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trap.c revision 1.12 
      1 /*	$NetBSD: trap.c,v 1.12 1995/03/21 09:10:25 cgd Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Kenneth Almquist.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #ifndef lint
     40 #if 0
     41 static char sccsid[] = "@(#)trap.c	8.1 (Berkeley) 5/31/93";
     42 #else
     43 static char rcsid[] = "$NetBSD: trap.c,v 1.12 1995/03/21 09:10:25 cgd Exp $";
     44 #endif
     45 #endif /* not lint */
     46 
     47 #include "shell.h"
     48 #include "main.h"
     49 #include "nodes.h"	/* for other headers */
     50 #include "eval.h"
     51 #include "jobs.h"
     52 #include "options.h"
     53 #include "syntax.h"
     54 #include "output.h"
     55 #include "memalloc.h"
     56 #include "error.h"
     57 #include "trap.h"
     58 #include "mystring.h"
     59 #include <signal.h>
     60 #include <unistd.h>
     61 
     62 
     63 /*
     64  * Sigmode records the current value of the signal handlers for the various
     65  * modes.  A value of zero means that the current handler is not known.
     66  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     67  */
     68 
     69 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     70 #define S_CATCH 2		/* signal is caught */
     71 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     72 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     73 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     74 
     75 
     76 extern char nullstr[1];		/* null string */
     77 
     78 char *trap[NSIG+1];		/* trap handler commands */
     79 MKINIT char sigmode[NSIG];	/* current value of signal */
     80 char gotsig[NSIG];		/* indicates specified signal received */
     81 int pendingsigs;			/* indicates some signal received */
     82 
     83 /*
     84  * The trap builtin.
     85  */
     86 
     87 int
     88 trapcmd(argc, argv)
     89 	int argc;
     90 	char **argv;
     91 {
     92 	char *action;
     93 	char **ap;
     94 	int signo;
     95 
     96 	if (argc <= 1) {
     97 		for (signo = 0 ; signo <= NSIG ; signo++) {
     98 			if (trap[signo] != NULL)
     99 				out1fmt("%d: %s\n", signo, trap[signo]);
    100 		}
    101 		return 0;
    102 	}
    103 	ap = argv + 1;
    104 	if (is_number(*ap))
    105 		action = NULL;
    106 	else
    107 		action = *ap++;
    108 	while (*ap) {
    109 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    110 			error("%s: bad trap", *ap);
    111 		INTOFF;
    112 		if (action)
    113 			action = savestr(action);
    114 		if (trap[signo])
    115 			ckfree(trap[signo]);
    116 		trap[signo] = action;
    117 		if (signo != 0)
    118 			setsignal(signo);
    119 		INTON;
    120 		ap++;
    121 	}
    122 	return 0;
    123 }
    124 
    125 
    126 
    127 /*
    128  * Clear traps on a fork.
    129  */
    130 
    131 void
    132 clear_traps() {
    133 	char **tp;
    134 
    135 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    136 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    137 			INTOFF;
    138 			ckfree(*tp);
    139 			*tp = NULL;
    140 			if (tp != &trap[0])
    141 				setsignal(tp - trap);
    142 			INTON;
    143 		}
    144 	}
    145 }
    146 
    147 
    148 
    149 /*
    150  * Set the signal handler for the specified signal.  The routine figures
    151  * out what it should be set to.
    152  */
    153 
    154 long
    155 setsignal(signo)
    156 	int signo;
    157 {
    158 	int action;
    159 	sig_t sigact;
    160 	char *t;
    161 	extern void onsig();
    162 	extern sig_t getsigaction();
    163 
    164 	if ((t = trap[signo]) == NULL)
    165 		action = S_DFL;
    166 	else if (*t != '\0')
    167 		action = S_CATCH;
    168 	else
    169 		action = S_IGN;
    170 	if (rootshell && action == S_DFL) {
    171 		switch (signo) {
    172 		case SIGINT:
    173 			if (iflag)
    174 				action = S_CATCH;
    175 			break;
    176 		case SIGQUIT:
    177 #ifdef DEBUG
    178 			{
    179 			extern int debug;
    180 
    181 			if (debug)
    182 				break;
    183 			}
    184 #endif
    185 			/* FALLTHROUGH */
    186 		case SIGTERM:
    187 			if (iflag)
    188 				action = S_IGN;
    189 			break;
    190 #if JOBS
    191 		case SIGTSTP:
    192 		case SIGTTOU:
    193 			if (mflag)
    194 				action = S_IGN;
    195 			break;
    196 #endif
    197 		}
    198 	}
    199 	t = &sigmode[signo - 1];
    200 	if (*t == 0) {
    201 		/*
    202 		 * current setting unknown
    203 		 */
    204 		sigact = getsigaction(signo);
    205 		if (sigact == SIG_IGN) {
    206 			if (mflag && (signo == SIGTSTP ||
    207 			     signo == SIGTTIN || signo == SIGTTOU)) {
    208 				*t = S_IGN;	/* don't hard ignore these */
    209 			} else
    210 				*t = S_HARD_IGN;
    211 		} else {
    212 			*t = S_RESET;	/* force to be set */
    213 		}
    214 	}
    215 	if (*t == S_HARD_IGN || *t == action)
    216 		return 0;
    217 	switch (action) {
    218 		case S_DFL:	sigact = SIG_DFL;	break;
    219 		case S_CATCH:  	sigact = onsig;		break;
    220 		case S_IGN:	sigact = SIG_IGN;	break;
    221 	}
    222 	*t = action;
    223 	return (long)signal(signo, sigact);
    224 }
    225 
    226 /*
    227  * Return the current setting for sig w/o changing it.
    228  */
    229 sig_t
    230 getsigaction(signo)
    231 	int signo;
    232 {
    233 	struct sigaction sa;
    234 
    235 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    236 		error("Sigaction system call failed");
    237 
    238 	return sa.sa_handler;
    239 }
    240 
    241 /*
    242  * Ignore a signal.
    243  */
    244 
    245 void
    246 ignoresig(signo)
    247 	int signo;
    248 {
    249 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    250 		signal(signo, SIG_IGN);
    251 	}
    252 	sigmode[signo - 1] = S_HARD_IGN;
    253 }
    254 
    255 
    256 #ifdef mkinit
    257 INCLUDE <signal.h>
    258 INCLUDE "trap.h"
    259 
    260 SHELLPROC {
    261 	char *sm;
    262 
    263 	clear_traps();
    264 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    265 		if (*sm == S_IGN)
    266 			*sm = S_HARD_IGN;
    267 	}
    268 }
    269 #endif
    270 
    271 
    272 
    273 /*
    274  * Signal handler.
    275  */
    276 
    277 void
    278 onsig(signo)
    279 	int signo;
    280 {
    281 	signal(signo, onsig);
    282 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    283 		onint();
    284 		return;
    285 	}
    286 	gotsig[signo - 1] = 1;
    287 	pendingsigs++;
    288 }
    289 
    290 
    291 
    292 /*
    293  * Called to execute a trap.  Perhaps we should avoid entering new trap
    294  * handlers while we are executing a trap handler.
    295  */
    296 
    297 void
    298 dotrap() {
    299 	int i;
    300 	int savestatus;
    301 
    302 	for (;;) {
    303 		for (i = 1 ; ; i++) {
    304 			if (gotsig[i - 1])
    305 				break;
    306 			if (i >= NSIG)
    307 				goto done;
    308 		}
    309 		gotsig[i - 1] = 0;
    310 		savestatus=exitstatus;
    311 		evalstring(trap[i]);
    312 		exitstatus=savestatus;
    313 	}
    314 done:
    315 	pendingsigs = 0;
    316 }
    317 
    318 
    319 
    320 /*
    321  * Controls whether the shell is interactive or not.
    322  */
    323 
    324 
    325 void
    326 setinteractive(on)
    327 	int on;
    328 {
    329 	static int is_interactive;
    330 
    331 	if (on == is_interactive)
    332 		return;
    333 	setsignal(SIGINT);
    334 	setsignal(SIGQUIT);
    335 	setsignal(SIGTERM);
    336 	is_interactive = on;
    337 }
    338 
    339 
    340 
    341 /*
    342  * Called to exit the shell.
    343  */
    344 
    345 void
    346 exitshell(status)
    347 	int status;
    348 {
    349 	struct jmploc loc1, loc2;
    350 	char *p;
    351 
    352 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    353 	if (setjmp(loc1.loc)) {
    354 		goto l1;
    355 	}
    356 	if (setjmp(loc2.loc)) {
    357 		goto l2;
    358 	}
    359 	handler = &loc1;
    360 	if ((p = trap[0]) != NULL && *p != '\0') {
    361 		trap[0] = NULL;
    362 		evalstring(p);
    363 	}
    364 l1:   handler = &loc2;			/* probably unnecessary */
    365 	flushall();
    366 #if JOBS
    367 	setjobctl(0);
    368 #endif
    369 l2:   _exit(status);
    370 }
    371