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trap.c revision 1.6 
      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 
     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 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     68 
     69 
     70 extern char nullstr[1];		/* null string */
     71 
     72 char *trap[MAXSIG+1];		/* trap handler commands */
     73 MKINIT char sigmode[MAXSIG];	/* current value of signal */
     74 char gotsig[MAXSIG];		/* indicates specified signal received */
     75 int pendingsigs;			/* indicates some signal received */
     76 
     77 /*
     78  * The trap builtin.
     79  */
     80 
     81 trapcmd(argc, argv)  char **argv; {
     82 	char *action;
     83 	char **ap;
     84 	int signo;
     85 
     86 	if (argc <= 1) {
     87 		for (signo = 0 ; signo <= MAXSIG ; signo++) {
     88 			if (trap[signo] != NULL)
     89 				out1fmt("%d: %s\n", signo, trap[signo]);
     90 		}
     91 		return 0;
     92 	}
     93 	ap = argv + 1;
     94 	if (is_number(*ap))
     95 		action = NULL;
     96 	else
     97 		action = *ap++;
     98 	while (*ap) {
     99 		if ((signo = number(*ap)) < 0 || signo > MAXSIG)
    100 			error("%s: bad trap", *ap);
    101 		INTOFF;
    102 		if (action)
    103 			action = savestr(action);
    104 		if (trap[signo])
    105 			ckfree(trap[signo]);
    106 		trap[signo] = action;
    107 		if (signo != 0)
    108 			setsignal(signo);
    109 		INTON;
    110 		ap++;
    111 	}
    112 	return 0;
    113 }
    114 
    115 
    116 
    117 /*
    118  * Clear traps on a fork.
    119  */
    120 
    121 void
    122 clear_traps() {
    123 	char **tp;
    124 
    125 	for (tp = trap ; tp <= &trap[MAXSIG] ; tp++) {
    126 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    127 			INTOFF;
    128 			ckfree(*tp);
    129 			*tp = NULL;
    130 			if (tp != &trap[0])
    131 				setsignal(tp - trap);
    132 			INTON;
    133 		}
    134 	}
    135 }
    136 
    137 
    138 
    139 /*
    140  * Set the signal handler for the specified signal.  The routine figures
    141  * out what it should be set to.
    142  */
    143 
    144 int
    145 setsignal(signo) {
    146 	int action;
    147 	sig_t sigact;
    148 	char *t;
    149 	extern void onsig();
    150 	extern sig_t getsigaction();
    151 
    152 	if ((t = trap[signo]) == NULL)
    153 		action = S_DFL;
    154 	else if (*t != '\0')
    155 		action = S_CATCH;
    156 	else
    157 		action = S_IGN;
    158 	if (rootshell && action == S_DFL) {
    159 		switch (signo) {
    160 		case SIGINT:
    161 			if (iflag)
    162 				action = S_CATCH;
    163 			break;
    164 		case SIGQUIT:
    165 #ifdef DEBUG
    166 			{
    167 			extern int debug;
    168 
    169 			if (debug)
    170 				break;
    171 			}
    172 #endif
    173 			/* FALLTHROUGH */
    174 		case SIGTERM:
    175 			if (iflag)
    176 				action = S_IGN;
    177 			break;
    178 #if JOBS
    179 		case SIGTSTP:
    180 		case SIGTTOU:
    181 			if (mflag)
    182 				action = S_IGN;
    183 			break;
    184 #endif
    185 		}
    186 	}
    187 	t = &sigmode[signo - 1];
    188 	if (*t == 0) {
    189 		/*
    190 		 * current setting unknown
    191 		 */
    192 		sigact = getsigaction(signo);
    193 		if (sigact == SIG_IGN) {
    194 			if (mflag && (signo == SIGTSTP ||
    195 			     signo == SIGTTIN || signo == SIGTTOU)) {
    196 				*t = S_IGN;	/* don't hard ignore these */
    197 			} else
    198 				*t = S_HARD_IGN;
    199 		} else {
    200 			*t = S_RESET;	/* force to be set */
    201 		}
    202 	}
    203 	if (*t == S_HARD_IGN || *t == action)
    204 		return 0;
    205 	switch (action) {
    206 		case S_DFL:	sigact = SIG_DFL;	break;
    207 		case S_CATCH:  	sigact = onsig;		break;
    208 		case S_IGN:	sigact = SIG_IGN;	break;
    209 	}
    210 	*t = action;
    211 	return (int)signal(signo, sigact);
    212 }
    213 
    214 /*
    215  * Return the current setting for sig w/o changing it.
    216  */
    217 sig_t
    218 getsigaction(signo) {
    219 	struct sigaction sa;
    220 
    221 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    222 		error("Sigaction system call failed");
    223 
    224 	return sa.sa_handler;
    225 }
    226 
    227 /*
    228  * Ignore a signal.
    229  */
    230 
    231 void
    232 ignoresig(signo) {
    233 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    234 		signal(signo, SIG_IGN);
    235 	}
    236 	sigmode[signo - 1] = S_HARD_IGN;
    237 }
    238 
    239 
    240 #ifdef mkinit
    241 INCLUDE "signames.h"
    242 INCLUDE "trap.h"
    243 
    244 SHELLPROC {
    245 	char *sm;
    246 
    247 	clear_traps();
    248 	for (sm = sigmode ; sm < sigmode + MAXSIG ; sm++) {
    249 		if (*sm == S_IGN)
    250 			*sm = S_HARD_IGN;
    251 	}
    252 }
    253 #endif
    254 
    255 
    256 
    257 /*
    258  * Signal handler.
    259  */
    260 
    261 void
    262 onsig(signo) {
    263 	signal(signo, onsig);
    264 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    265 		onint();
    266 		return;
    267 	}
    268 	gotsig[signo - 1] = 1;
    269 	pendingsigs++;
    270 }
    271 
    272 
    273 
    274 /*
    275  * Called to execute a trap.  Perhaps we should avoid entering new trap
    276  * handlers while we are executing a trap handler.
    277  */
    278 
    279 void
    280 dotrap() {
    281 	int i;
    282 	int savestatus;
    283 
    284 	for (;;) {
    285 		for (i = 1 ; ; i++) {
    286 			if (gotsig[i - 1])
    287 				break;
    288 			if (i >= MAXSIG)
    289 				goto done;
    290 		}
    291 		gotsig[i - 1] = 0;
    292 		savestatus=exitstatus;
    293 		evalstring(trap[i]);
    294 		exitstatus=savestatus;
    295 	}
    296 done:
    297 	pendingsigs = 0;
    298 }
    299 
    300 
    301 
    302 /*
    303  * Controls whether the shell is interactive or not.
    304  */
    305 
    306 
    307 void
    308 setinteractive(on) {
    309 	static int is_interactive;
    310 
    311 	if (on == is_interactive)
    312 		return;
    313 	setsignal(SIGINT);
    314 	setsignal(SIGQUIT);
    315 	setsignal(SIGTERM);
    316 	is_interactive = on;
    317 }
    318 
    319 
    320 
    321 /*
    322  * Called to exit the shell.
    323  */
    324 
    325 void
    326 exitshell(status) {
    327 	struct jmploc loc1, loc2;
    328 	char *p;
    329 
    330 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    331 	if (setjmp(loc1.loc)) {
    332 		goto l1;
    333 	}
    334 	if (setjmp(loc2.loc)) {
    335 		goto l2;
    336 	}
    337 	handler = &loc1;
    338 	if ((p = trap[0]) != NULL && *p != '\0') {
    339 		trap[0] = NULL;
    340 		evalstring(p);
    341 	}
    342 l1:   handler = &loc2;			/* probably unnecessary */
    343 	flushall();
    344 #if JOBS
    345 	setjobctl(0);
    346 #endif
    347 l2:   _exit(status);
    348 }
    349