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trap.c revision 1.11 
      1 /*-
      2  * Copyright (c) 1991, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Kenneth Almquist.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #ifndef lint
     38 /*static char sccsid[] = "from: @(#)trap.c	8.1 (Berkeley) 5/31/93";*/
     39 static char *rcsid = "$Id: trap.c,v 1.11 1994/12/23 13:24:43 cgd Exp $";
     40 #endif /* not lint */
     41 
     42 #include "shell.h"
     43 #include "main.h"
     44 #include "nodes.h"	/* for other headers */
     45 #include "eval.h"
     46 #include "jobs.h"
     47 #include "options.h"
     48 #include "syntax.h"
     49 #include "output.h"
     50 #include "memalloc.h"
     51 #include "error.h"
     52 #include "trap.h"
     53 #include "mystring.h"
     54 #include <signal.h>
     55 #include <unistd.h>
     56 
     57 
     58 /*
     59  * Sigmode records the current value of the signal handlers for the various
     60  * modes.  A value of zero means that the current handler is not known.
     61  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     62  */
     63 
     64 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     65 #define S_CATCH 2		/* signal is caught */
     66 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     67 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     68 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     69 
     70 
     71 extern char nullstr[1];		/* null string */
     72 
     73 char *trap[NSIG+1];		/* trap handler commands */
     74 MKINIT char sigmode[NSIG];	/* current value of signal */
     75 char gotsig[NSIG];		/* indicates specified signal received */
     76 int pendingsigs;			/* indicates some signal received */
     77 
     78 /*
     79  * The trap builtin.
     80  */
     81 
     82 int
     83 trapcmd(argc, argv)
     84 	int argc;
     85 	char **argv;
     86 {
     87 	char *action;
     88 	char **ap;
     89 	int signo;
     90 
     91 	if (argc <= 1) {
     92 		for (signo = 0 ; signo <= NSIG ; signo++) {
     93 			if (trap[signo] != NULL)
     94 				out1fmt("%d: %s\n", signo, trap[signo]);
     95 		}
     96 		return 0;
     97 	}
     98 	ap = argv + 1;
     99 	if (is_number(*ap))
    100 		action = NULL;
    101 	else
    102 		action = *ap++;
    103 	while (*ap) {
    104 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    105 			error("%s: bad trap", *ap);
    106 		INTOFF;
    107 		if (action)
    108 			action = savestr(action);
    109 		if (trap[signo])
    110 			ckfree(trap[signo]);
    111 		trap[signo] = action;
    112 		if (signo != 0)
    113 			setsignal(signo);
    114 		INTON;
    115 		ap++;
    116 	}
    117 	return 0;
    118 }
    119 
    120 
    121 
    122 /*
    123  * Clear traps on a fork.
    124  */
    125 
    126 void
    127 clear_traps() {
    128 	char **tp;
    129 
    130 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    131 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    132 			INTOFF;
    133 			ckfree(*tp);
    134 			*tp = NULL;
    135 			if (tp != &trap[0])
    136 				setsignal(tp - trap);
    137 			INTON;
    138 		}
    139 	}
    140 }
    141 
    142 
    143 
    144 /*
    145  * Set the signal handler for the specified signal.  The routine figures
    146  * out what it should be set to.
    147  */
    148 
    149 long
    150 setsignal(signo)
    151 	int signo;
    152 {
    153 	int action;
    154 	sig_t sigact;
    155 	char *t;
    156 	extern void onsig();
    157 	extern sig_t getsigaction();
    158 
    159 	if ((t = trap[signo]) == NULL)
    160 		action = S_DFL;
    161 	else if (*t != '\0')
    162 		action = S_CATCH;
    163 	else
    164 		action = S_IGN;
    165 	if (rootshell && action == S_DFL) {
    166 		switch (signo) {
    167 		case SIGINT:
    168 			if (iflag)
    169 				action = S_CATCH;
    170 			break;
    171 		case SIGQUIT:
    172 #ifdef DEBUG
    173 			{
    174 			extern int debug;
    175 
    176 			if (debug)
    177 				break;
    178 			}
    179 #endif
    180 			/* FALLTHROUGH */
    181 		case SIGTERM:
    182 			if (iflag)
    183 				action = S_IGN;
    184 			break;
    185 #if JOBS
    186 		case SIGTSTP:
    187 		case SIGTTOU:
    188 			if (mflag)
    189 				action = S_IGN;
    190 			break;
    191 #endif
    192 		}
    193 	}
    194 	t = &sigmode[signo - 1];
    195 	if (*t == 0) {
    196 		/*
    197 		 * current setting unknown
    198 		 */
    199 		sigact = getsigaction(signo);
    200 		if (sigact == SIG_IGN) {
    201 			if (mflag && (signo == SIGTSTP ||
    202 			     signo == SIGTTIN || signo == SIGTTOU)) {
    203 				*t = S_IGN;	/* don't hard ignore these */
    204 			} else
    205 				*t = S_HARD_IGN;
    206 		} else {
    207 			*t = S_RESET;	/* force to be set */
    208 		}
    209 	}
    210 	if (*t == S_HARD_IGN || *t == action)
    211 		return 0;
    212 	switch (action) {
    213 		case S_DFL:	sigact = SIG_DFL;	break;
    214 		case S_CATCH:  	sigact = onsig;		break;
    215 		case S_IGN:	sigact = SIG_IGN;	break;
    216 	}
    217 	*t = action;
    218 	return (long)signal(signo, sigact);
    219 }
    220 
    221 /*
    222  * Return the current setting for sig w/o changing it.
    223  */
    224 sig_t
    225 getsigaction(signo)
    226 	int signo;
    227 {
    228 	struct sigaction sa;
    229 
    230 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    231 		error("Sigaction system call failed");
    232 
    233 	return sa.sa_handler;
    234 }
    235 
    236 /*
    237  * Ignore a signal.
    238  */
    239 
    240 void
    241 ignoresig(signo)
    242 	int signo;
    243 {
    244 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    245 		signal(signo, SIG_IGN);
    246 	}
    247 	sigmode[signo - 1] = S_HARD_IGN;
    248 }
    249 
    250 
    251 #ifdef mkinit
    252 INCLUDE <signal.h>
    253 INCLUDE "trap.h"
    254 
    255 SHELLPROC {
    256 	char *sm;
    257 
    258 	clear_traps();
    259 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    260 		if (*sm == S_IGN)
    261 			*sm = S_HARD_IGN;
    262 	}
    263 }
    264 #endif
    265 
    266 
    267 
    268 /*
    269  * Signal handler.
    270  */
    271 
    272 void
    273 onsig(signo)
    274 	int signo;
    275 {
    276 	signal(signo, onsig);
    277 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    278 		onint();
    279 		return;
    280 	}
    281 	gotsig[signo - 1] = 1;
    282 	pendingsigs++;
    283 }
    284 
    285 
    286 
    287 /*
    288  * Called to execute a trap.  Perhaps we should avoid entering new trap
    289  * handlers while we are executing a trap handler.
    290  */
    291 
    292 void
    293 dotrap() {
    294 	int i;
    295 	int savestatus;
    296 
    297 	for (;;) {
    298 		for (i = 1 ; ; i++) {
    299 			if (gotsig[i - 1])
    300 				break;
    301 			if (i >= NSIG)
    302 				goto done;
    303 		}
    304 		gotsig[i - 1] = 0;
    305 		savestatus=exitstatus;
    306 		evalstring(trap[i]);
    307 		exitstatus=savestatus;
    308 	}
    309 done:
    310 	pendingsigs = 0;
    311 }
    312 
    313 
    314 
    315 /*
    316  * Controls whether the shell is interactive or not.
    317  */
    318 
    319 
    320 void
    321 setinteractive(on)
    322 	int on;
    323 {
    324 	static int is_interactive;
    325 
    326 	if (on == is_interactive)
    327 		return;
    328 	setsignal(SIGINT);
    329 	setsignal(SIGQUIT);
    330 	setsignal(SIGTERM);
    331 	is_interactive = on;
    332 }
    333 
    334 
    335 
    336 /*
    337  * Called to exit the shell.
    338  */
    339 
    340 void
    341 exitshell(status)
    342 	int status;
    343 {
    344 	struct jmploc loc1, loc2;
    345 	char *p;
    346 
    347 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    348 	if (setjmp(loc1.loc)) {
    349 		goto l1;
    350 	}
    351 	if (setjmp(loc2.loc)) {
    352 		goto l2;
    353 	}
    354 	handler = &loc1;
    355 	if ((p = trap[0]) != NULL && *p != '\0') {
    356 		trap[0] = NULL;
    357 		evalstring(p);
    358 	}
    359 l1:   handler = &loc2;			/* probably unnecessary */
    360 	flushall();
    361 #if JOBS
    362 	setjobctl(0);
    363 #endif
    364 l2:   _exit(status);
    365 }
    366