trap.c revision 38521
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#if 0 39static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95"; 40#endif 41static const char rcsid[] = 42 "$Id: trap.c,v 1.11 1998/05/18 06:44:22 charnier Exp $"; 43#endif /* not lint */ 44 45#include <signal.h> 46#include <unistd.h> 47#include <stdlib.h> 48 49#include "shell.h" 50#include "main.h" 51#include "nodes.h" /* for other headers */ 52#include "eval.h" 53#include "jobs.h" 54#include "show.h" 55#include "options.h" 56#include "syntax.h" 57#include "output.h" 58#include "memalloc.h" 59#include "error.h" 60#include "trap.h" 61#include "mystring.h" 62 63 64/* 65 * Sigmode records the current value of the signal handlers for the various 66 * modes. A value of zero means that the current handler is not known. 67 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 68 */ 69 70#define S_DFL 1 /* default signal handling (SIG_DFL) */ 71#define S_CATCH 2 /* signal is caught */ 72#define S_IGN 3 /* signal is ignored (SIG_IGN) */ 73#define S_HARD_IGN 4 /* signal is ignored permenantly */ 74#define S_RESET 5 /* temporary - to reset a hard ignored sig */ 75 76 77MKINIT char sigmode[NSIG]; /* current value of signal */ 78int pendingsigs; /* indicates some signal received */ 79int in_dotrap = 0; /* Do we execute in a trap handler? */ 80static char *trap[NSIG]; /* trap handler commands */ 81static volatile sig_atomic_t gotsig[NSIG]; 82 /* indicates specified signal received */ 83static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 84 85static int getsigaction __P((int, sig_t *)); 86 87 88/* 89 * Map a string to a signal number. 90 */ 91static int 92sigstring_to_signum(sig) 93 char *sig; 94{ 95 96 if (is_number(sig)) { 97 int signo; 98 99 signo = atoi(sig); 100 return ((signo >= 0 && signo < NSIG) ? signo : (-1)); 101 } else if (strcasecmp(sig, "exit") == 0) { 102 return (0); 103 } else { 104 int n; 105 106 if (strncasecmp(sig, "sig", 3) == 0) 107 sig += 3; 108 for (n = 1; n < NSIG; n++) 109 if (strcasecmp(sys_signame[n], sig) == 0) 110 return (n); 111 } 112 return (-1); 113} 114 115 116/* 117 * Print a list of valid signal names. 118 */ 119static void 120printsignals() 121{ 122 int n; 123 124 for (n = 1; n < NSIG; n++) { 125 out1fmt("%s", sys_signame[n]); 126 if (n == (NSIG / 2) || n == (NSIG - 1)) 127 out1str("\n"); 128 else 129 out1c(' '); 130 } 131} 132 133 134/* 135 * The trap builtin. 136 */ 137int 138trapcmd(argc, argv) 139 int argc; 140 char **argv; 141{ 142 char *action; 143 int signo; 144 145 if (argc <= 1) { 146 for (signo = 0 ; signo < NSIG ; signo++) { 147 if (trap[signo] != NULL) 148 out1fmt("trap -- '%s' %s\n", trap[signo], 149 (signo) ? sys_signame[signo] : "exit"); 150 } 151 return 0; 152 } 153 action = NULL; 154 if (*++argv && strcmp(*argv, "--") == 0) 155 argv++; 156 if (*argv && sigstring_to_signum(*argv) == -1) { 157 if ((*argv)[0] != '-') { 158 action = *argv; 159 argv++; 160 } else if ((*argv)[1] == '\0') { 161 argv++; 162 } else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') { 163 printsignals(); 164 return 0; 165 } else { 166 error("bad option %s", *argv); 167 } 168 } 169 while (*argv) { 170 if ((signo = sigstring_to_signum(*argv)) == -1) 171 error("bad signal %s", *argv); 172 INTOFF; 173 if (action) 174 action = savestr(action); 175 if (trap[signo]) 176 ckfree(trap[signo]); 177 trap[signo] = action; 178 if (signo != 0) 179 setsignal(signo); 180 INTON; 181 argv++; 182 } 183 return 0; 184} 185 186 187/* 188 * Clear traps on a fork. 189 */ 190void 191clear_traps() 192{ 193 char **tp; 194 195 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 196 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 197 INTOFF; 198 ckfree(*tp); 199 *tp = NULL; 200 if (tp != &trap[0]) 201 setsignal(tp - trap); 202 INTON; 203 } 204 } 205} 206 207 208/* 209 * Set the signal handler for the specified signal. The routine figures 210 * out what it should be set to. 211 */ 212void 213setsignal(signo) 214 int signo; 215{ 216 int action; 217 sig_t sig, sigact = SIG_DFL; 218 char *t; 219 220 if ((t = trap[signo]) == NULL) 221 action = S_DFL; 222 else if (*t != '\0') 223 action = S_CATCH; 224 else 225 action = S_IGN; 226 if (action == S_DFL) { 227 switch (signo) { 228 case SIGINT: 229 action = S_CATCH; 230 break; 231 case SIGQUIT: 232#ifdef DEBUG 233 { 234 extern int debug; 235 236 if (debug) 237 break; 238 } 239#endif 240 action = S_IGN; 241 break; 242 case SIGTERM: 243 if (rootshell && iflag) 244 action = S_IGN; 245 break; 246#if JOBS 247 case SIGTSTP: 248 case SIGTTOU: 249 if (rootshell && mflag) 250 action = S_IGN; 251 break; 252#endif 253 } 254 } 255 256 t = &sigmode[signo]; 257 if (*t == 0) { 258 /* 259 * current setting unknown 260 */ 261 if (!getsigaction(signo, &sigact)) { 262 /* 263 * Pretend it worked; maybe we should give a warning 264 * here, but other shells don't. We don't alter 265 * sigmode, so that we retry every time. 266 */ 267 return; 268 } 269 if (sigact == SIG_IGN) { 270 if (mflag && (signo == SIGTSTP || 271 signo == SIGTTIN || signo == SIGTTOU)) { 272 *t = S_IGN; /* don't hard ignore these */ 273 } else 274 *t = S_HARD_IGN; 275 } else { 276 *t = S_RESET; /* force to be set */ 277 } 278 } 279 if (*t == S_HARD_IGN || *t == action) 280 return; 281 switch (action) { 282 case S_DFL: sigact = SIG_DFL; break; 283 case S_CATCH: sigact = onsig; break; 284 case S_IGN: sigact = SIG_IGN; break; 285 } 286 *t = action; 287 sig = signal(signo, sigact); 288#ifdef BSD 289 if (sig != SIG_ERR && action == S_CATCH) 290 siginterrupt(signo, 1); 291#endif 292} 293 294 295/* 296 * Return the current setting for sig w/o changing it. 297 */ 298static int 299getsigaction(signo, sigact) 300 int signo; 301 sig_t *sigact; 302{ 303 struct sigaction sa; 304 305 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 306 return 0; 307 *sigact = (sig_t) sa.sa_handler; 308 return 1; 309} 310 311 312/* 313 * Ignore a signal. 314 */ 315void 316ignoresig(signo) 317 int signo; 318{ 319 320 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 321 signal(signo, SIG_IGN); 322 } 323 sigmode[signo] = S_HARD_IGN; 324} 325 326 327#ifdef mkinit 328INCLUDE <signal.h> 329INCLUDE "trap.h" 330 331SHELLPROC { 332 char *sm; 333 334 clear_traps(); 335 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 336 if (*sm == S_IGN) 337 *sm = S_HARD_IGN; 338 } 339} 340#endif 341 342 343/* 344 * Signal handler. 345 */ 346void 347onsig(signo) 348 int signo; 349{ 350 351#ifndef BSD 352 signal(signo, onsig); 353#endif 354 if (signo == SIGINT && trap[SIGINT] == NULL) { 355 onint(); 356 return; 357 } 358 if (signo != SIGCHLD || !ignore_sigchld) 359 gotsig[signo] = 1; 360 pendingsigs++; 361 if (signo == SIGINT && in_waitcmd != 0) { 362 dotrap(); 363 breakwaitcmd = 1; 364 } 365} 366 367 368/* 369 * Called to execute a trap. Perhaps we should avoid entering new trap 370 * handlers while we are executing a trap handler. 371 */ 372void 373dotrap() 374{ 375 int i; 376 int savestatus; 377 378 in_dotrap++; 379 for (;;) { 380 for (i = 1; i < NSIG; i++) { 381 if (gotsig[i]) { 382 gotsig[i] = 0; 383 if (trap[i]) { 384 /* 385 * Ignore SIGCHLD to avoid infinite recursion 386 * if the trap action does a fork. 387 */ 388 if (i == SIGCHLD) 389 ignore_sigchld++; 390 savestatus = exitstatus; 391 evalstring(trap[i]); 392 exitstatus = savestatus; 393 if (i == SIGCHLD) 394 ignore_sigchld--; 395 } 396 break; 397 } 398 } 399 if (i >= NSIG) 400 break; 401 } 402 in_dotrap--; 403 pendingsigs = 0; 404} 405 406 407/* 408 * Controls whether the shell is interactive or not. 409 */ 410void 411setinteractive(on) 412 int on; 413{ 414 static int is_interactive = -1; 415 416 if (on == is_interactive) 417 return; 418 setsignal(SIGINT); 419 setsignal(SIGQUIT); 420 setsignal(SIGTERM); 421 is_interactive = on; 422} 423 424 425/* 426 * Called to exit the shell. 427 */ 428void 429exitshell(status) 430 int status; 431{ 432 struct jmploc loc1, loc2; 433 char *p; 434 435 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 436 if (setjmp(loc1.loc)) { 437 goto l1; 438 } 439 if (setjmp(loc2.loc)) { 440 goto l2; 441 } 442 handler = &loc1; 443 if ((p = trap[0]) != NULL && *p != '\0') { 444 trap[0] = NULL; 445 evalstring(p); 446 } 447l1: handler = &loc2; /* probably unnecessary */ 448 flushall(); 449#if JOBS 450 setjobctl(0); 451#endif 452l2: _exit(status); 453} 454