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trap.c revision 1.21 
      1 /*	$NetBSD: trap.c,v 1.21 1999/03/27 13:46:19 christos 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 #include <sys/cdefs.h>
     40 #ifndef lint
     41 #if 0
     42 static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
     43 #else
     44 __RCSID("$NetBSD: trap.c,v 1.21 1999/03/27 13:46:19 christos Exp $");
     45 #endif
     46 #endif /* not lint */
     47 
     48 #include <signal.h>
     49 #include <unistd.h>
     50 #include <stdlib.h>
     51 
     52 #include "shell.h"
     53 #include "main.h"
     54 #include "nodes.h"	/* for other headers */
     55 #include "eval.h"
     56 #include "jobs.h"
     57 #include "show.h"
     58 #include "options.h"
     59 #include "syntax.h"
     60 #include "output.h"
     61 #include "memalloc.h"
     62 #include "error.h"
     63 #include "trap.h"
     64 #include "mystring.h"
     65 
     66 
     67 /*
     68  * Sigmode records the current value of the signal handlers for the various
     69  * modes.  A value of zero means that the current handler is not known.
     70  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     71  */
     72 
     73 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     74 #define S_CATCH 2		/* signal is caught */
     75 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     76 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     77 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     78 
     79 
     80 extern char nullstr[1];		/* null string */
     81 
     82 char *trap[NSIG+1];		/* trap handler commands */
     83 MKINIT char sigmode[NSIG];	/* current value of signal */
     84 char gotsig[NSIG];		/* indicates specified signal received */
     85 int pendingsigs;			/* indicates some signal received */
     86 
     87 static int getsigaction __P((int, sig_t *));
     88 
     89 /*
     90  * The trap builtin.
     91  */
     92 
     93 int
     94 trapcmd(argc, argv)
     95 	int argc;
     96 	char **argv;
     97 {
     98 	char *action;
     99 	char **ap;
    100 	int signo;
    101 
    102 	if (argc <= 1) {
    103 		for (signo = 0 ; signo <= NSIG ; signo++) {
    104 			if (trap[signo] != NULL)
    105 				out1fmt("%d: %s\n", signo, trap[signo]);
    106 		}
    107 		return 0;
    108 	}
    109 	ap = argv + 1;
    110 	if (is_number(*ap))
    111 		action = NULL;
    112 	else
    113 		action = *ap++;
    114 	while (*ap) {
    115 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    116 			error("%s: bad trap", *ap);
    117 		INTOFF;
    118 		if (action)
    119 			action = savestr(action);
    120 		if (trap[signo])
    121 			ckfree(trap[signo]);
    122 		trap[signo] = action;
    123 		if (signo != 0)
    124 			setsignal(signo);
    125 		INTON;
    126 		ap++;
    127 	}
    128 	return 0;
    129 }
    130 
    131 
    132 
    133 /*
    134  * Clear traps on a fork.
    135  */
    136 
    137 void
    138 clear_traps() {
    139 	char **tp;
    140 
    141 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    142 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    143 			INTOFF;
    144 			ckfree(*tp);
    145 			*tp = NULL;
    146 			if (tp != &trap[0])
    147 				setsignal(tp - trap);
    148 			INTON;
    149 		}
    150 	}
    151 }
    152 
    153 
    154 
    155 /*
    156  * Set the signal handler for the specified signal.  The routine figures
    157  * out what it should be set to.
    158  */
    159 
    160 long
    161 setsignal(signo)
    162 	int signo;
    163 {
    164 	int action;
    165 	sig_t sigact = SIG_DFL;
    166 	char *t;
    167 
    168 	if ((t = trap[signo]) == NULL)
    169 		action = S_DFL;
    170 	else if (*t != '\0')
    171 		action = S_CATCH;
    172 	else
    173 		action = S_IGN;
    174 	if (rootshell && action == S_DFL) {
    175 		switch (signo) {
    176 		case SIGINT:
    177 			if (iflag || minusc || sflag == 0)
    178 				action = S_CATCH;
    179 			break;
    180 		case SIGQUIT:
    181 #ifdef DEBUG
    182 			{
    183 			extern int debug;
    184 
    185 			if (debug)
    186 				break;
    187 			}
    188 #endif
    189 			/* FALLTHROUGH */
    190 		case SIGTERM:
    191 			if (iflag)
    192 				action = S_IGN;
    193 			break;
    194 #if JOBS
    195 		case SIGTSTP:
    196 		case SIGTTOU:
    197 			if (mflag)
    198 				action = S_IGN;
    199 			break;
    200 #endif
    201 		}
    202 	}
    203 
    204 	t = &sigmode[signo - 1];
    205 	if (*t == 0) {
    206 		/*
    207 		 * current setting unknown
    208 		 */
    209 		if (!getsigaction(signo, &sigact)) {
    210 			/*
    211 			 * Pretend it worked; maybe we should give a warning
    212 			 * here, but other shells don't. We don't alter
    213 			 * sigmode, so that we retry every time.
    214 			 */
    215 			return 0;
    216 		}
    217 		if (sigact == SIG_IGN) {
    218 			if (mflag && (signo == SIGTSTP ||
    219 			     signo == SIGTTIN || signo == SIGTTOU)) {
    220 				*t = S_IGN;	/* don't hard ignore these */
    221 			} else
    222 				*t = S_HARD_IGN;
    223 		} else {
    224 			*t = S_RESET;	/* force to be set */
    225 		}
    226 	}
    227 	if (*t == S_HARD_IGN || *t == action)
    228 		return 0;
    229 	switch (action) {
    230 		case S_DFL:	sigact = SIG_DFL;	break;
    231 		case S_CATCH:  	sigact = onsig;		break;
    232 		case S_IGN:	sigact = SIG_IGN;	break;
    233 	}
    234 	*t = action;
    235 	siginterrupt(signo, 1);
    236 	return (long)signal(signo, sigact);
    237 }
    238 
    239 /*
    240  * Return the current setting for sig w/o changing it.
    241  */
    242 static int
    243 getsigaction(signo, sigact)
    244 	int signo;
    245 	sig_t *sigact;
    246 {
    247 	struct sigaction sa;
    248 
    249 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    250 		return 0;
    251 	*sigact = (sig_t) sa.sa_handler;
    252 	return 1;
    253 }
    254 
    255 /*
    256  * Ignore a signal.
    257  */
    258 
    259 void
    260 ignoresig(signo)
    261 	int signo;
    262 {
    263 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    264 		signal(signo, SIG_IGN);
    265 	}
    266 	sigmode[signo - 1] = S_HARD_IGN;
    267 }
    268 
    269 
    270 #ifdef mkinit
    271 INCLUDE <signal.h>
    272 INCLUDE "trap.h"
    273 
    274 SHELLPROC {
    275 	char *sm;
    276 
    277 	clear_traps();
    278 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    279 		if (*sm == S_IGN)
    280 			*sm = S_HARD_IGN;
    281 	}
    282 }
    283 #endif
    284 
    285 
    286 
    287 /*
    288  * Signal handler.
    289  */
    290 
    291 void
    292 onsig(signo)
    293 	int signo;
    294 {
    295 	signal(signo, onsig);
    296 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    297 		onint();
    298 		return;
    299 	}
    300 	gotsig[signo - 1] = 1;
    301 	pendingsigs++;
    302 }
    303 
    304 
    305 
    306 /*
    307  * Called to execute a trap.  Perhaps we should avoid entering new trap
    308  * handlers while we are executing a trap handler.
    309  */
    310 
    311 void
    312 dotrap() {
    313 	int i;
    314 	int savestatus;
    315 
    316 	for (;;) {
    317 		for (i = 1 ; ; i++) {
    318 			if (gotsig[i - 1])
    319 				break;
    320 			if (i >= NSIG)
    321 				goto done;
    322 		}
    323 		gotsig[i - 1] = 0;
    324 		savestatus=exitstatus;
    325 		evalstring(trap[i]);
    326 		exitstatus=savestatus;
    327 	}
    328 done:
    329 	pendingsigs = 0;
    330 }
    331 
    332 
    333 
    334 /*
    335  * Controls whether the shell is interactive or not.
    336  */
    337 
    338 
    339 void
    340 setinteractive(on)
    341 	int on;
    342 {
    343 	static int is_interactive;
    344 
    345 	if (on == is_interactive)
    346 		return;
    347 	setsignal(SIGINT);
    348 	setsignal(SIGQUIT);
    349 	setsignal(SIGTERM);
    350 	is_interactive = on;
    351 }
    352 
    353 
    354 
    355 /*
    356  * Called to exit the shell.
    357  */
    358 
    359 void
    360 exitshell(status)
    361 	int status;
    362 {
    363 	struct jmploc loc1, loc2;
    364 	char *p;
    365 
    366 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    367 	if (setjmp(loc1.loc)) {
    368 		goto l1;
    369 	}
    370 	if (setjmp(loc2.loc)) {
    371 		goto l2;
    372 	}
    373 	handler = &loc1;
    374 	if ((p = trap[0]) != NULL && *p != '\0') {
    375 		trap[0] = NULL;
    376 		evalstring(p);
    377 	}
    378 l1:   handler = &loc2;			/* probably unnecessary */
    379 	flushall();
    380 #if JOBS
    381 	setjobctl(0);
    382 #endif
    383 l2:   _exit(status);
    384 	/* NOTREACHED */
    385 }
    386