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+This file is trap.def, from which is created trap.c.
+It implements the builtin "trap" in Bash.
+
+Copyright (C) 1987-2021 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 3 of the License, 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. If not, see <http://www.gnu.org/licenses/>.
+
+$PRODUCES trap.c
+
+$BUILTIN trap
+$FUNCTION trap_builtin
+$SHORT_DOC trap [-lp] [[arg] signal_spec ...]
+Trap signals and other events.
+
+Defines and activates handlers to be run when the shell receives signals
+or other conditions.
+
+ARG is a command to be read and executed when the shell receives the
+signal(s) SIGNAL_SPEC. If ARG is absent (and a single SIGNAL_SPEC
+is supplied) or `-', each specified signal is reset to its original
+value. If ARG is the null string each SIGNAL_SPEC is ignored by the
+shell and by the commands it invokes.
+
+If a SIGNAL_SPEC is EXIT (0) ARG is executed on exit from the shell. If
+a SIGNAL_SPEC is DEBUG, ARG is executed before every simple command. If
+a SIGNAL_SPEC is RETURN, ARG is executed each time a shell function or a
+script run by the . or source builtins finishes executing. A SIGNAL_SPEC
+of ERR means to execute ARG each time a command's failure would cause the
+shell to exit when the -e option is enabled.
+
+If no arguments are supplied, trap prints the list of commands associated
+with each signal.
+
+Options:
+ -l print a list of signal names and their corresponding numbers
+ -p display the trap commands associated with each SIGNAL_SPEC
+
+Each SIGNAL_SPEC is either a signal name in <signal.h> or a signal number.
+Signal names are case insensitive and the SIG prefix is optional. A
+signal may be sent to the shell with "kill -signal $$".
+
+Exit Status:
+Returns success unless a SIGSPEC is invalid or an invalid option is given.
+$END
+
+#include <config.h>
+
+#if defined (HAVE_UNISTD_H)
+# ifdef _MINIX
+# include <sys/types.h>
+# endif
+# 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 void showtrap PARAMS((int, int));
+static int display_traps PARAMS((WORD_LIST *, int));
+
+/* 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 received.
+ 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. */
+
+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;
+ CASE_HELPOPT;
+ default:
+ builtin_usage ();
+ return (EX_USAGE);
+ }
+ }
+ list = loptend;
+
+ opt = DSIG_NOCASE|DSIG_SIGPREFIX; /* flags for decode_signal */
+
+ if (list_signal_names)
+ return (sh_chkwrite (display_signal_list ((WORD_LIST *)NULL, 1)));
+ else if (display || list == 0)
+ {
+ initialize_terminating_signals ();
+ get_all_original_signals ();
+ return (sh_chkwrite (display_traps (list, display && posixly_correct)));
+ }
+ else
+ {
+ char *first_arg;
+ int operation, sig, first_signal;
+
+ operation = SET;
+ first_arg = list->word->word;
+ first_signal = first_arg && *first_arg && all_digits (first_arg) && signal_object_p (first_arg, opt);
+
+ /* Backwards compatibility. XXX - question about whether or not we
+ should throw an error if an all-digit argument doesn't correspond
+ to a valid signal number (e.g., if it's `50' on a system with only
+ 32 signals). */
+ if (first_signal)
+ operation = REVERT;
+ /* When in posix mode, the historical behavior of looking for a
+ missing first argument is disabled. To revert to the original
+ signal handling disposition, use `-' as the first argument. */
+ else if (posixly_correct == 0 && first_arg && *first_arg &&
+ (*first_arg != '-' || first_arg[1]) &&
+ signal_object_p (first_arg, opt) && list->next == 0)
+ operation = REVERT;
+ else
+ {
+ list = list->next;
+ if (list == 0)
+ {
+ builtin_usage ();
+ return (EX_USAGE);
+ }
+ else if (*first_arg == '\0')
+ operation = IGNORE;
+ else if (first_arg[0] == '-' && !first_arg[1])
+ operation = REVERT;
+ }
+
+ /* If we're in a command substitution, we haven't freed the trap strings
+ (though we reset the signal handlers). If we're setting a trap to
+ handle a signal here, free the rest of the trap strings since they
+ don't apply any more. */
+ if (subshell_environment & SUBSHELL_RESETTRAP)
+ {
+ free_trap_strings ();
+ subshell_environment &= ~SUBSHELL_RESETTRAP;
+ }
+
+ while (list)
+ {
+ sig = decode_signal (list->word->word, opt);
+
+ if (sig == NO_SIG)
+ {
+ sh_invalidsig (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:
+ /* XXX - should we do this if original disposition
+ was SIG_IGN? */
+ if (interactive)
+ set_signal_handler (SIGINT, sigint_sighandler);
+ /* special cases for interactive == 0 */
+ else if (interactive_shell && (sourcelevel||running_trap||parse_and_execute_level))
+ set_signal_handler (SIGINT, sigint_sighandler);
+ else
+ set_signal_handler (SIGINT, termsig_sighandler);
+ 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, show_default)
+ int i, show_default;
+{
+ char *t, *p, *sn;
+ int free_t;
+
+ free_t = 1;
+ p = trap_list[i];
+ if (p == (char *)DEFAULT_SIG && signal_is_hard_ignored (i) == 0)
+ {
+ if (show_default)
+ t = "-";
+ else
+ return;
+ free_t = 0;
+ }
+ else if (signal_is_hard_ignored (i))
+ t = (char *)NULL;
+ else
+ t = (p == (char *)IGNORE_SIG) ? (char *)NULL : sh_single_quote (p);
+
+ sn = signal_name (i);
+ /* Make sure that signals whose names are unknown (for whatever reason)
+ are printed as signal numbers. */
+ if (STREQN (sn, "SIGJUNK", 7) || STREQN (sn, "unknown", 7))
+ printf ("trap -- %s %d\n", t ? t : "''", i);
+ else if (posixly_correct)
+ {
+ if (STREQN (sn, "SIG", 3))
+ printf ("trap -- %s %s\n", t ? t : "''", sn+3);
+ else
+ printf ("trap -- %s %s\n", t ? t : "''", sn);
+ }
+ else
+ printf ("trap -- %s %s\n", t ? t : "''", sn);
+
+ if (free_t)
+ FREE (t);
+}
+
+static int
+display_traps (list, show_all)
+ WORD_LIST *list;
+ int show_all;
+{
+ int result, i;
+
+ if (list == 0)
+ {
+ for (i = 0; i < BASH_NSIG; i++)
+ showtrap (i, show_all);
+ return (EXECUTION_SUCCESS);
+ }
+
+ for (result = EXECUTION_SUCCESS; list; list = list->next)
+ {
+ i = decode_signal (list->word->word, DSIG_NOCASE|DSIG_SIGPREFIX);
+ if (i == NO_SIG)
+ {
+ sh_invalidsig (list->word->word);
+ result = EXECUTION_FAILURE;
+ }
+ else
+ showtrap (i, show_all);
+ }
+
+ return (result);
+}
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