1 This file is trap.def, from which is created trap.c.
2 It implements the builtin "trap" in Bash.
4 Copyright (C) 1987-2010 Free Software Foundation, Inc.
6 This file is part of GNU Bash, the Bourne Again SHell.
8 Bash is free software: you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation, either version 3 of the License, or
11 (at your option) any later version.
13 Bash is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with Bash. If not, see <http://www.gnu.org/licenses/>.
24 $FUNCTION trap_builtin
25 $SHORT_DOC trap [-lp] [[arg] signal_spec ...]
26 Trap signals and other events.
28 Defines and activates handlers to be run when the shell receives signals
31 ARG is a command to be read and executed when the shell receives the
32 signal(s) SIGNAL_SPEC. If ARG is absent (and a single SIGNAL_SPEC
33 is supplied) or `-', each specified signal is reset to its original
34 value. If ARG is the null string each SIGNAL_SPEC is ignored by the
35 shell and by the commands it invokes.
37 If a SIGNAL_SPEC is EXIT (0) ARG is executed on exit from the shell. If
38 a SIGNAL_SPEC is DEBUG, ARG is executed before every simple command. If
39 a SIGNAL_SPEC is RETURN, ARG is executed each time a shell function or a
40 script run by the . or source builtins finishes executing. A SIGNAL_SPEC
41 of ERR means to execute ARG each time a command's failure would cause the
42 shell to exit when the -e option is enabled.
44 If no arguments are supplied, trap prints the list of commands associated
48 -l print a list of signal names and their corresponding numbers
49 -p display the trap commands associated with each SIGNAL_SPEC
51 Each SIGNAL_SPEC is either a signal name in <signal.h> or a signal number.
52 Signal names are case insensitive and the SIG prefix is optional. A
53 signal may be sent to the shell with "kill -signal $$".
56 Returns success unless a SIGSPEC is invalid or an invalid option is given.
61 #if defined (HAVE_UNISTD_H)
63 # include <sys/types.h>
68 #include "../bashtypes.h"
71 #include "../bashansi.h"
76 #include "bashgetopt.h"
78 static void showtrap __P((int));
79 static int display_traps __P((WORD_LIST *));
83 trap <arg> <signal ...>
89 Set things up so that ARG is executed when SIGNAL(s) N is recieved.
90 If ARG is the empty string, then ignore the SIGNAL(s). If there is
91 no ARG, then set the trap for SIGNAL(s) to its original value. Just
92 plain "trap" means to print out the list of commands associated with
93 each signal number. Single arg of "-l" means list the signal names. */
95 /* Possible operations to perform on the list of signals.*/
96 #define SET 0 /* Set this signal to first_arg. */
97 #define REVERT 1 /* Revert to this signals original value. */
98 #define IGNORE 2 /* Ignore this signal. */
100 extern int posixly_correct, subshell_environment;
106 int list_signal_names, display, result, opt;
108 list_signal_names = display = 0;
109 result = EXECUTION_SUCCESS;
111 reset_internal_getopt ();
112 while ((opt = internal_getopt (list, "lp")) != -1)
129 opt = DSIG_NOCASE|DSIG_SIGPREFIX; /* flags for decode_signal */
131 if (list_signal_names)
132 return (sh_chkwrite (display_signal_list ((WORD_LIST *)NULL, 1)));
133 else if (display || list == 0)
135 initialize_terminating_signals ();
136 get_all_original_signals ();
137 return (sh_chkwrite (display_traps (list)));
142 int operation, sig, first_signal;
145 first_arg = list->word->word;
146 first_signal = first_arg && *first_arg && all_digits (first_arg) && signal_object_p (first_arg, opt);
148 /* Backwards compatibility. XXX - question about whether or not we
149 should throw an error if an all-digit argument doesn't correspond
150 to a valid signal number (e.g., if it's `50' on a system with only
154 /* When in posix mode, the historical behavior of looking for a
155 missing first argument is disabled. To revert to the original
156 signal handling disposition, use `-' as the first argument. */
157 else if (posixly_correct == 0 && first_arg && *first_arg &&
158 (*first_arg != '-' || first_arg[1]) &&
159 signal_object_p (first_arg, opt) && list->next == 0)
169 else if (*first_arg == '\0')
171 else if (first_arg[0] == '-' && !first_arg[1])
175 /* If we're in a command substitution, we haven't freed the trap strings
176 (though we reset the signal handlers). If we're setting a trap to
177 handle a signal here, free the rest of the trap strings since they
178 don't apply any more. */
179 if (subshell_environment & SUBSHELL_RESETTRAP)
181 free_trap_strings ();
182 subshell_environment &= ~SUBSHELL_RESETTRAP;
187 sig = decode_signal (list->word->word, opt);
191 sh_invalidsig (list->word->word);
192 result = EXECUTION_FAILURE;
199 set_signal (sig, first_arg);
203 restore_default_signal (sig);
205 /* Signals that the shell treats specially need special
210 /* XXX - should we do this if original disposition
213 set_signal_handler (SIGINT, sigint_sighandler);
215 set_signal_handler (SIGINT, termsig_sighandler);
219 /* Always ignore SIGQUIT. */
220 set_signal_handler (SIGQUIT, SIG_IGN);
223 #if defined (JOB_CONTROL)
227 #endif /* JOB_CONTROL */
229 set_signal_handler (sig, SIG_IGN);
253 if (p == (char *)DEFAULT_SIG && signal_is_hard_ignored (i) == 0)
255 else if (signal_is_hard_ignored (i))
258 t = (p == (char *)IGNORE_SIG) ? (char *)NULL : sh_single_quote (p);
260 sn = signal_name (i);
261 /* Make sure that signals whose names are unknown (for whatever reason)
262 are printed as signal numbers. */
263 if (STREQN (sn, "SIGJUNK", 7) || STREQN (sn, "unknown", 7))
264 printf ("trap -- %s %d\n", t ? t : "''", i);
265 else if (posixly_correct)
267 if (STREQN (sn, "SIG", 3))
268 printf ("trap -- %s %s\n", t ? t : "''", sn+3);
270 printf ("trap -- %s %s\n", t ? t : "''", sn);
273 printf ("trap -- %s %s\n", t ? t : "''", sn);
286 for (i = 0; i < BASH_NSIG; i++)
288 return (EXECUTION_SUCCESS);
291 for (result = EXECUTION_SUCCESS; list; list = list->next)
293 i = decode_signal (list->word->word, DSIG_NOCASE|DSIG_SIGPREFIX);
296 sh_invalidsig (list->word->word);
297 result = EXECUTION_FAILURE;