1 /* 2 * Copyright (c) 2008 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 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 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $DragonFly: src/usr.bin/undo/undo.c,v 1.6 2008/07/17 21:34:47 thomas Exp $ 35 */ 36 /* 37 * UNDO - retrieve an older version of a file. 38 */ 39 40 #include <sys/types.h> 41 #include <sys/stat.h> 42 #include <sys/wait.h> 43 #include <sys/tree.h> 44 #include <sys/param.h> 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <stdarg.h> 48 #include <string.h> 49 #include <unistd.h> 50 #include <fcntl.h> 51 #include <errno.h> 52 #include <vfs/hammer/hammer_disk.h> 53 #include <vfs/hammer/hammer_ioctl.h> 54 55 /* 56 * Sorted list of transaction ids 57 */ 58 struct undo_hist_entry; 59 RB_HEAD(undo_hist_entry_rb_tree, undo_hist_entry); 60 RB_PROTOTYPE2(undo_hist_entry_rb_tree, undo_hist_entry, rbnode, 61 undo_hist_entry_compare, hammer_tid_t); 62 63 struct undo_hist_entry { 64 RB_ENTRY(undo_hist_entry) rbnode; 65 struct hammer_ioc_hist_entry tse; 66 ino_t inum; 67 }; 68 69 enum undo_type { TYPE_FILE, TYPE_DIFF, TYPE_RDIFF, TYPE_HISTORY }; 70 enum undo_cmd { CMD_DUMP, CMD_ITERATEALL }; 71 72 #define UNDO_FLAG_MULT 0x0001 73 #define UNDO_FLAG_INOCHG 0x0002 74 #define UNDO_FLAG_SETTID1 0x0004 75 #define UNDO_FLAG_SETTID2 0x0008 76 77 static int undo_hist_entry_compare(struct undo_hist_entry *he1, 78 struct undo_hist_entry *he2); 79 static void doiterate(const char *filename, const char *outFileName, 80 const char *outFilePostfix, int flags, 81 struct hammer_ioc_hist_entry ts1, 82 struct hammer_ioc_hist_entry ts2, 83 enum undo_cmd cmd, enum undo_type type); 84 static void dogenerate(const char *filename, const char *outFileName, 85 const char *outFilePostfix, 86 int flags, int idx, enum undo_type type, 87 struct hammer_ioc_hist_entry ts1, 88 struct hammer_ioc_hist_entry ts2); 89 static void collect_history(int fd, int *error, 90 struct undo_hist_entry_rb_tree *tse_tree); 91 static void collect_dir_history(const char *filename, int *error, 92 struct undo_hist_entry_rb_tree *dir_tree); 93 static void clean_tree(struct undo_hist_entry_rb_tree *tree); 94 static hammer_tid_t parse_delta_time(const char *timeStr, int *flags, 95 int ind_flag); 96 static void runcmd(int fd, const char *cmd, ...); 97 static char *timestamp(hammer_ioc_hist_entry_t hen); 98 static void usage(void); 99 100 static int VerboseOpt; 101 102 RB_GENERATE2(undo_hist_entry_rb_tree, undo_hist_entry, rbnode, 103 undo_hist_entry_compare, hammer_tid_t, tse.tid); 104 105 106 int 107 main(int ac, char **av) 108 { 109 const char *outFileName = NULL; 110 const char *outFilePostfix = NULL; 111 enum undo_cmd cmd; 112 enum undo_type type; 113 struct hammer_ioc_hist_entry ts1; 114 struct hammer_ioc_hist_entry ts2; 115 int c; 116 int count_t; 117 int flags; 118 119 bzero(&ts1, sizeof(ts1)); 120 bzero(&ts2, sizeof(ts2)); 121 122 cmd = CMD_DUMP; 123 type = TYPE_FILE; 124 count_t = 0; 125 flags = 0; 126 127 while ((c = getopt(ac, av, "adDiuvo:t:")) != -1) { 128 switch(c) { 129 case 'd': 130 type = TYPE_DIFF; 131 break; 132 case 'D': 133 type = TYPE_RDIFF; 134 break; 135 case 'i': 136 if (type != TYPE_FILE) 137 usage(); 138 type = TYPE_HISTORY; 139 cmd = CMD_ITERATEALL; 140 break; 141 case 'a': 142 cmd = CMD_ITERATEALL; 143 break; 144 case 'u': 145 outFilePostfix = ".undo"; 146 break; 147 case 'v': 148 ++VerboseOpt; 149 break; 150 case 'o': 151 outFileName = optarg; 152 break; 153 case 't': 154 /* 155 * Parse one or two -t options. If two are specified 156 * -d is implied (but may be overridden) 157 */ 158 ++count_t; 159 if (count_t == 1) { 160 ts1.tid = parse_delta_time(optarg, &flags, 161 UNDO_FLAG_SETTID1); 162 } else if (count_t == 2) { 163 ts2.tid = parse_delta_time(optarg, &flags, 164 UNDO_FLAG_SETTID2); 165 if (type == TYPE_FILE) 166 type = TYPE_DIFF; 167 } else { 168 usage(); 169 } 170 break; 171 default: 172 usage(); 173 /* NOT REACHED */ 174 break; 175 } 176 } 177 178 /* 179 * Option validation 180 */ 181 if (outFileName && outFilePostfix) { 182 fprintf(stderr, "The -o option may not be combined with -u\n"); 183 usage(); 184 } 185 186 ac -= optind; 187 av += optind; 188 if (ac > 1) 189 flags |= UNDO_FLAG_MULT; 190 191 if (ac == 0) 192 usage(); 193 194 /* 195 * Validate the output template, if specified. 196 */ 197 if (outFileName && (flags & UNDO_FLAG_MULT)) { 198 const char *ptr = outFileName; 199 int didStr = 0; 200 201 while ((ptr = strchr(ptr, '%')) != NULL) { 202 if (ptr[1] == 's') { 203 if (didStr) { 204 fprintf(stderr, "Malformed output " 205 "template\n"); 206 usage(); 207 } 208 didStr = 1; 209 ++ptr; 210 } else if (ptr[1] != '%') { 211 fprintf(stderr, "Malformed output template\n"); 212 usage(); 213 } else { 214 ptr += 2; 215 } 216 } 217 } 218 219 while (ac) { 220 doiterate(*av, outFileName, outFilePostfix, 221 flags, ts1, ts2, cmd, type); 222 ++av; 223 --ac; 224 } 225 return(0); 226 } 227 228 /* 229 * Iterate through a file's history. If cmd == CMD_DUMP we take the 230 * next-to-last transaction id, unless another given. Otherwise if 231 * cmd == CMD_ITERATEALL we scan all transaction ids. 232 * 233 * Also iterate through the directory's history to locate other inodes that 234 * used the particular file name. 235 */ 236 static 237 void 238 doiterate(const char *filename, const char *outFileName, 239 const char *outFilePostfix, int flags, 240 struct hammer_ioc_hist_entry ts1, 241 struct hammer_ioc_hist_entry ts2, 242 enum undo_cmd cmd, enum undo_type type) 243 { 244 struct undo_hist_entry_rb_tree dir_tree; 245 struct undo_hist_entry_rb_tree tse_tree; 246 struct undo_hist_entry *tse1; 247 struct undo_hist_entry *tse2; 248 struct hammer_ioc_hist_entry tid_max; 249 struct stat sb; 250 char *path = NULL; 251 int i; 252 int fd; 253 int error; 254 255 RB_INIT(&dir_tree); 256 RB_INIT(&tse_tree); 257 258 tid_max.tid = HAMMER_MAX_TID; 259 tid_max.time32 = 0; 260 261 /* 262 * Use the directory history to locate all possible versions of 263 * the file. 264 */ 265 collect_dir_history(filename, &error, &dir_tree); 266 RB_FOREACH(tse1, undo_hist_entry_rb_tree, &dir_tree) { 267 asprintf(&path, "%s@@0x%016jx", filename, (uintmax_t)tse1->tse.tid); 268 stat(path, &sb); 269 if (sb.st_mode & S_IFIFO) { 270 fprintf(stderr, "Warning: fake transaction id 0x%016jx\n", (uintmax_t)tse1->tse.tid); 271 continue; 272 } 273 if ((fd = open(path, O_RDONLY)) > 0) { 274 collect_history(fd, &error, &tse_tree); 275 close(fd); 276 } 277 free(path); 278 } 279 if ((fd = open(filename, O_RDONLY)) > 0) { 280 collect_history(fd, &error, &tse_tree); 281 close(fd); 282 } 283 if (cmd == CMD_DUMP) { 284 if ((ts1.tid == 0 || 285 flags & (UNDO_FLAG_SETTID1|UNDO_FLAG_SETTID2)) && 286 RB_EMPTY(&tse_tree)) { 287 if ((fd = open(filename, O_RDONLY)) > 0) { 288 collect_history(fd, &error, &tse_tree); 289 close(fd); 290 } 291 } 292 /* 293 * Find entry if tid set to placeholder index 294 */ 295 if (flags & UNDO_FLAG_SETTID1){ 296 tse1 = RB_MAX(undo_hist_entry_rb_tree, &tse_tree); 297 while (tse1 && ts1.tid--) { 298 tse1 = RB_PREV(undo_hist_entry_rb_tree, 299 &tse_tree, tse1); 300 } 301 if (tse1) 302 ts1 = tse1->tse; 303 else 304 ts1.tid = 0; 305 } 306 if (flags & UNDO_FLAG_SETTID2){ 307 tse2 = RB_MAX(undo_hist_entry_rb_tree, &tse_tree); 308 while (tse2 && ts2.tid--) { 309 tse2 = RB_PREV(undo_hist_entry_rb_tree, 310 &tse_tree, tse2); 311 } 312 if (tse2) 313 ts2 = tse2->tse; 314 else 315 ts2.tid = 0; 316 } 317 318 /* 319 * Single entry, most recent prior to current 320 */ 321 if (ts1.tid == 0) { 322 tse2 = RB_MAX(undo_hist_entry_rb_tree, &tse_tree); 323 if (tse2) { 324 ts2 = tse2->tse; 325 tse1 = RB_PREV(undo_hist_entry_rb_tree, 326 &tse_tree, tse2); 327 if (tse1) 328 ts1 = tse1->tse; 329 } 330 } 331 if (ts1.tid == 0) { 332 printf("%s: No UNDO history found\n", filename); 333 } else { 334 dogenerate(filename, 335 outFileName, outFilePostfix, 336 0, 0, type, 337 ts1, ts2); 338 } 339 } else if (RB_ROOT(&tse_tree)) { 340 /* 341 * Iterate entire history 342 */ 343 printf("%s: ITERATE ENTIRE HISTORY\n", filename); 344 345 tse1 = NULL; 346 i = 0; 347 RB_FOREACH(tse2, undo_hist_entry_rb_tree, &tse_tree) { 348 if (tse1) { 349 dogenerate(filename, 350 outFileName, outFilePostfix, 351 flags, i, type, 352 tse1->tse, tse2->tse); 353 } 354 if (tse1 && tse2->inum != tse1->inum) 355 flags |= UNDO_FLAG_INOCHG; 356 else 357 flags &= ~UNDO_FLAG_INOCHG; 358 tse1 = tse2; 359 ++i; 360 } 361 /* 362 * There is no delta to print for the last pair, 363 * because they are identical. 364 */ 365 if (type != TYPE_DIFF && type != TYPE_RDIFF) { 366 dogenerate(filename, 367 outFileName, outFilePostfix, 368 flags, i, type, 369 tse1->tse, tid_max); 370 } 371 } else { 372 printf("%s: ITERATE ENTIRE HISTORY: %s\n", 373 filename, strerror(error)); 374 } 375 clean_tree(&dir_tree); 376 clean_tree(&tse_tree); 377 } 378 379 /* 380 * Generate output for a file as-of ts1 (ts1 may be 0!), if diffing then 381 * through ts2. 382 */ 383 static 384 void 385 dogenerate(const char *filename, const char *outFileName, 386 const char *outFilePostfix, 387 int flags, int idx, enum undo_type type, 388 struct hammer_ioc_hist_entry ts1, 389 struct hammer_ioc_hist_entry ts2) 390 { 391 struct stat st; 392 const char *elm; 393 char *ipath1 = NULL; 394 char *ipath2 = NULL; 395 FILE *fi; 396 FILE *fp; 397 char *buf; 398 char *path; 399 time_t t; 400 struct tm *tp; 401 char datestr[64]; 402 int n; 403 404 buf = malloc(8192); 405 406 /* 407 * Open the input file. If ts1 is 0 try to locate the most recent 408 * version of the file prior to the current version. 409 */ 410 if (ts1.tid == 0) 411 asprintf(&ipath1, "%s", filename); 412 else 413 asprintf(&ipath1, "%s@@0x%016jx", filename, (uintmax_t)ts1.tid); 414 415 if (ts2.tid == 0) 416 asprintf(&ipath2, "%s", filename); 417 else 418 asprintf(&ipath2, "%s@@0x%016jx", filename, (uintmax_t)ts2.tid); 419 420 if (lstat(ipath1, &st) < 0 && lstat(ipath2, &st) < 0) { 421 if (idx == 0 || VerboseOpt) { 422 fprintf(stderr, "Unable to access either %s or %s\n", 423 ipath1, ipath2); 424 } 425 free(ipath1); 426 free(ipath2); 427 goto done; 428 } 429 430 /* 431 * elm is the last component of the input file name 432 */ 433 if ((elm = strrchr(filename, '/')) != NULL) 434 ++elm; 435 else 436 elm = filename; 437 438 /* 439 * Where do we stuff our output? 440 */ 441 if (outFileName) { 442 if (flags & UNDO_FLAG_MULT) { 443 asprintf(&path, outFileName, elm); 444 fp = fopen(path, "w"); 445 if (fp == NULL) { 446 perror(path); 447 exit(1); 448 } 449 free(path); 450 } else { 451 fp = fopen(outFileName, "w"); 452 if (fp == NULL) { 453 perror(outFileName); 454 exit(1); 455 } 456 } 457 } else if (outFilePostfix) { 458 if (idx >= 0) { 459 asprintf(&path, "%s%s.%04d", filename, 460 outFilePostfix, idx); 461 } else { 462 asprintf(&path, "%s%s", filename, outFilePostfix); 463 } 464 fp = fopen(path, "w"); 465 if (fp == NULL) { 466 perror(path); 467 exit(1); 468 } 469 free(path); 470 } else { 471 if ((flags & UNDO_FLAG_MULT) && type == TYPE_FILE) { 472 if (idx >= 0) { 473 printf("\n>>> %s %04d 0x%016jx %s\n\n", 474 filename, idx, (uintmax_t)ts1.tid, 475 timestamp(&ts1)); 476 } else { 477 printf("\n>>> %s ---- 0x%016jx %s\n\n", 478 filename, (uintmax_t)ts1.tid, 479 timestamp(&ts1)); 480 } 481 } else if (idx >= 0 && type == TYPE_FILE) { 482 printf("\n>>> %s %04d 0x%016jx %s\n\n", 483 filename, idx, (uintmax_t)ts1.tid, 484 timestamp(&ts1)); 485 } 486 fp = stdout; 487 } 488 489 switch(type) { 490 case TYPE_FILE: 491 if ((fi = fopen(ipath1, "r")) != NULL) { 492 while ((n = fread(buf, 1, 8192, fi)) > 0) 493 fwrite(buf, 1, n, fp); 494 fclose(fi); 495 } 496 break; 497 case TYPE_DIFF: 498 printf("diff -N -r -u %s %s (to %s)\n", 499 ipath1, ipath2, timestamp(&ts2)); 500 fflush(stdout); 501 runcmd(fileno(fp), "/usr/bin/diff", "diff", "-N", "-r", "-u", ipath1, ipath2, NULL); 502 break; 503 case TYPE_RDIFF: 504 printf("diff -N -r -u %s %s\n", ipath2, ipath1); 505 fflush(stdout); 506 runcmd(fileno(fp), "/usr/bin/diff", "diff", "-N", "-r", "-u", ipath2, ipath1, NULL); 507 break; 508 case TYPE_HISTORY: 509 t = (time_t)ts1.time32; 510 tp = localtime(&t); 511 strftime(datestr, sizeof(datestr), "%d-%b-%Y %H:%M:%S", tp); 512 printf("\t0x%016jx %s", (uintmax_t)ts1.tid, datestr); 513 if (flags & UNDO_FLAG_INOCHG) 514 printf(" inode-change"); 515 if (lstat(ipath1, &st) < 0) 516 printf(" file-deleted"); 517 printf("\n"); 518 break; 519 } 520 521 if (fp != stdout) 522 fclose(fp); 523 done: 524 free(buf); 525 } 526 527 static 528 void 529 clean_tree(struct undo_hist_entry_rb_tree *tree) 530 { 531 struct undo_hist_entry *tse; 532 533 while ((tse = RB_ROOT(tree)) != NULL) { 534 RB_REMOVE(undo_hist_entry_rb_tree, tree, tse); 535 free(tse); 536 } 537 } 538 539 static 540 void 541 collect_history(int fd, int *errorp, struct undo_hist_entry_rb_tree *tse_tree) 542 { 543 struct hammer_ioc_history hist; 544 struct undo_hist_entry *tse; 545 struct stat st; 546 int istmp; 547 int i; 548 549 /* 550 * Setup 551 */ 552 bzero(&hist, sizeof(hist)); 553 hist.beg_tid = HAMMER_MIN_TID; 554 hist.end_tid = HAMMER_MAX_TID; 555 hist.head.flags |= HAMMER_IOC_HISTORY_ATKEY; 556 hist.key = 0; 557 hist.nxt_key = HAMMER_MAX_KEY; 558 559 *errorp = 0; 560 561 if (tse_tree == NULL) { 562 tse_tree = malloc(sizeof(*tse_tree)); 563 RB_INIT(tse_tree); 564 istmp = 1; 565 } else { 566 istmp = 0; 567 } 568 569 /* 570 * Save the inode so inode changes can be reported. 571 */ 572 st.st_ino = 0; 573 fstat(fd, &st); 574 575 /* 576 * Collect a unique set of transaction ids 577 */ 578 if (ioctl(fd, HAMMERIOC_GETHISTORY, &hist) < 0) { 579 *errorp = errno; 580 goto done; 581 } 582 for (;;) { 583 for (i = 0; i < hist.count; ++i) { 584 tse = malloc(sizeof(*tse)); 585 tse->tse = hist.hist_ary[i]; 586 tse->inum = st.st_ino; 587 if (RB_INSERT(undo_hist_entry_rb_tree, tse_tree, tse)) { 588 free(tse); 589 } 590 } 591 if (hist.head.flags & HAMMER_IOC_HISTORY_EOF) 592 break; 593 if (hist.head.flags & HAMMER_IOC_HISTORY_NEXT_KEY) { 594 hist.key = hist.nxt_key; 595 hist.nxt_key = HAMMER_MAX_KEY; 596 } 597 if (hist.head.flags & HAMMER_IOC_HISTORY_NEXT_TID) 598 hist.beg_tid = hist.nxt_tid; 599 if (ioctl(fd, HAMMERIOC_GETHISTORY, &hist) < 0) { 600 *errorp = errno; 601 break; 602 } 603 } 604 605 /* 606 * Cleanup 607 */ 608 done: 609 if (istmp) { 610 clean_tree(tse_tree); 611 free(tse_tree); 612 } 613 } 614 615 static 616 void 617 collect_dir_history(const char *filename, int *errorp, 618 struct undo_hist_entry_rb_tree *dir_tree) 619 { 620 char *dirname; 621 int fd; 622 int error; 623 624 *errorp = 0; 625 if (strrchr(filename, '/')) { 626 dirname = strdup(filename); 627 *strrchr(dirname, '/') = 0; 628 } else { 629 dirname = strdup("."); 630 } 631 if ((fd = open(dirname, O_RDONLY)) > 0) { 632 collect_history(fd, &error, dir_tree); 633 close(fd); 634 } 635 } 636 637 static 638 hammer_tid_t 639 parse_delta_time(const char *timeStr, int *flags, int ind_flag) 640 { 641 hammer_tid_t tid; 642 643 tid = strtoull(timeStr, NULL, 0); 644 if (timeStr[0] == '+') 645 ++timeStr; 646 if (timeStr[0] >= '0' && timeStr[0] <= '9' && timeStr[1] != 'x') 647 *flags |= ind_flag; 648 return(tid); 649 } 650 651 static void 652 runcmd(int fd, const char *cmd, ...) 653 { 654 va_list va; 655 pid_t pid; 656 char **av; 657 int ac; 658 int i; 659 660 va_start(va, cmd); 661 for (ac = 0; va_arg(va, void *) != NULL; ++ac) 662 ; 663 va_end(va); 664 665 av = malloc((ac + 1) * sizeof(char *)); 666 va_start(va, cmd); 667 for (i = 0; i < ac; ++i) 668 av[i] = va_arg(va, char *); 669 va_end(va); 670 av[i] = NULL; 671 672 if ((pid = fork()) < 0) { 673 perror("fork"); 674 exit(1); 675 } else if (pid == 0) { 676 if (fd != 1) { 677 dup2(fd, 1); 678 close(fd); 679 } 680 execv(cmd, av); 681 _exit(1); 682 } else { 683 while (waitpid(pid, NULL, 0) != pid) 684 ; 685 } 686 free(av); 687 } 688 689 /* 690 * Convert tid to timestamp. 691 */ 692 static char * 693 timestamp(hammer_ioc_hist_entry_t hen) 694 { 695 static char timebuf[64]; 696 time_t t = (time_t)hen->time32; 697 struct tm *tp; 698 699 tp = localtime(&t); 700 strftime(timebuf, sizeof(timebuf), "%d-%b-%Y %H:%M:%S", tp); 701 return(timebuf); 702 } 703 704 static 705 int 706 undo_hist_entry_compare(struct undo_hist_entry *he1, 707 struct undo_hist_entry *he2) 708 { 709 if (he1->tse.tid < he2->tse.tid) 710 return(-1); 711 if (he1->tse.tid > he2->tse.tid) 712 return(1); 713 return(0); 714 } 715 716 static void 717 usage(void) 718 { 719 fprintf(stderr, "undo [-adDiuv] [-o outfile] " 720 "[-t transaction-id] [-t transaction-id] path...\n" 721 " -a Iterate all historical segments\n" 722 " -d Forward diff\n" 723 " -D Reverse diff\n" 724 " -i Dump history transaction ids\n" 725 " -u Generate .undo files\n" 726 " -v Verbose\n" 727 " -o file Output to the specified file\n" 728 " -t TID Retrieve as of transaction-id, TID\n" 729 " (a second `-t TID' to diff two)\n" 730 " transaction ids must be prefixed with 0x, and\n" 731 " otherwise may specify an index starting at 0\n" 732 " and iterating backwards through the history.\n" 733 ); 734 exit(1); 735 } 736 737