sbin/hammer/cmd_cleanup.c

   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/sbin/hammer/cmd_cleanup.c,v 1.4.2.3 2008/09/28 22:10:15 thomas Exp $
  35  */
  36 /*
  37  * Clean up a specific HAMMER filesystem or all HAMMER filesystems.
  38  *
  39  * Each filesystem is expected to have a <mount>/snapshots directory.
  40  * No cleanup will be performed on any filesystem that does not.  If
  41  * no filesystems are specified the 'df' program is run and any HAMMER
  42  * or null-mounted hammer PFS's are extracted.
  43  *
  44  * The snapshots directory may contain a config file called 'config'.  If
  45  * no config file is present one will be created with the following
  46  * defaults:
  47  *
  48  *      snapshots 1d 60d        (0d 60d for /tmp, /var/tmp, /usr/obj)
  49  *      prune     1d 5m
  50  *      reblock   1d 5m
  51  *      recopy    30d 5m
  52  *
  53  * All hammer commands create and maintain cycle files in the snapshots
  54  * directory.
  55  */
  56
  57 #include "hammer.h"
  58
  59 struct didpfs {
  60         struct didpfs *next;
  61         uuid_t          uuid;
  62 };
  63
  64 static void do_cleanup(const char *path);
  65 static int strtosecs(char *ptr);
  66 static const char *dividing_slash(const char *path);
  67 static int check_period(const char *snapshots_path, const char *cmd, int arg1,
  68                         time_t *savep);
  69 static void save_period(const char *snapshots_path, const char *cmd,
  70                         time_t savet);
  71 static int check_softlinks(const char *snapshots_path);
  72 static void cleanup_softlinks(const char *path, const char *snapshots_path,
  73                         int arg2);
  74 static int check_expired(const char *fpath, int arg2);
  75
  76 static int cleanup_snapshots(const char *path, const char *snapshots_path,
  77                               int arg1, int arg2);
  78 static int cleanup_prune(const char *path, const char *snapshots_path,
  79                               int arg1, int arg2, int snapshots_disabled);
  80 static int cleanup_reblock(const char *path, const char *snapshots_path,
  81                               int arg1, int arg2);
  82 static int cleanup_recopy(const char *path, const char *snapshots_path,
  83                               int arg1, int arg2);
  84
  85 static void runcmd(int *resp, const char *ctl, ...);
  86
  87 #define WS      " \t\r\n"
  88
  89 struct didpfs *FirstPFS;
  90
  91 void
  92 hammer_cmd_cleanup(char **av, int ac)
  93 {
  94         FILE *fp;
  95         char *ptr;
  96         char *path;
  97         char buf[256];
  98
  99         tzset();
 100         if (ac == 0) {
 101                 fp = popen("df -t hammer,null", "r");
 102                 if (fp == NULL)
 103                         errx(1, "hammer cleanup: 'df' failed");
 104                 while (fgets(buf, sizeof(buf), fp) != NULL) {
 105                         ptr = strtok(buf, WS);
 106                         if (ptr && strcmp(ptr, "Filesystem") == 0)
 107                                 continue;
 108                         if (ptr)
 109                                 ptr = strtok(NULL, WS);
 110                         if (ptr)
 111                                 ptr = strtok(NULL, WS);
 112                         if (ptr)
 113                                 ptr = strtok(NULL, WS);
 114                         if (ptr)
 115                                 ptr = strtok(NULL, WS);
 116                         if (ptr) {
 117                                 path = strtok(NULL, WS);
 118                                 if (path)
 119                                         do_cleanup(path);
 120                         }
 121                 }
 122                 fclose(fp);
 123         } else {
 124                 while (ac) {
 125                         do_cleanup(*av);
 126                         --ac;
 127                         ++av;
 128                 }
 129         }
 130 }
 131
 132 static
 133 void
 134 do_cleanup(const char *path)
 135 {
 136         struct hammer_ioc_pseudofs_rw pfs;
 137         union hammer_ioc_mrecord_any mrec_tmp;
 138         char *snapshots_path;
 139         char *config_path;
 140         struct stat st;
 141         char *cmd;
 142         char *ptr;
 143         int arg1;
 144         int arg2;
 145         time_t savet;
 146         char buf[256];
 147         FILE *fp;
 148         struct didpfs *didpfs;
 149         int snapshots_disabled = 0;
 150         int prune_warning = 0;
 151         int fd;
 152         int r;
 153
 154         bzero(&pfs, sizeof(pfs));
 155         bzero(&mrec_tmp, sizeof(mrec_tmp));
 156         pfs.ondisk = &mrec_tmp.pfs.pfsd;
 157         pfs.bytes = sizeof(mrec_tmp.pfs.pfsd);
 158         pfs.pfs_id = -1;
 159
 160         printf("cleanup %-20s -", path);
 161         fd = open(path, O_RDONLY);
 162         if (fd < 0) {
 163                 printf(" unable to access directory: %s\n", strerror(errno));
 164                 return;
 165         }
 166         if (ioctl(fd, HAMMERIOC_GET_PSEUDOFS, &pfs) != 0) {
 167                 printf(" not a HAMMER filesystem: %s\n", strerror(errno));
 168                 return;
 169         }
 170         close(fd);
 171         if (pfs.version != HAMMER_IOC_PSEUDOFS_VERSION) {
 172                 printf(" unrecognized HAMMER version\n");
 173                 return;
 174         }
 175
 176         /*
 177          * Make sure we have not already handled this PFS.  Several nullfs
 178          * mounts might alias the same PFS.
 179          */
 180         for (didpfs = FirstPFS; didpfs; didpfs = didpfs->next) {
 181                 if (bcmp(&didpfs->uuid, &mrec_tmp.pfs.pfsd.unique_uuid, sizeof(uuid_t)) == 0) {
 182                         printf(" pfs_id %d already handled\n", pfs.pfs_id);
 183                         return;
 184                 }
 185         }
 186         didpfs = malloc(sizeof(*didpfs));
 187         didpfs->next = FirstPFS;
 188         FirstPFS = didpfs;
 189         didpfs->uuid = mrec_tmp.pfs.pfsd.unique_uuid;
 190
 191         /*
 192          * Figure out where the snapshot directory is.
 193          */
 194         if (mrec_tmp.pfs.pfsd.snapshots[0] == '/') {
 195                 asprintf(&snapshots_path, "%s", mrec_tmp.pfs.pfsd.snapshots);
 196         } else if (mrec_tmp.pfs.pfsd.snapshots[0]) {
 197                 printf(" WARNING: pfs-slave's snapshots dir is not absolute\n");
 198                 return;
 199         } else if (mrec_tmp.pfs.pfsd.mirror_flags & HAMMER_PFSD_SLAVE) {
 200                 printf(" WARNING: must configure snapshot dir for PFS slave\n");
 201                 printf("\tWe suggest <fs>/var/slaves/<name> where "
 202                        "<fs> is the base HAMMER fs\n");
 203                 printf("\tContaining the slave\n");
 204                 return;
 205         } else {
 206                 asprintf(&snapshots_path,
 207                          "%s%ssnapshots", path, dividing_slash(path));
 208         }
 209
 210         /*
 211          * Create a snapshot directory if necessary, and a config file if
 212          * necessary.
 213          */
 214         if (stat(snapshots_path, &st) < 0) {
 215                 if (mkdir(snapshots_path, 0755) != 0) {
 216                         free(snapshots_path);
 217                         printf(" unable to create snapshot dir \"%s\": %s\n",
 218                                 snapshots_path, strerror(errno));
 219                         return;
 220                 }
 221         }
 222         asprintf(&config_path, "%s/config", snapshots_path);
 223         if ((fp = fopen(config_path, "r")) == NULL) {
 224                 fp = fopen(config_path, "w");
 225                 if (fp == NULL) {
 226                         printf(" cannot create %s: %s\n",
 227                                 config_path, strerror(errno));
 228                         return;
 229                 }
 230                 if (strcmp(path, "/tmp") == 0 ||
 231                     strcmp(path, "/var/tmp") == 0 ||
 232                     strcmp(path, "/usr/obj") == 0) {
 233                         fprintf(fp, "snapshots 0d 60d\n");
 234                 } else {
 235                         fprintf(fp, "snapshots 1d 60d\n");
 236                 }
 237                 fprintf(fp,
 238                         "prune     1d 5m\n"
 239                         "reblock   1d 5m\n"
 240                         "recopy    30d 10m\n");
 241                 fclose(fp);
 242                 fp = fopen(config_path, "r");
 243         }
 244         if (fp == NULL) {
 245                 printf(" cannot access %s: %s\n",
 246                        config_path, strerror(errno));
 247                 return;
 248         }
 249
 250         printf(" handle PFS #%d using %s\n", pfs.pfs_id, snapshots_path);
 251
 252         /*
 253          * Process the config file
 254          */
 255         while (fgets(buf, sizeof(buf), fp) != NULL) {
 256                 cmd = strtok(buf, WS);
 257                 arg1 = 0;
 258                 arg2 = 0;
 259                 if ((ptr = strtok(NULL, WS)) != NULL) {
 260                         arg1 = strtosecs(ptr);
 261                         if ((ptr = strtok(NULL, WS)) != NULL)
 262                                 arg2 = strtosecs(ptr);
 263                 }
 264
 265                 printf("%20s - ", cmd);
 266                 fflush(stdout);
 267
 268                 if (arg1 == 0) {
 269                         printf("disabled\n");
 270                         if (strcmp(cmd, "snapshots") == 0) {
 271                                 if (check_softlinks(snapshots_path))
 272                                         prune_warning = 1;
 273                                 else
 274                                         snapshots_disabled = 1;
 275                         }
 276                         continue;
 277                 }
 278
 279                 r = 1;
 280                 if (strcmp(cmd, "snapshots") == 0) {
 281                         if (check_period(snapshots_path, cmd, arg1, &savet)) {
 282                                 printf("run\n");
 283                                 cleanup_softlinks(path, snapshots_path, arg2);
 284                                 r = cleanup_snapshots(path, snapshots_path,
 285                                                   arg1, arg2);
 286                         } else {
 287                                 printf("skip\n");
 288                         }
 289                 } else if (strcmp(cmd, "prune") == 0) {
 290                         if (check_period(snapshots_path, cmd, arg1, &savet)) {
 291                                 if (prune_warning)
 292                                         printf("run - WARNING snapshot softlinks present "
 293                                                 "but snapshots disabled\n");
 294                                 else
 295                                         printf("run\n");
 296                                 r = cleanup_prune(path, snapshots_path,
 297                                               arg1, arg2, snapshots_disabled);
 298                         } else {
 299                                 printf("skip\n");
 300                         }
 301                 } else if (strcmp(cmd, "reblock") == 0) {
 302                         if (check_period(snapshots_path, cmd, arg1, &savet)) {
 303                                 printf("run");
 304                                 fflush(stdout);
 305                                 if (VerboseOpt)
 306                                         printf("\n");
 307                                 r = cleanup_reblock(path, snapshots_path,
 308                                                 arg1, arg2);
 309                         } else {
 310                                 printf("skip\n");
 311                         }
 312                 } else if (strcmp(cmd, "recopy") == 0) {
 313                         if (check_period(snapshots_path, cmd, arg1, &savet)) {
 314                                 printf("run");
 315                                 fflush(stdout);
 316                                 if (VerboseOpt)
 317                                         printf("\n");
 318                                 r = cleanup_recopy(path, snapshots_path,
 319                                                arg1, arg2);
 320                         } else {
 321                                 printf("skip\n");
 322                         }
 323                 } else {
 324                         printf("unknown directive\n");
 325                         r = 1;
 326                 }
 327                 if (r == 0)
 328                         save_period(snapshots_path, cmd, savet);
 329         }
 330         fclose(fp);
 331         usleep(1000);
 332 }
 333
 334 static
 335 int
 336 strtosecs(char *ptr)
 337 {
 338         int val;
 339
 340         val = strtol(ptr, &ptr, 0);
 341         switch(*ptr) {
 342         case 'd':
 343                 val *= 24;
 344                 /* fall through */
 345         case 'h':
 346                 val *= 60;
 347                 /* fall through */
 348         case 'm':
 349                 val *= 60;
 350                 /* fall through */
 351         case 's':
 352                 break;
 353         default:
 354                 errx(1, "illegal suffix converting %s\n", ptr);
 355                 break;
 356         }
 357         return(val);
 358 }
 359
 360 static const char *
 361 dividing_slash(const char *path)
 362 {
 363         int len = strlen(path);
 364         if (len && path[len-1] == '/')
 365                 return("");
 366         else
 367                 return("/");
 368 }
 369
 370 /*
 371  * Check whether the desired period has elapsed since the last successful
 372  * run.  The run may take a while and cross a boundary so we remember the
 373  * current time_t so we can save it later on.
 374  *
 375  * Periods in minutes, hours, or days are assumed to have been crossed
 376  * if the local time crosses a minute, hour, or day boundary regardless
 377  * of how close the last operation actually was.
 378  */
 379 static int
 380 check_period(const char *snapshots_path, const char *cmd, int arg1,
 381         time_t *savep)
 382 {
 383         char *check_path;
 384         struct tm tp1;
 385         struct tm tp2;
 386         FILE *fp;
 387         time_t baset, lastt;
 388         char buf[256];
 389
 390         time(savep);
 391         localtime_r(savep, &tp1);
 392
 393         /*
 394          * Retrieve the start time of the last successful operation.
 395          */
 396         asprintf(&check_path, "%s/.%s.period", snapshots_path, cmd);
 397         fp = fopen(check_path, "r");
 398         free(check_path);
 399         if (fp == NULL)
 400                 return(1);
 401         if (fgets(buf, sizeof(buf), fp) == NULL) {
 402                 fclose(fp);
 403                 return(1);
 404         }
 405         fclose(fp);
 406
 407         lastt = strtol(buf, NULL, 0);
 408         localtime_r(&lastt, &tp2);
 409
 410         /*
 411          * Normalize the times.  e.g. if asked to do something on a 1-day
 412          * interval the operation will be performed as soon as the day
 413          * turns over relative to the previous operation, even if the previous
 414          * operation ran a few seconds ago just before midnight.
 415          */
 416         if (arg1 % 60 == 0) {
 417                 tp1.tm_sec = 0;
 418                 tp2.tm_sec = 0;
 419         }
 420         if (arg1 % (60 * 60) == 0) {
 421                 tp1.tm_min = 0;
 422                 tp2.tm_min = 0;
 423         }
 424         if (arg1 % (24 * 60 * 60) == 0) {
 425                 tp1.tm_hour = 0;
 426                 tp2.tm_hour = 0;
 427         }
 428
 429         baset = mktime(&tp1);
 430         lastt = mktime(&tp2);
 431
 432 #if 0
 433         printf("%lld vs %lld\n", (long long)(baset - lastt), (long long)arg1);
 434 #endif
 435
 436         if ((int)(baset - lastt) >= arg1)
 437                 return(1);
 438         return(0);
 439 }
 440
 441 /*
 442  * Store the start time of the last successful operation.
 443  */
 444 static void
 445 save_period(const char *snapshots_path, const char *cmd,
 446                         time_t savet)
 447 {
 448         char *ocheck_path;
 449         char *ncheck_path;
 450         FILE *fp;
 451
 452         asprintf(&ocheck_path, "%s/.%s.period", snapshots_path, cmd);
 453         asprintf(&ncheck_path, "%s/.%s.period.new", snapshots_path, cmd);
 454         fp = fopen(ncheck_path, "w");
 455         fprintf(fp, "0x%08llx\n", (long long)savet);
 456         if (fclose(fp) == 0)
 457                 rename(ncheck_path, ocheck_path);
 458         remove(ncheck_path);
 459 }
 460
 461 /*
 462  * Simply count the number of softlinks in the snapshots dir
 463  */
 464 static int
 465 check_softlinks(const char *snapshots_path)
 466 {
 467         struct dirent *den;
 468         struct stat st;
 469         DIR *dir;
 470         char *fpath;
 471         int res = 0;
 472
 473         if ((dir = opendir(snapshots_path)) != NULL) {
 474                 while ((den = readdir(dir)) != NULL) {
 475                         if (den->d_name[0] == '.')
 476                                 continue;
 477                         asprintf(&fpath, "%s/%s", snapshots_path, den->d_name);
 478                         if (lstat(fpath, &st) == 0 && S_ISLNK(st.st_mode))
 479                                 ++res;
 480                         free(fpath);
 481                 }
 482                 closedir(dir);
 483         }
 484         return(res);
 485 }
 486
 487 /*
 488  * Clean up expired softlinks in the snapshots dir
 489  */
 490 static void
 491 cleanup_softlinks(const char *path __unused, const char *snapshots_path, int arg2)
 492 {
 493         struct dirent *den;
 494         struct stat st;
 495         DIR *dir;
 496         char *fpath;
 497
 498         if ((dir = opendir(snapshots_path)) != NULL) {
 499                 while ((den = readdir(dir)) != NULL) {
 500                         if (den->d_name[0] == '.')
 501                                 continue;
 502                         asprintf(&fpath, "%s/%s", snapshots_path, den->d_name);
 503                         if (lstat(fpath, &st) == 0 && S_ISLNK(st.st_mode) &&
 504                             strncmp(den->d_name, "snap-", 5) == 0) {
 505                                 if (check_expired(den->d_name, arg2)) {
 506                                         if (VerboseOpt) {
 507                                                 printf("    expire %s\n",
 508                                                         fpath);
 509                                         }
 510                                         remove(fpath);
 511                                 }
 512                         }
 513                         free(fpath);
 514                 }
 515                 closedir(dir);
 516         }
 517 }
 518
 519 /*
 520  * Take a softlink path in the form snap-yyyymmdd-hhmm and the
 521  * expiration in seconds (arg2) and return non-zero if the softlink
 522  * has expired.
 523  */
 524 static int
 525 check_expired(const char *fpath, int arg2)
 526 {
 527         struct tm tm;
 528         time_t t;
 529         int year;
 530         int month;
 531         int day;
 532         int hour;
 533         int minute;
 534         int r;
 535
 536         r = sscanf(fpath, "snap-%4d%2d%2d-%2d%2d",
 537                    &year, &month, &day, &hour, &minute);
 538         if (r == 5) {
 539                 bzero(&tm, sizeof(tm));
 540                 tm.tm_isdst = -1;
 541                 tm.tm_min = minute;
 542                 tm.tm_hour = hour;
 543                 tm.tm_mday = day;
 544                 tm.tm_mon = month - 1;
 545                 tm.tm_year = year - 1900;
 546                 t = time(NULL) - mktime(&tm);
 547                 if ((int)t > arg2)
 548                         return(1);
 549         }
 550         return(0);
 551 }
 552
 553 /*
 554  * Issue a snapshot.
 555  */
 556 static int
 557 cleanup_snapshots(const char *path __unused, const char *snapshots_path,
 558                   int arg1 __unused, int arg2 __unused)
 559 {
 560         int r;
 561
 562         runcmd(&r, "hammer snapshot %s %s", path, snapshots_path);
 563         return(r);
 564 }
 565
 566 static int
 567 cleanup_prune(const char *path __unused, const char *snapshots_path,
 568                   int arg1 __unused, int arg2, int snapshots_disabled)
 569 {
 570         /*
 571          * If snapshots have been disabled run prune-everything instead
 572          * of prune.
 573          */
 574         if (snapshots_disabled && arg2) {
 575                 runcmd(NULL, "hammer -c %s/.prune.cycle -t %d prune-everything %s",
 576                         snapshots_path, arg2, path);
 577         } else if (snapshots_disabled) {
 578                 runcmd(NULL, "hammer prune-everything %s", path);
 579         } else if (arg2) {
 580                 runcmd(NULL, "hammer -c %s/.prune.cycle -t %d prune %s",
 581                         snapshots_path, arg2, snapshots_path);
 582         } else {
 583                 runcmd(NULL, "hammer prune %s", snapshots_path);
 584         }
 585         return(0);
 586 }
 587
 588 static int
 589 cleanup_reblock(const char *path, const char *snapshots_path,
 590                   int arg1 __unused, int arg2)
 591 {
 592         if (VerboseOpt == 0) {
 593                 printf(".");
 594                 fflush(stdout);
 595         }
 596         runcmd(NULL,
 597                "hammer -c %s/.reblock-1.cycle -t %d reblock-btree %s 95",
 598                snapshots_path, arg2, path);
 599         if (VerboseOpt == 0) {
 600                 printf(".");
 601                 fflush(stdout);
 602         }
 603         runcmd(NULL,
 604                "hammer -c %s/.reblock-2.cycle -t %d reblock-inodes %s 95",
 605                snapshots_path, arg2, path);
 606         if (VerboseOpt == 0) {
 607                 printf(".");
 608                 fflush(stdout);
 609         }
 610         runcmd(NULL,
 611                "hammer -c %s/.reblock-3.cycle -t %d reblock-data %s 95",
 612                snapshots_path, arg2, path);
 613         if (VerboseOpt == 0)
 614                 printf("\n");
 615         return(0);
 616 }
 617
 618 static int
 619 cleanup_recopy(const char *path, const char *snapshots_path,
 620                   int arg1 __unused, int arg2)
 621 {
 622         if (VerboseOpt == 0) {
 623                 printf(".");
 624                 fflush(stdout);
 625         }
 626         runcmd(NULL,
 627                "hammer -c %s/.recopy-1.cycle -t %d reblock-btree %s",
 628                snapshots_path, arg2, path);
 629         if (VerboseOpt == 0) {
 630                 printf(".");
 631                 fflush(stdout);
 632         }
 633         runcmd(NULL,
 634                "hammer -c %s/.recopy-2.cycle -t %d reblock-inodes %s",
 635                snapshots_path, arg2, path);
 636         if (VerboseOpt == 0) {
 637                 printf(".");
 638                 fflush(stdout);
 639         }
 640         runcmd(NULL,
 641                "hammer -c %s/.recopy-3.cycle -t %d reblock-data %s",
 642                snapshots_path, arg2, path);
 643         if (VerboseOpt == 0)
 644                 printf("\n");
 645         return(0);
 646 }
 647
 648 static
 649 void
 650 runcmd(int *resp, const char *ctl, ...)
 651 {
 652         va_list va;
 653         char *cmd;
 654         char *arg;
 655         char **av;
 656         int n;
 657         int nmax;
 658         int res;
 659         pid_t pid;
 660
 661         /*
 662          * Generate the command
 663          */
 664         va_start(va, ctl);
 665         vasprintf(&cmd, ctl, va);
 666         va_end(va);
 667         if (VerboseOpt)
 668                 printf("    %s\n", cmd);
 669
 670         /*
 671          * Break us down into arguments.  We do not just use system() here
 672          * because it blocks SIGINT and friends.
 673          */
 674         n = 0;
 675         nmax = 16;
 676         av = malloc(sizeof(char *) * nmax);
 677
 678         for (arg = strtok(cmd, WS); arg; arg = strtok(NULL, WS)) {
 679                 if (n == nmax - 1) {
 680                         nmax += 16;
 681                         av = realloc(av, sizeof(char *) * nmax);
 682                 }
 683                 av[n++] = arg;
 684         }
 685         av[n++] = NULL;
 686
 687         /*
 688          * Run the command.
 689          */
 690         if ((pid = fork()) == 0) {
 691                 if (VerboseOpt < 2) {
 692                         int fd = open("/dev/null", O_RDWR);
 693                         dup2(fd, 1);
 694                         close(fd);
 695                 }
 696                 execvp(av[0], av);
 697                 _exit(127);
 698         } else if (pid < 0) {
 699                 res = 127;
 700         } else {
 701                 int status;
 702                 while (waitpid(pid, &status, 0) != pid)
 703                         ;
 704                 res = WEXITSTATUS(status);
 705         }
 706
 707         free(cmd);
 708         free(av);
 709         if (resp)
 710                 *resp = res;
 711 }
 712
 713