Sprite 1984 - 1993/Sprite 1984 - 1993.iso/src/cmds/bash-1.12/dist/builtins/trap.def

Text File | 1991-10-30 | 4.7 KB | 188 lines

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.

Bash is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any later
version.

Bash is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

$PRODUCES trap.c

$BUILTIN trap
$FUNCTION trap_builtin
$SHORT_DOC trap [arg] [signal_spec]
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 this
signal 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.  The trap command with no arguments prints the list of
commands associated with each signal number.  SIGNAL_SPEC is either
a signal name in <signal.h>, or a signal number.  The syntax `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 <sys/types.h>
#include <signal.h>
#include "../shell.h"
#include "../trap.h"

/* The trap command:

   trap <arg> <signal ...>
   trap <signal ...>
   trap -l
   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. */

trap_builtin (list)
     WORD_LIST *list;
{
  register int i;
  int list_signal_names = 0;

  while (list)
    {
      if (strcmp (list->word->word, "-l") == 0)
    {
      list_signal_names++;
      list = list->next;
    }
      else if (strcmp (list->word->word, "--") == 0)
    {
      list = list->next;
      break;
    }
      else if ((*list->word->word == '-') && (list->word->word[1] != '\0'))
    {
      bad_option (list->word->word);
      return (EXECUTION_FAILURE);
    }
      else
    break;
    }

  if (!list && !list_signal_names)
    {
      for (i = 0; i < NSIG; i++)
    if (trap_list[i] != (char *)DEFAULT_SIG)
      printf ("trap -- '%s' %s\n",
          (trap_list[i] == (char *)IGNORE_SIG) ? "" : trap_list[i],
          signal_name (i));
      return (EXECUTION_SUCCESS);
    }

  if (list_signal_names)
    {
      int column = 0;

      for (i = 0; i < NSIG; i++)
    {
      printf ("%2d) %s", i, signal_name (i));
      if (++column < 4)
        printf ("\t");
      else
        {
          printf ("\n");
          column = 0;
        }
    }
      if (column != 0)
    printf ("\n");
      return (EXECUTION_SUCCESS);
    }

  if (list)
    {
      char *first_arg = list->word->word;
      int operation = SET, any_failed = 0;

      if (signal_object_p (first_arg))
    operation = REVERT;
      else
    {
      list = list->next;
      if (*first_arg == '\0')
        operation = IGNORE;
      else if (strcmp (first_arg, "-") == 0)
        operation = REVERT;
    }

      while (list)
    {
      extern int interactive;
      int sig;

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

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

          case REVERT:
            restore_default_signal (sig);

            /* Always ignore SIGQUIT. */
            if (sig == SIGQUIT)
              signal (SIGQUIT, SIG_IGN);

            /* Ignore some other signals if we are interactive. */
            if (interactive)
              {
            if (sig  == SIGTERM)
              signal (SIGTERM, SIG_IGN);

#if defined (JOB_CONTROL)
            if (sig == SIGTTIN ||
                sig == SIGTTOU ||
                sig == SIGTSTP)
              signal (sig, SIG_IGN);
#endif /* JOB_CONTROL */
              }
            break;

          case IGNORE:
            ignore_signal (sig);
            break;
        }
        }
      list = list->next;
    }
      return ((!any_failed) ? EXECUTION_SUCCESS : EXECUTION_FAILURE);
    }
}