handling. */
		    switch (sig)
		      {
		      case SIGINT:
			if (interactive)
			  set_signal_handler (SIGINT, sigint_sighandler);
			else
			  set_signal_handler (SIGINT, termination_unwind_protect);
			break;

		      case SIGQUIT:
			/* Always ignore SIGQUIT. */
			set_signal_handler (SIGQUIT, SIG_IGN);
			break;
		      case SIGTERM:
#if defined (JOB_CONTROL)
		      case SIGTTIN:
		      case SIGTTOU:
		      case SIGTSTP:
#endif /* JOB_CONTROL */
			if (interactive)
			  set_signal_handler (sig, SIG_IGN);
			break;
		      }
		    break;

		  case IGNORE:
		    ignore_signal (sig);
		    break;
		}
	    }
	  list = list->next;
	}
    }

  return (result);
}

static void
showtrap (i)
     int i;
{
  char *t, *p;

  p = trap_list[i];

  if (p == (char *)DEFAULT_SIG)
    return;

  t = (p == (char *)IGNORE_SIG) ? (char *)NULL : single_quote (p);
  printf ("trap -- %s %s\n", t ? t : "''", signal_name (i));
  if (t)
    free (t);
}

static int
display_traps (list)
     WORD_LIST *list;
{
  int result, i;

  if (list == 0)
    {
      for (i = 0; i <= NSIG; i++)
	showtrap (i);
      return (EXECUTION_SUCCESS);
    }

  for (result = EXECUTION_SUCCESS; list; list = list->next)
    {
      i = decode_signal (list->word->word);
      if (i == NO_SIG)
	{
	  result = EXECUTION_FAILURE;
	  builtin_error ("%s: not a signal specification", list->word->word);
	}
      else
	showtrap (i);
    }

  return (result);
}