shell_cmds/xargs/xargs.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * John B. Roll Jr.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $xMach: xargs.c,v 1.6 2002/02/23 05:27:47 tim Exp $
  35  */
  36
  37 #if 0
  38 #ifndef lint
  39 static const char copyright[] =
  40 "@(#) Copyright (c) 1990, 1993\n\
  41         The Regents of the University of California.  All rights reserved.\n";
  42 #endif /* not lint */
  43
  44 #ifndef lint
  45 static char sccsid[] = "@(#)xargs.c     8.1 (Berkeley) 6/6/93";
  46 #endif /* not lint */
  47 #endif
  48 #include <sys/cdefs.h>
  49 __FBSDID("$FreeBSD$");
  50
  51 #include <sys/types.h>
  52 #include <sys/wait.h>
  53 #include <sys/time.h>
  54 #include <sys/param.h>
  55 #include <sys/resource.h>
  56 #include <err.h>
  57 #include <errno.h>
  58 #include <fcntl.h>
  59 #include <langinfo.h>
  60 #include <locale.h>
  61 #include <paths.h>
  62 #include <regex.h>
  63 #include <stdio.h>
  64 #include <stdlib.h>
  65 #include <string.h>
  66 #include <unistd.h>
  67
  68 #include <libiosexec.h>
  69
  70 #include "pathnames.h"
  71
  72 #ifdef __APPLE__
  73 #include <get_compat.h>
  74 #else
  75 #define COMPAT_MODE(a,b) (1)
  76 #endif /* __APPLE__ */
  77
  78 long long       strtonum(const char*, long long, long long, const char**);
  79
  80 static void     parse_input(int, char *[]);
  81 static void     prerun(int, char *[]);
  82 static int      prompt(void);
  83 static void     run(char **);
  84 static void     usage(void);
  85 void            strnsubst(char **, const char *, const char *, size_t);
  86 static pid_t  xwait(int block, int *status);
  87 static void   xexit(const char *, const int);
  88 static void     waitchildren(const char *, int);
  89 static void   pids_init(void);
  90 static int    pids_empty(void);
  91 static int    pids_full(void);
  92 static void   pids_add(pid_t pid);
  93 static int    pids_remove(pid_t pid);
  94 static int    findslot(pid_t pid);
  95 static int    findfreeslot(void);
  96 static void   clearslot(int slot);
  97
  98 static int last_was_newline = 1;
  99 static int last_was_blank = 0;
 100
 101 static char echo[] = _PATH_ECHO;
 102 static char **av, **bxp, **ep, **endxp, **xp;
 103 static char *argp, *bbp, *ebp, *inpline, *p, *replstr;
 104 static const char *eofstr;
 105 static int count, insingle, indouble, oflag, pflag, tflag, Rflag, rval, zflag;
 106 static int cnt, Iflag, jfound, Lflag, Sflag, wasquoted, xflag;
 107 static int curprocs, maxprocs;
 108 static size_t pad9314053;
 109 static pid_t *childpids;
 110
 111 static volatile int childerr;
 112
 113 extern char **environ;
 114
 115 int
 116 main(int argc, char *argv[])
 117 {
 118         long arg_max;
 119         int ch, Jflag, nflag, nline;
 120         size_t nargs;
 121         size_t linelen;
 122         struct rlimit rl;
 123         char *endptr;
 124         const char *errstr;
 125
 126         inpline = replstr = NULL;
 127         ep = environ;
 128         eofstr = "";
 129         Jflag = nflag = 0;
 130
 131         (void)setlocale(LC_ALL, "");
 132
 133         /*
 134          * POSIX.2 limits the exec line length to ARG_MAX - 2K.  Running that
 135          * caused some E2BIG errors, so it was changed to ARG_MAX - 4K.  Given
 136          * that the smallest argument is 2 bytes in length, this means that
 137          * the number of arguments is limited to:
 138          *
 139          *       (ARG_MAX - 4K - LENGTH(utility + arguments)) / 2.
 140          *
 141          * We arbitrarily limit the number of arguments to 5000.  This is
 142          * allowed by POSIX.2 as long as the resulting minimum exec line is
 143          * at least LINE_MAX.  Realloc'ing as necessary is possible, but
 144          * probably not worthwhile.
 145          */
 146         nargs = 5000;
 147         if ((arg_max = sysconf(_SC_ARG_MAX)) == -1)
 148                 errx(1, "sysconf(_SC_ARG_MAX) failed");
 149         nline = arg_max - MAXPATHLEN; /* for argv[0] from execvp() */
 150         pad9314053 = sizeof(char *); /* reserve for string area rounding */
 151         while (*ep != NULL) {
 152                 /* 1 byte for each '\0' */
 153                 nline -= strlen(*ep++) + 1 + sizeof(*ep);
 154         }
 155         nline -= pad9314053;
 156         maxprocs = 1;
 157         while ((ch = getopt(argc, argv, "0E:I:J:L:n:oP:pR:S:s:rtx")) != -1)
 158                 switch (ch) {
 159                 case 'E':
 160                         eofstr = optarg;
 161                         break;
 162                 case 'I':
 163                         Jflag = 0;
 164                         Iflag = 1;
 165                         Lflag = 1;
 166                         replstr = optarg;
 167                         break;
 168                 case 'J':
 169                         Iflag = 0;
 170                         Jflag = 1;
 171                         replstr = optarg;
 172                         break;
 173                 case 'L':
 174                         Lflag = strtonum(optarg, 0, INT_MAX, &errstr);
 175                         if (errstr)
 176                                 errx(1, "-L %s: %s", optarg, errstr);
 177                         if (COMPAT_MODE("bin/xargs", "Unix2003")) {
 178                                 nflag = 0; /* Override */
 179                                 nargs = 5000;
 180                         }
 181                         break;
 182                 case 'n':
 183                         nflag = 1;
 184                         if ((nargs = strtol(optarg, NULL, 10)) <= 0)
 185                                 errx(1, "illegal argument count");
 186                         if (COMPAT_MODE("bin/xargs", "Unix2003")) {
 187                                 Lflag = 0; /* Override */
 188                         }
 189                         break;
 190                 case 'o':
 191                         oflag = 1;
 192                         break;
 193                 case 'P':
 194                         maxprocs = strtonum(optarg, 0, INT_MAX, &errstr);
 195                         if (errstr)
 196                                 errx(1, "-P %s: %s", optarg, errstr);
 197                         if (getrlimit(RLIMIT_NPROC, &rl) != 0)
 198                                 errx(1, "getrlimit failed");
 199                         if (maxprocs == 0 || maxprocs > rl.rlim_cur)
 200                                 maxprocs = rl.rlim_cur;
 201                         break;
 202                 case 'p':
 203                         pflag = 1;
 204                         break;
 205                 case 'R':
 206                         Rflag = strtol(optarg, &endptr, 10);
 207                         if (*endptr != '\0')
 208                                 errx(1, "replacements must be a number");
 209                         break;
 210                 case 'r':
 211                         /* GNU compatibility */
 212                         break;
 213                 case 'S':
 214                         Sflag = strtoul(optarg, &endptr, 10);
 215                         if (*endptr != '\0')
 216                                 errx(1, "replsize must be a number");
 217                         break;
 218                 case 's':
 219                         nline = strtonum(optarg, 0, INT_MAX, &errstr);
 220                         if (errstr)
 221                                 errx(1, "-s %s: %s", optarg, errstr);
 222                         pad9314053 = 0; /* assume the -s value is valid */
 223                         break;
 224                 case 't':
 225                         tflag = 1;
 226                         break;
 227                 case 'x':
 228                         xflag = 1;
 229                         break;
 230                 case '0':
 231                         zflag = 1;
 232                         break;
 233                 case '?':
 234                 default:
 235                         usage();
 236         }
 237         argc -= optind;
 238         argv += optind;
 239
 240         if (!Iflag && Rflag)
 241                 usage();
 242         if (!Iflag && Sflag)
 243                 usage();
 244         if (Iflag && !Rflag)
 245                 Rflag = 5;
 246         if (Iflag && !Sflag)
 247                 Sflag = 255;
 248         if (xflag && !nflag)
 249                 usage();
 250         if (Iflag || Lflag)
 251                 xflag = 1;
 252         if (replstr != NULL && *replstr == '\0')
 253                 errx(1, "replstr may not be empty");
 254
 255         pids_init();
 256
 257         /*
 258          * Allocate pointers for the utility name, the utility arguments,
 259          * the maximum arguments to be read from stdin and the trailing
 260          * NULL.
 261          */
 262         linelen = 1 + argc + nargs + 1;
 263         if ((av = bxp = malloc(linelen * sizeof(char *))) == NULL)
 264                 errx(1, "malloc failed");
 265
 266         /*
 267          * Use the user's name for the utility as argv[0], just like the
 268          * shell.  Echo is the default.  Set up pointers for the user's
 269          * arguments.
 270          */
 271         if (*argv == NULL)
 272                 cnt = strlen(*bxp++ = echo) + pad9314053;
 273         else {
 274                 do {
 275                         if (Jflag && strcmp(*argv, replstr) == 0) {
 276                                 char **avj;
 277                                 jfound = 1;
 278                                 argv++;
 279                                 for (avj = argv; *avj; avj++)
 280                                         cnt += strlen(*avj) + 1 + pad9314053;
 281                                 break;
 282                         }
 283                         cnt += strlen(*bxp++ = *argv) + 1 + pad9314053;
 284                 } while (*++argv != NULL);
 285         }
 286
 287         /*
 288          * Set up begin/end/traversing pointers into the array.  The -n
 289          * count doesn't include the trailing NULL pointer, so the malloc
 290          * added in an extra slot.
 291          */
 292         endxp = (xp = bxp) + nargs;
 293
 294         /*
 295          * Allocate buffer space for the arguments read from stdin and the
 296          * trailing NULL.  Buffer space is defined as the default or specified
 297          * space, minus the length of the utility name and arguments.  Set up
 298          * begin/end/traversing pointers into the array.  The -s count does
 299          * include the trailing NULL, so the malloc didn't add in an extra
 300          * slot.
 301          */
 302         nline -= cnt;
 303         if (nline <= 0)
 304                 errx(1, "insufficient space for command");
 305
 306         if ((bbp = malloc((size_t)(nline + 1))) == NULL)
 307                 errx(1, "malloc failed");
 308         ebp = (argp = p = bbp) + nline - 1;
 309         for (;;)
 310                 parse_input(argc, argv);
 311 }
 312
 313 static void
 314 parse_input(int argc, char *argv[])
 315 {
 316         int ch, foundeof;
 317         char **avj;
 318         int last_was_backslashed = 0;
 319
 320         foundeof = 0;
 321
 322         switch (ch = getchar()) {
 323         case EOF:
 324                 /* No arguments since last exec. */
 325                 if (p == bbp)
 326                         xexit(*av, rval);
 327                 goto arg1;
 328         case ' ':
 329                 last_was_blank = 1;
 330         case '\t':
 331                 /* Quotes escape tabs and spaces. */
 332                 if (insingle || indouble || zflag)
 333                         goto addch;
 334                 goto arg2;
 335         case '\0':
 336                 if (zflag) {
 337                         /*
 338                          * Increment 'count', so that nulls will be treated
 339                          * as end-of-line, as well as end-of-argument.  This
 340                          * is needed so -0 works properly with -I and -L.
 341                          */
 342                         count++;
 343                         goto arg2;
 344                 }
 345                 goto addch;
 346         case '\n':
 347                 if (zflag)
 348                         goto addch;
 349                 if (COMPAT_MODE("bin/xargs", "Unix2003")) {
 350                         if (last_was_newline) {
 351                                 /* don't count empty line */
 352                                 break;
 353                         }
 354                         if (!last_was_blank ) {
 355                                 /* only count if NOT continuation line */
 356                                 count++;
 357                         }
 358                 } else {
 359                         count++;
 360                 }
 361                 last_was_newline = 1;
 362
 363                 /* Quotes do not escape newlines. */
 364 arg1:           if (insingle || indouble) {
 365                         warnx("unterminated quote");
 366                         xexit(*av, 1);
 367                 }
 368 arg2:
 369                 foundeof = *eofstr != '\0' &&
 370                     strncmp(argp, eofstr, p - argp) == 0;
 371
 372 #ifdef __APPLE__
 373                 /* 6591323: -I specifies that it processes the entire line,
 374                  * so only recognize eofstr at the end of a line. */
 375                 if (Iflag && !last_was_newline)
 376                         foundeof = 0;
 377
 378                 /* 6591323: Essentially the same as the EOF handling above. */
 379                 if (foundeof && (p - strlen(eofstr) == bbp)) {
 380                         waitchildren(*argv, 1);
 381                         exit(rval);
 382                 }
 383 #endif
 384
 385                 /* Do not make empty args unless they are quoted */
 386                 if ((argp != p || wasquoted) && !foundeof) {
 387                         *p++ = '\0';
 388                         *xp++ = argp;
 389                         if (Iflag) {
 390                                 size_t curlen;
 391
 392                                 if (inpline == NULL)
 393                                         curlen = 0;
 394                                 else {
 395                                         /*
 396                                          * If this string is not zero
 397                                          * length, append a space for
 398                                          * separation before the next
 399                                          * argument.
 400                                          */
 401                                         if ((curlen = strlen(inpline)))
 402                                                 strcat(inpline, " ");
 403                                 }
 404                                 curlen++;
 405                                 /*
 406                                  * Allocate enough to hold what we will
 407                                  * be holding in a second, and to append
 408                                  * a space next time through, if we have
 409                                  * to.
 410                                  */
 411                                 inpline = realloc(inpline, curlen + 2 +
 412                                     strlen(argp));
 413                                 if (inpline == NULL) {
 414                                         warnx("realloc failed");
 415                                         xexit(*av, 1);
 416                                 }
 417                                 if (curlen == 1)
 418                                         strcpy(inpline, argp);
 419                                 else
 420                                         strcat(inpline, argp);
 421                         }
 422                 }
 423
 424                 /*
 425                  * If max'd out on args or buffer, or reached EOF,
 426                  * run the command.  If xflag and max'd out on buffer
 427                  * but not on args, object.  Having reached the limit
 428                  * of input lines, as specified by -L is the same as
 429                  * maxing out on arguments.
 430                  */
 431                 if (xp == endxp || p + (count * pad9314053) > ebp || ch == EOF ||
 432                     (Lflag <= count && xflag) || foundeof) {
 433                         if (xflag && xp != endxp && p + (count * pad9314053) > ebp) {
 434                                 warnx("insufficient space for arguments");
 435                                 xexit(*av, 1);
 436                         }
 437                         if (jfound) {
 438                                 for (avj = argv; *avj; avj++)
 439                                         *xp++ = *avj;
 440                         }
 441                         prerun(argc, av);
 442                         if (ch == EOF || foundeof)
 443                                 xexit(*av, rval);
 444                         p = bbp;
 445                         xp = bxp;
 446                         count = 0;
 447                 }
 448                 argp = p;
 449                 wasquoted = 0;
 450                 break;
 451         case '\'':
 452                 if (indouble || zflag)
 453                         goto addch;
 454                 insingle = !insingle;
 455                 wasquoted = 1;
 456                 break;
 457         case '"':
 458                 if (insingle || zflag)
 459                         goto addch;
 460                 indouble = !indouble;
 461                 wasquoted = 1;
 462                 break;
 463         case '\\':
 464                 last_was_backslashed = 1;
 465                 if (zflag)
 466                         goto addch;
 467                 /* Backslash escapes anything, is escaped by quotes. */
 468                 if (!insingle && !indouble && (ch = getchar()) == EOF) {
 469                         warnx("backslash at EOF");
 470                         xexit(*av, 1);
 471                 }
 472                 /* FALLTHROUGH */
 473         default:
 474 addch:          if (p < ebp) {
 475                         *p++ = ch;
 476                         break;
 477                 }
 478
 479                 /* If only one argument, not enough buffer space. */
 480                 if (bxp == xp) {
 481                         warnx("insufficient space for argument");
 482                         xexit(*av, 1);
 483                 }
 484                 /* Didn't hit argument limit, so if xflag object. */
 485                 if (xflag) {
 486                         warnx("insufficient space for arguments");
 487                         xexit(*av, 1);
 488                 }
 489
 490                 if (jfound) {
 491                         for (avj = argv; *avj; avj++)
 492                                 *xp++ = *avj;
 493                 }
 494                 prerun(argc, av);
 495                 xp = bxp;
 496                 cnt = ebp - argp;
 497                 memcpy(bbp, argp, (size_t)cnt);
 498                 p = (argp = bbp) + cnt;
 499                 *p++ = ch;
 500                 break;
 501         }
 502         if (ch != ' ')
 503                 last_was_blank = 0;
 504         if (ch != '\n' || last_was_backslashed)
 505                 last_was_newline = 0;
 506 }
 507
 508 /*
 509  * Do things necessary before run()'ing, such as -I substitution,
 510  * and then call run().
 511  */
 512 static void
 513 prerun(int argc, char *argv[])
 514 {
 515         char **tmp, **tmp2, **avj;
 516         int repls;
 517
 518         repls = Rflag;
 519
 520         if (argc == 0 || repls == 0) {
 521                 *xp = NULL;
 522                 run(argv);
 523                 return;
 524         }
 525
 526         avj = argv;
 527
 528         /*
 529          * Allocate memory to hold the argument list, and
 530          * a NULL at the tail.
 531          */
 532         tmp = malloc((argc + 1) * sizeof(char *));
 533         if (tmp == NULL) {
 534                 warnx("malloc failed");
 535                 xexit(*argv, 1);
 536         }
 537         tmp2 = tmp;
 538
 539         /*
 540          * Save the first argument and iterate over it, we
 541          * cannot do strnsubst() to it.
 542          */
 543         if ((*tmp++ = strdup(*avj++)) == NULL) {
 544                 warnx("strdup failed");
 545                 xexit(*argv, 1);
 546         }
 547
 548         /*
 549          * For each argument to utility, if we have not used up
 550          * the number of replacements we are allowed to do, and
 551          * if the argument contains at least one occurrence of
 552          * replstr, call strnsubst(), else just save the string.
 553          * Iterations over elements of avj and tmp are done
 554          * where appropriate.
 555          */
 556         while (--argc) {
 557                 *tmp = *avj++;
 558                 if (repls && strstr(*tmp, replstr) != NULL) {
 559                         strnsubst(tmp++, replstr, inpline, (size_t)Sflag);
 560                         if (repls > 0)
 561                                 repls--;
 562                 } else {
 563                         if ((*tmp = strdup(*tmp)) == NULL) {
 564                                 warnx("strdup failed");
 565                                 xexit(*argv, 1);
 566                         }
 567                         tmp++;
 568                 }
 569         }
 570
 571         /*
 572          * Run it.
 573          */
 574         *tmp = NULL;
 575         run(tmp2);
 576
 577         /*
 578          * Walk from the tail to the head, free along the way.
 579          */
 580         for (; tmp2 != tmp; tmp--)
 581                 free(*tmp);
 582         /*
 583          * Now free the list itself.
 584          */
 585         free(tmp2);
 586
 587         /*
 588          * Free the input line buffer, if we have one.
 589          */
 590         if (inpline != NULL) {
 591                 free(inpline);
 592                 inpline = NULL;
 593         }
 594 }
 595
 596 static void
 597 run(char **argv)
 598 {
 599         pid_t pid;
 600         int fd;
 601         char **avec;
 602
 603         /*
 604          * If the user wants to be notified of each command before it is
 605          * executed, notify them.  If they want the notification to be
 606          * followed by a prompt, then prompt them.
 607          */
 608         if (tflag || pflag) {
 609                 (void)fprintf(stderr, "%s", *argv);
 610                 for (avec = argv + 1; *avec != NULL; ++avec)
 611                         (void)fprintf(stderr, " %s", *avec);
 612                 /*
 613                  * If the user has asked to be prompted, do so.
 614                  */
 615                 if (pflag)
 616                         /*
 617                          * If they asked not to exec, return without execution
 618                          * but if they asked to, go to the execution.  If we
 619                          * could not open their tty, break the switch and drop
 620                          * back to -t behaviour.
 621                          */
 622                         switch (prompt()) {
 623                         case 0:
 624                                 return;
 625                         case 1:
 626                                 goto exec;
 627                         case 2:
 628                                 break;
 629                         }
 630                 (void)fprintf(stderr, "\n");
 631                 (void)fflush(stderr);
 632         }
 633 exec:
 634         childerr = 0;
 635         switch (pid = vfork()) {
 636         case -1:
 637                 warn("vfork");
 638                 xexit(*argv, 1);
 639         case 0:
 640                 if (oflag) {
 641                         if ((fd = open(_PATH_TTY, O_RDONLY)) == -1)
 642                                 err(1, "can't open /dev/tty");
 643                 } else {
 644                         fd = open(_PATH_DEVNULL, O_RDONLY);
 645                 }
 646                 if (fd > STDIN_FILENO) {
 647                         if (dup2(fd, STDIN_FILENO) != 0)
 648                                 err(1, "can't dup2 to stdin");
 649                         close(fd);
 650                 }
 651                 execvp(argv[0], argv);
 652                 childerr = errno;
 653                 _exit(1);
 654         }
 655         pids_add(pid);
 656         waitchildren(*argv, 0);
 657 }
 658
 659 /*
 660  * Wait for a tracked child to exit and return its pid and exit status.
 661  *
 662  * Ignores (discards) all untracked child processes.
 663  * Returns -1 and sets errno to ECHILD if no tracked children exist.
 664  * If block is set, waits indefinitely for a child process to exit.
 665  * If block is not set and no children have exited, returns 0 immediately.
 666  */
 667 static pid_t
 668 xwait(int block, int *status) {
 669         pid_t pid;
 670
 671         if (pids_empty()) {
 672                 errno = ECHILD;
 673                 return (-1);
 674         }
 675
 676         while ((pid = waitpid(-1, status, block ? 0 : WNOHANG)) > 0)
 677                 if (pids_remove(pid))
 678                         break;
 679
 680         return (pid);
 681 }
 682
 683 static void
 684 xexit(const char *name, const int exit_code) {
 685         waitchildren(name, 1);
 686         exit(exit_code);
 687 }
 688
 689 static void
 690 waitchildren(const char *name, int waitall)
 691 {
 692         pid_t pid;
 693         int status;
 694         int cause_exit = 0;
 695
 696         while ((pid = xwait(waitall || pids_full(), &status)) > 0) {
 697                 /*
 698                  * If we couldn't invoke the utility or if utility exited
 699                  * because of a signal or with a value of 255, warn (per
 700                  * POSIX), and then wait until all other children have
 701                  * exited before exiting 1-125. POSIX requires us to stop
 702                  * reading if child exits because of a signal or with 255,
 703                  * but it does not require us to exit immediately; waiting
 704                  * is preferable to orphaning.
 705                  */
 706                 if (childerr != 0 && cause_exit == 0) {
 707                         errno = childerr;
 708                         waitall = 1;
 709                         cause_exit = errno == ENOENT ? 127 : 126;
 710                         warn("%s", name);
 711                 } else if (WIFSIGNALED(status)) {
 712                         waitall = cause_exit = 1;
 713                         warnx("%s: terminated with signal %d; aborting",
 714                             name, WTERMSIG(status));
 715                 } else if (WEXITSTATUS(status) == 255) {
 716                         waitall = cause_exit = 1;
 717                         warnx("%s: exited with status 255; aborting", name);
 718                 } else if (WEXITSTATUS(status))
 719                         rval = 1;
 720         }
 721
 722         if (cause_exit)
 723                 exit(cause_exit);
 724         if (pid == -1 && errno != ECHILD)
 725                 err(1, "waitpid");
 726 }
 727
 728 #define NOPID   (0)
 729
 730 static void
 731 pids_init(void)
 732 {
 733         int i;
 734
 735         if ((childpids = malloc(maxprocs * sizeof(*childpids))) == NULL)
 736                 errx(1, "malloc failed");
 737
 738         for (i = 0; i < maxprocs; i++)
 739                 clearslot(i);
 740 }
 741
 742 static int
 743 pids_empty(void)
 744 {
 745
 746         return (curprocs == 0);
 747 }
 748
 749 static int
 750 pids_full(void)
 751 {
 752
 753         return (curprocs >= maxprocs);
 754 }
 755
 756 static void
 757 pids_add(pid_t pid)
 758 {
 759         int slot;
 760
 761         slot = findfreeslot();
 762         childpids[slot] = pid;
 763         curprocs++;
 764 }
 765
 766 static int
 767 pids_remove(pid_t pid)
 768 {
 769         int slot;
 770
 771         if ((slot = findslot(pid)) < 0)
 772                 return (0);
 773
 774         clearslot(slot);
 775         curprocs--;
 776         return (1);
 777 }
 778
 779 static int
 780 findfreeslot(void)
 781 {
 782         int slot;
 783
 784         if ((slot = findslot(NOPID)) < 0)
 785                 errx(1, "internal error: no free pid slot");
 786         return (slot);
 787 }
 788
 789 static int
 790 findslot(pid_t pid)
 791 {
 792         int slot;
 793
 794         for (slot = 0; slot < maxprocs; slot++)
 795                 if (childpids[slot] == pid)
 796                         return (slot);
 797         return (-1);
 798 }
 799
 800 static void
 801 clearslot(int slot)
 802 {
 803
 804         childpids[slot] = NOPID;
 805 }
 806
 807 /*
 808  * Prompt the user about running a command.
 809  */
 810 static int
 811 prompt(void)
 812 {
 813         regex_t cre;
 814         size_t rsize;
 815         int match;
 816         char *response;
 817         FILE *ttyfp;
 818
 819         if ((ttyfp = fopen(_PATH_TTY, "r")) == NULL)
 820                 return (2);     /* Indicate that the TTY failed to open. */
 821         (void)fprintf(stderr, "?...");
 822         (void)fflush(stderr);
 823         if ((response = fgetln(ttyfp, &rsize)) == NULL ||
 824             regcomp(&cre, nl_langinfo(YESEXPR), REG_BASIC) != 0) {
 825                 (void)fclose(ttyfp);
 826                 return (0);
 827         }
 828         response[rsize - 1] = '\0';
 829         match = regexec(&cre, response, 0, NULL, 0);
 830         (void)fclose(ttyfp);
 831         regfree(&cre);
 832         return (match == 0);
 833 }
 834
 835 static void
 836 usage(void)
 837 {
 838
 839         fprintf(stderr,
 840 "usage: xargs [-0opt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]]\n"
 841 "             [-J replstr] [-L number] [-n number [-x]] [-P maxprocs]\n"
 842 "             [-s size] [utility [argument ...]]\n");
 843         exit(1);
 844 }