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trap.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1991 The Regents of the University of California.
      3  * 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	5.2 (Berkeley) 4/12/91";
     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 
     56 
     57 /*
     58  * Sigmode records the current value of the signal handlers for the various
     59  * modes.  A value of zero means that the current handler is not known.
     60  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     61  */
     62 
     63 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     64 #define S_CATCH 2		/* signal is caught */
     65 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     66 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     67 
     68 
     69 extern char nullstr[1];		/* null string */
     70 
     71 char *trap[MAXSIG+1];		/* trap handler commands */
     72 MKINIT char sigmode[MAXSIG];	/* current value of signal */
     73 char gotsig[MAXSIG];		/* indicates specified signal received */
     74 int pendingsigs;			/* indicates some signal received */
     75 
     76 /*
     77  * The trap builtin.
     78  */
     79 
     80 trapcmd(argc, argv)  char **argv; {
     81 	char *action;
     82 	char **ap;
     83 	int signo;
     84 
     85 	if (argc <= 1) {
     86 		for (signo = 0 ; signo <= MAXSIG ; signo++) {
     87 			if (trap[signo] != NULL)
     88 				out1fmt("%d: %s\n", signo, trap[signo]);
     89 		}
     90 		return 0;
     91 	}
     92 	ap = argv + 1;
     93 	if (is_number(*ap))
     94 		action = NULL;
     95 	else
     96 		action = *ap++;
     97 	while (*ap) {
     98 		if ((signo = number(*ap)) < 0 || signo > MAXSIG)
     99 			error("%s: bad trap", *ap);
    100 		INTOFF;
    101 		if (action)
    102 			action = savestr(action);
    103 		if (trap[signo])
    104 			ckfree(trap[signo]);
    105 		trap[signo] = action;
    106 		if (signo != 0)
    107 			setsignal(signo);
    108 		INTON;
    109 		ap++;
    110 	}
    111 	return 0;
    112 }
    113 
    114 
    115 
    116 /*
    117  * Clear traps on a fork.
    118  */
    119 
    120 void
    121 clear_traps() {
    122 	char **tp;
    123 
    124 	for (tp = trap ; tp <= &trap[MAXSIG] ; tp++) {
    125 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    126 			INTOFF;
    127 			ckfree(*tp);
    128 			*tp = NULL;
    129 			if (tp != &trap[0])
    130 				setsignal(tp - trap);
    131 			INTON;
    132 		}
    133 	}
    134 }
    135 
    136 
    137 
    138 /*
    139  * Set the signal handler for the specified signal.  The routine figures
    140  * out what it should be set to.
    141  */
    142 
    143 int
    144 setsignal(signo) {
    145 	int action;
    146 	sig_t sigact;
    147 	char *t;
    148 	extern void onsig();
    149 
    150 	if ((t = trap[signo]) == NULL)
    151 		action = S_DFL;
    152 	else if (*t != '\0')
    153 		action = S_CATCH;
    154 	else
    155 		action = S_IGN;
    156 	if (rootshell && action == S_DFL) {
    157 		switch (signo) {
    158 		case SIGINT:
    159 			if (iflag)
    160 				action = S_CATCH;
    161 			break;
    162 		case SIGQUIT:
    163 #ifdef DEBUG
    164 			{
    165 			extern int debug;
    166 
    167 			if (debug)
    168 				break;
    169 			}
    170 #endif
    171 			/* FALLTHROUGH */
    172 		case SIGTERM:
    173 			if (iflag)
    174 				action = S_IGN;
    175 			break;
    176 #if JOBS
    177 		case SIGTSTP:
    178 		case SIGTTOU:
    179 			if (jflag)
    180 				action = S_IGN;
    181 			break;
    182 #endif
    183 		}
    184 	}
    185 	t = &sigmode[signo - 1];
    186 	if (*t == 0) {	/* current setting unknown */
    187 		/*
    188 		 * There is a race condition here if action is not S_IGN.
    189 		 * A signal can be ignored that shouldn't be.
    190 		 */
    191 		if ((int)(sigact = signal(signo, SIG_IGN)) == -1)
    192 			error("Signal system call failed");
    193 		if (sigact == SIG_IGN) {
    194 			*t = S_HARD_IGN;
    195 		} else {
    196 			*t = S_IGN;
    197 		}
    198 	}
    199 	if (*t == S_HARD_IGN || *t == action)
    200 		return 0;
    201 	switch (action) {
    202 		case S_DFL:	sigact = SIG_DFL;	break;
    203 		case S_CATCH:  	sigact = onsig;		break;
    204 		case S_IGN:	sigact = SIG_IGN;	break;
    205 	}
    206 	*t = action;
    207 	return (int)signal(signo, sigact);
    208 }
    209 
    210 
    211 /*
    212  * Ignore a signal.
    213  */
    214 
    215 void
    216 ignoresig(signo) {
    217 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    218 		signal(signo, SIG_IGN);
    219 	}
    220 	sigmode[signo - 1] = S_HARD_IGN;
    221 }
    222 
    223 
    224 #ifdef mkinit
    225 INCLUDE "signames.h"
    226 INCLUDE "trap.h"
    227 
    228 SHELLPROC {
    229 	char *sm;
    230 
    231 	clear_traps();
    232 	for (sm = sigmode ; sm < sigmode + MAXSIG ; sm++) {
    233 		if (*sm == S_IGN)
    234 			*sm = S_HARD_IGN;
    235 	}
    236 }
    237 #endif
    238 
    239 
    240 
    241 /*
    242  * Signal handler.
    243  */
    244 
    245 void
    246 onsig(signo) {
    247 	signal(signo, onsig);
    248 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    249 		onint();
    250 		return;
    251 	}
    252 	gotsig[signo - 1] = 1;
    253 	pendingsigs++;
    254 }
    255 
    256 
    257 
    258 /*
    259  * Called to execute a trap.  Perhaps we should avoid entering new trap
    260  * handlers while we are executing a trap handler.
    261  */
    262 
    263 void
    264 dotrap() {
    265 	int i;
    266 	int savestatus;
    267 
    268 	for (;;) {
    269 		for (i = 1 ; ; i++) {
    270 			if (gotsig[i - 1])
    271 				break;
    272 			if (i >= MAXSIG)
    273 				goto done;
    274 		}
    275 		gotsig[i - 1] = 0;
    276 		savestatus=exitstatus;
    277 		evalstring(trap[i]);
    278 		exitstatus=savestatus;
    279 	}
    280 done:
    281 	pendingsigs = 0;
    282 }
    283 
    284 
    285 
    286 /*
    287  * Controls whether the shell is interactive or not.
    288  */
    289 
    290 int is_interactive;
    291 
    292 void
    293 setinteractive(on) {
    294 	if (on == is_interactive)
    295 		return;
    296 	setsignal(SIGINT);
    297 	setsignal(SIGQUIT);
    298 	setsignal(SIGTERM);
    299 	is_interactive = on;
    300 }
    301 
    302 
    303 
    304 /*
    305  * Called to exit the shell.
    306  */
    307 
    308 void
    309 exitshell(status) {
    310 	struct jmploc loc1, loc2;
    311 	char *p;
    312 
    313 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    314 	if (setjmp(loc1.loc))  goto l1;
    315 	if (setjmp(loc2.loc))  goto l2;
    316 	handler = &loc1;
    317 	if ((p = trap[0]) != NULL && *p != '\0') {
    318 		trap[0] = NULL;
    319 		evalstring(p);
    320 	}
    321 l1:   handler = &loc2;			/* probably unnecessary */
    322 	flushall();
    323 #if JOBS
    324 	setjobctl(0);
    325 #endif
    326 l2:   _exit(status);
    327 }
    328