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trap.c revision 1.7 
      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[] = "@(#)trap.c	8.1 (Berkeley) 5/31/93";
     39 #endif /* not lint */
     40 
     41 #include "shell.h"
     42 #include "main.h"
     43 #include "nodes.h"	/* for other headers */
     44 #include "eval.h"
     45 #include "jobs.h"
     46 #include "options.h"
     47 #include "syntax.h"
     48 #include "signames.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[MAXSIG+1];		/* trap handler commands */
     74 MKINIT char sigmode[MAXSIG];	/* current value of signal */
     75 char gotsig[MAXSIG];		/* indicates specified signal received */
     76 int pendingsigs;			/* indicates some signal received */
     77 
     78 /*
     79  * The trap builtin.
     80  */
     81 
     82 trapcmd(argc, argv)  char **argv; {
     83 	char *action;
     84 	char **ap;
     85 	int signo;
     86 
     87 	if (argc <= 1) {
     88 		for (signo = 0 ; signo <= MAXSIG ; signo++) {
     89 			if (trap[signo] != NULL)
     90 				out1fmt("%d: %s\n", signo, trap[signo]);
     91 		}
     92 		return 0;
     93 	}
     94 	ap = argv + 1;
     95 	if (is_number(*ap))
     96 		action = NULL;
     97 	else
     98 		action = *ap++;
     99 	while (*ap) {
    100 		if ((signo = number(*ap)) < 0 || signo > MAXSIG)
    101 			error("%s: bad trap", *ap);
    102 		INTOFF;
    103 		if (action)
    104 			action = savestr(action);
    105 		if (trap[signo])
    106 			ckfree(trap[signo]);
    107 		trap[signo] = action;
    108 		if (signo != 0)
    109 			setsignal(signo);
    110 		INTON;
    111 		ap++;
    112 	}
    113 	return 0;
    114 }
    115 
    116 
    117 
    118 /*
    119  * Clear traps on a fork.
    120  */
    121 
    122 void
    123 clear_traps() {
    124 	char **tp;
    125 
    126 	for (tp = trap ; tp <= &trap[MAXSIG] ; tp++) {
    127 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    128 			INTOFF;
    129 			ckfree(*tp);
    130 			*tp = NULL;
    131 			if (tp != &trap[0])
    132 				setsignal(tp - trap);
    133 			INTON;
    134 		}
    135 	}
    136 }
    137 
    138 
    139 
    140 /*
    141  * Set the signal handler for the specified signal.  The routine figures
    142  * out what it should be set to.
    143  */
    144 
    145 int
    146 setsignal(signo) {
    147 	int action;
    148 	sig_t sigact;
    149 	char *t;
    150 	extern void onsig();
    151 	extern sig_t getsigaction();
    152 
    153 	if ((t = trap[signo]) == NULL)
    154 		action = S_DFL;
    155 	else if (*t != '\0')
    156 		action = S_CATCH;
    157 	else
    158 		action = S_IGN;
    159 	if (rootshell && action == S_DFL) {
    160 		switch (signo) {
    161 		case SIGINT:
    162 			if (iflag)
    163 				action = S_CATCH;
    164 			break;
    165 		case SIGQUIT:
    166 #ifdef DEBUG
    167 			{
    168 			extern int debug;
    169 
    170 			if (debug)
    171 				break;
    172 			}
    173 #endif
    174 			/* FALLTHROUGH */
    175 		case SIGTERM:
    176 			if (iflag)
    177 				action = S_IGN;
    178 			break;
    179 #if JOBS
    180 		case SIGTSTP:
    181 		case SIGTTOU:
    182 			if (mflag)
    183 				action = S_IGN;
    184 			break;
    185 #endif
    186 		}
    187 	}
    188 	t = &sigmode[signo - 1];
    189 	if (*t == 0) {
    190 		/*
    191 		 * current setting unknown
    192 		 */
    193 		sigact = getsigaction(signo);
    194 		if (sigact == SIG_IGN) {
    195 			if (mflag && (signo == SIGTSTP ||
    196 			     signo == SIGTTIN || signo == SIGTTOU)) {
    197 				*t = S_IGN;	/* don't hard ignore these */
    198 			} else
    199 				*t = S_HARD_IGN;
    200 		} else {
    201 			*t = S_RESET;	/* force to be set */
    202 		}
    203 	}
    204 	if (*t == S_HARD_IGN || *t == action)
    205 		return 0;
    206 	switch (action) {
    207 		case S_DFL:	sigact = SIG_DFL;	break;
    208 		case S_CATCH:  	sigact = onsig;		break;
    209 		case S_IGN:	sigact = SIG_IGN;	break;
    210 	}
    211 	*t = action;
    212 	return (int)signal(signo, sigact);
    213 }
    214 
    215 /*
    216  * Return the current setting for sig w/o changing it.
    217  */
    218 sig_t
    219 getsigaction(signo) {
    220 	struct sigaction sa;
    221 
    222 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    223 		error("Sigaction system call failed");
    224 
    225 	return sa.sa_handler;
    226 }
    227 
    228 /*
    229  * Ignore a signal.
    230  */
    231 
    232 void
    233 ignoresig(signo) {
    234 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    235 		signal(signo, SIG_IGN);
    236 	}
    237 	sigmode[signo - 1] = S_HARD_IGN;
    238 }
    239 
    240 
    241 #ifdef mkinit
    242 INCLUDE "signames.h"
    243 INCLUDE "trap.h"
    244 
    245 SHELLPROC {
    246 	char *sm;
    247 
    248 	clear_traps();
    249 	for (sm = sigmode ; sm < sigmode + MAXSIG ; sm++) {
    250 		if (*sm == S_IGN)
    251 			*sm = S_HARD_IGN;
    252 	}
    253 }
    254 #endif
    255 
    256 
    257 
    258 /*
    259  * Signal handler.
    260  */
    261 
    262 void
    263 onsig(signo) {
    264 	signal(signo, onsig);
    265 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    266 		onint();
    267 		return;
    268 	}
    269 	gotsig[signo - 1] = 1;
    270 	pendingsigs++;
    271 }
    272 
    273 
    274 
    275 /*
    276  * Called to execute a trap.  Perhaps we should avoid entering new trap
    277  * handlers while we are executing a trap handler.
    278  */
    279 
    280 void
    281 dotrap() {
    282 	int i;
    283 	int savestatus;
    284 
    285 	for (;;) {
    286 		for (i = 1 ; ; i++) {
    287 			if (gotsig[i - 1])
    288 				break;
    289 			if (i >= MAXSIG)
    290 				goto done;
    291 		}
    292 		gotsig[i - 1] = 0;
    293 		savestatus=exitstatus;
    294 		evalstring(trap[i]);
    295 		exitstatus=savestatus;
    296 	}
    297 done:
    298 	pendingsigs = 0;
    299 }
    300 
    301 
    302 
    303 /*
    304  * Controls whether the shell is interactive or not.
    305  */
    306 
    307 
    308 void
    309 setinteractive(on) {
    310 	static int is_interactive;
    311 
    312 	if (on == is_interactive)
    313 		return;
    314 	setsignal(SIGINT);
    315 	setsignal(SIGQUIT);
    316 	setsignal(SIGTERM);
    317 	is_interactive = on;
    318 }
    319 
    320 
    321 
    322 /*
    323  * Called to exit the shell.
    324  */
    325 
    326 void
    327 exitshell(status) {
    328 	struct jmploc loc1, loc2;
    329 	char *p;
    330 
    331 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    332 	if (setjmp(loc1.loc)) {
    333 		goto l1;
    334 	}
    335 	if (setjmp(loc2.loc)) {
    336 		goto l2;
    337 	}
    338 	handler = &loc1;
    339 	if ((p = trap[0]) != NULL && *p != '\0') {
    340 		trap[0] = NULL;
    341 		evalstring(p);
    342 	}
    343 l1:   handler = &loc2;			/* probably unnecessary */
    344 	flushall();
    345 #if JOBS
    346 	setjobctl(0);
    347 #endif
    348 l2:   _exit(status);
    349 }
    350