ex/ex_argv.c

   1 /*-
   2  * Copyright (c) 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1993, 1994, 1995, 1996
   5  *      Keith Bostic.  All rights reserved.
   6  *
   7  * See the LICENSE file for redistribution information.
   8  */
   9
  10 #include "config.h"
  11
  12 #ifndef lint
  13 static const char sccsid[] = "$Id: ex_argv.c,v 10.28 1996/12/17 14:50:33 bostic Exp $ (Berkeley) $Date: 1996/12/17 14:50:33 $";
  14 #endif /* not lint */
  15
  16 #include <sys/types.h>
  17 #include <sys/queue.h>
  18
  19 #include <bitstring.h>
  20 #include <ctype.h>
  21 #include <dirent.h>
  22 #include <errno.h>
  23 #include <limits.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 #include "../common/common.h"
  30
  31 static int argv_alloc __P((SCR *, size_t));
  32 static int argv_comp __P((const void *, const void *));
  33 static int argv_fexp __P((SCR *, EXCMD *,
  34         char *, size_t, char *, size_t *, char **, size_t *, int));
  35 static int argv_lexp __P((SCR *, EXCMD *, char *));
  36 static int argv_sexp __P((SCR *, char **, size_t *, size_t *));
  37
  38 /*
  39  * argv_init --
  40  *      Build  a prototype arguments list.
  41  *
  42  * PUBLIC: int argv_init __P((SCR *, EXCMD *));
  43  */
  44 int
  45 argv_init(sp, excp)
  46         SCR *sp;
  47         EXCMD *excp;
  48 {
  49         EX_PRIVATE *exp;
  50
  51         exp = EXP(sp);
  52         exp->argsoff = 0;
  53         argv_alloc(sp, 1);
  54
  55         excp->argv = exp->args;
  56         excp->argc = exp->argsoff;
  57         return (0);
  58 }
  59
  60 /*
  61  * argv_exp0 --
  62  *      Append a string to the argument list.
  63  *
  64  * PUBLIC: int argv_exp0 __P((SCR *, EXCMD *, char *, size_t));
  65  */
  66 int
  67 argv_exp0(sp, excp, cmd, cmdlen)
  68         SCR *sp;
  69         EXCMD *excp;
  70         char *cmd;
  71         size_t cmdlen;
  72 {
  73         EX_PRIVATE *exp;
  74
  75         exp = EXP(sp);
  76         argv_alloc(sp, cmdlen);
  77         memcpy(exp->args[exp->argsoff]->bp, cmd, cmdlen);
  78         exp->args[exp->argsoff]->bp[cmdlen] = '\0';
  79         exp->args[exp->argsoff]->len = cmdlen;
  80         ++exp->argsoff;
  81         excp->argv = exp->args;
  82         excp->argc = exp->argsoff;
  83         return (0);
  84 }
  85
  86 /*
  87  * argv_exp1 --
  88  *      Do file name expansion on a string, and append it to the
  89  *      argument list.
  90  *
  91  * PUBLIC: int argv_exp1 __P((SCR *, EXCMD *, char *, size_t, int));
  92  */
  93 int
  94 argv_exp1(sp, excp, cmd, cmdlen, is_bang)
  95         SCR *sp;
  96         EXCMD *excp;
  97         char *cmd;
  98         size_t cmdlen;
  99         int is_bang;
 100 {
 101         EX_PRIVATE *exp;
 102         size_t blen, len;
 103         char *bp, *p, *t;
 104
 105         GET_SPACE_RET(sp, bp, blen, 512);
 106
 107         len = 0;
 108         exp = EXP(sp);
 109         if (argv_fexp(sp, excp, cmd, cmdlen, bp, &len, &bp, &blen, is_bang)) {
 110                 FREE_SPACE(sp, bp, blen);
 111                 return (1);
 112         }
 113
 114         /* If it's empty, we're done. */
 115         if (len != 0) {
 116                 for (p = bp, t = bp + len; p < t; ++p)
 117                         if (!isblank(*p))
 118                                 break;
 119                 if (p == t)
 120                         goto ret;
 121         } else
 122                 goto ret;
 123
 124         (void)argv_exp0(sp, excp, bp, len);
 125
 126 ret:    FREE_SPACE(sp, bp, blen);
 127         return (0);
 128 }
 129
 130 /*
 131  * argv_exp2 --
 132  *      Do file name and shell expansion on a string, and append it to
 133  *      the argument list.
 134  *
 135  * PUBLIC: int argv_exp2 __P((SCR *, EXCMD *, char *, size_t));
 136  */
 137 int
 138 argv_exp2(sp, excp, cmd, cmdlen)
 139         SCR *sp;
 140         EXCMD *excp;
 141         char *cmd;
 142         size_t cmdlen;
 143 {
 144         size_t blen, len, n;
 145         int rval;
 146         char *bp, *mp, *p;
 147
 148         GET_SPACE_RET(sp, bp, blen, 512);
 149
 150 #define SHELLECHO       "echo "
 151 #define SHELLOFFSET     (sizeof(SHELLECHO) - 1)
 152         memcpy(bp, SHELLECHO, SHELLOFFSET);
 153         p = bp + SHELLOFFSET;
 154         len = SHELLOFFSET;
 155
 156 #if defined(DEBUG) && 0
 157         vtrace(sp, "file_argv: {%.*s}\n", (int)cmdlen, cmd);
 158 #endif
 159
 160         if (argv_fexp(sp, excp, cmd, cmdlen, p, &len, &bp, &blen, 0)) {
 161                 rval = 1;
 162                 goto err;
 163         }
 164
 165 #if defined(DEBUG) && 0
 166         vtrace(sp, "before shell: %d: {%s}\n", len, bp);
 167 #endif
 168
 169         /*
 170          * Do shell word expansion -- it's very, very hard to figure out what
 171          * magic characters the user's shell expects.  Historically, it was a
 172          * union of v7 shell and csh meta characters.  We match that practice
 173          * by default, so ":read \%" tries to read a file named '%'.  It would
 174          * make more sense to pass any special characters through the shell,
 175          * but then, if your shell was csh, the above example will behave
 176          * differently in nvi than in vi.  If you want to get other characters
 177          * passed through to your shell, change the "meta" option.
 178          *
 179          * To avoid a function call per character, we do a first pass through
 180          * the meta characters looking for characters that aren't expected
 181          * to be there, and then we can ignore them in the user's argument.
 182          */
 183         if (opts_empty(sp, O_SHELL, 1) || opts_empty(sp, O_SHELLMETA, 1))
 184                 n = 0;
 185         else {
 186                 for (p = mp = O_STR(sp, O_SHELLMETA); *p != '\0'; ++p)
 187                         if (isblank(*p) || isalnum(*p))
 188                                 break;
 189                 p = bp + SHELLOFFSET;
 190                 n = len - SHELLOFFSET;
 191                 if (*p != '\0') {
 192                         for (; n > 0; --n, ++p)
 193                                 if (strchr(mp, *p) != NULL)
 194                                         break;
 195                 } else
 196                         for (; n > 0; --n, ++p)
 197                                 if (!isblank(*p) &&
 198                                     !isalnum(*p) && strchr(mp, *p) != NULL)
 199                                         break;
 200         }
 201
 202         /*
 203          * If we found a meta character in the string, fork a shell to expand
 204          * it.  Unfortunately, this is comparatively slow.  Historically, it
 205          * didn't matter much, since users don't enter meta characters as part
 206          * of pathnames that frequently.  The addition of filename completion
 207          * broke that assumption because it's easy to use.  As a result, lots
 208          * folks have complained that the expansion code is too slow.  So, we
 209          * detect filename completion as a special case, and do it internally.
 210          * Note that this code assumes that the <asterisk> character is the
 211          * match-anything meta character.  That feels safe -- if anyone writes
 212          * a shell that doesn't follow that convention, I'd suggest giving them
 213          * a festive hot-lead enema.
 214          */
 215         switch (n) {
 216         case 0:
 217                 p = bp + SHELLOFFSET;
 218                 len -= SHELLOFFSET;
 219                 rval = argv_exp3(sp, excp, p, len);
 220                 break;
 221         case 1:
 222                 if (*p == '*') {
 223                         *p = '\0';
 224                         rval = argv_lexp(sp, excp, bp + SHELLOFFSET);
 225                         break;
 226                 }
 227                 /* FALLTHROUGH */
 228         default:
 229                 if (argv_sexp(sp, &bp, &blen, &len)) {
 230                         rval = 1;
 231                         goto err;
 232                 }
 233                 p = bp;
 234                 rval = argv_exp3(sp, excp, p, len);
 235                 break;
 236         }
 237
 238 err:    FREE_SPACE(sp, bp, blen);
 239         return (rval);
 240 }
 241
 242 /*
 243  * argv_exp3 --
 244  *      Take a string and break it up into an argv, which is appended
 245  *      to the argument list.
 246  *
 247  * PUBLIC: int argv_exp3 __P((SCR *, EXCMD *, char *, size_t));
 248  */
 249 int
 250 argv_exp3(sp, excp, cmd, cmdlen)
 251         SCR *sp;
 252         EXCMD *excp;
 253         char *cmd;
 254         size_t cmdlen;
 255 {
 256         EX_PRIVATE *exp;
 257         size_t len;
 258         int ch, off;
 259         char *ap, *p;
 260
 261         for (exp = EXP(sp); cmdlen > 0; ++exp->argsoff) {
 262                 /* Skip any leading whitespace. */
 263                 for (; cmdlen > 0; --cmdlen, ++cmd) {
 264                         ch = *cmd;
 265                         if (!isblank(ch))
 266                                 break;
 267                 }
 268                 if (cmdlen == 0)
 269                         break;
 270
 271                 /*
 272                  * Determine the length of this whitespace delimited
 273                  * argument.
 274                  *
 275                  * QUOTING NOTE:
 276                  *
 277                  * Skip any character preceded by the user's quoting
 278                  * character.
 279                  */
 280                 for (ap = cmd, len = 0; cmdlen > 0; ++cmd, --cmdlen, ++len) {
 281                         ch = *cmd;
 282                         if (IS_ESCAPE(sp, excp, ch) && cmdlen > 1) {
 283                                 ++cmd;
 284                                 --cmdlen;
 285                         } else if (isblank(ch))
 286                                 break;
 287                 }
 288
 289                 /*
 290                  * Copy the argument into place.
 291                  *
 292                  * QUOTING NOTE:
 293                  *
 294                  * Lose quote chars.
 295                  */
 296                 argv_alloc(sp, len);
 297                 off = exp->argsoff;
 298                 exp->args[off]->len = len;
 299                 for (p = exp->args[off]->bp; len > 0; --len, *p++ = *ap++)
 300                         if (IS_ESCAPE(sp, excp, *ap))
 301                                 ++ap;
 302                 *p = '\0';
 303         }
 304         excp->argv = exp->args;
 305         excp->argc = exp->argsoff;
 306
 307 #if defined(DEBUG) && 0
 308         for (cnt = 0; cnt < exp->argsoff; ++cnt)
 309                 vtrace(sp, "arg %d: {%s}\n", cnt, exp->argv[cnt]);
 310 #endif
 311         return (0);
 312 }
 313
 314 /*
 315  * argv_fexp --
 316  *      Do file name and bang command expansion.
 317  */
 318 static int
 319 argv_fexp(sp, excp, cmd, cmdlen, p, lenp, bpp, blenp, is_bang)
 320         SCR *sp;
 321         EXCMD *excp;
 322         char *cmd, *p, **bpp;
 323         size_t cmdlen, *lenp, *blenp;
 324         int is_bang;
 325 {
 326         EX_PRIVATE *exp;
 327         char *bp, *t;
 328         size_t blen, len, off, tlen;
 329
 330         /* Replace file name characters. */
 331         for (bp = *bpp, blen = *blenp, len = *lenp; cmdlen > 0; --cmdlen, ++cmd)
 332                 switch (*cmd) {
 333                 case '!':
 334                         if (!is_bang)
 335                                 goto ins_ch;
 336                         exp = EXP(sp);
 337                         if (exp->lastbcomm == NULL) {
 338                                 msgq(sp, M_ERR,
 339                                     "115|No previous command to replace \"!\"");
 340                                 return (1);
 341                         }
 342                         len += tlen = strlen(exp->lastbcomm);
 343                         off = p - bp;
 344                         ADD_SPACE_RET(sp, bp, blen, len);
 345                         p = bp + off;
 346                         memcpy(p, exp->lastbcomm, tlen);
 347                         p += tlen;
 348                         F_SET(excp, E_MODIFY);
 349                         break;
 350                 case '%':
 351                         if ((t = sp->frp->name) == NULL) {
 352                                 msgq(sp, M_ERR,
 353                                     "116|No filename to substitute for %%");
 354                                 return (1);
 355                         }
 356                         tlen = strlen(t);
 357                         len += tlen;
 358                         off = p - bp;
 359                         ADD_SPACE_RET(sp, bp, blen, len);
 360                         p = bp + off;
 361                         memcpy(p, t, tlen);
 362                         p += tlen;
 363                         F_SET(excp, E_MODIFY);
 364                         break;
 365                 case '#':
 366                         if ((t = sp->alt_name) == NULL) {
 367                                 msgq(sp, M_ERR,
 368                                     "117|No filename to substitute for #");
 369                                 return (1);
 370                         }
 371                         len += tlen = strlen(t);
 372                         off = p - bp;
 373                         ADD_SPACE_RET(sp, bp, blen, len);
 374                         p = bp + off;
 375                         memcpy(p, t, tlen);
 376                         p += tlen;
 377                         F_SET(excp, E_MODIFY);
 378                         break;
 379                 case '\\':
 380                         /*
 381                          * QUOTING NOTE:
 382                          *
 383                          * Strip any backslashes that protected the file
 384                          * expansion characters.
 385                          */
 386                         if (cmdlen > 1 &&
 387                             (cmd[1] == '%' || cmd[1] == '#' || cmd[1] == '!')) {
 388                                 ++cmd;
 389                                 --cmdlen;
 390                         }
 391                         /* FALLTHROUGH */
 392                 default:
 393 ins_ch:                 ++len;
 394                         off = p - bp;
 395                         ADD_SPACE_RET(sp, bp, blen, len);
 396                         p = bp + off;
 397                         *p++ = *cmd;
 398                 }
 399
 400         /* Nul termination. */
 401         ++len;
 402         off = p - bp;
 403         ADD_SPACE_RET(sp, bp, blen, len);
 404         p = bp + off;
 405         *p = '\0';
 406
 407         /* Return the new string length, buffer, buffer length. */
 408         *lenp = len - 1;
 409         *bpp = bp;
 410         *blenp = blen;
 411         return (0);
 412 }
 413
 414 /*
 415  * argv_alloc --
 416  *      Make more space for arguments.
 417  */
 418 static int
 419 argv_alloc(sp, len)
 420         SCR *sp;
 421         size_t len;
 422 {
 423         ARGS *ap;
 424         EX_PRIVATE *exp;
 425         int cnt, off;
 426
 427         /*
 428          * Allocate room for another argument, always leaving
 429          * enough room for an ARGS structure with a length of 0.
 430          */
 431 #define INCREMENT       20
 432         exp = EXP(sp);
 433         off = exp->argsoff;
 434         if (exp->argscnt == 0 || off + 2 >= exp->argscnt - 1) {
 435                 cnt = exp->argscnt + INCREMENT;
 436                 REALLOC(sp, exp->args, ARGS **, cnt * sizeof(ARGS *));
 437                 if (exp->args == NULL) {
 438                         (void)argv_free(sp);
 439                         goto mem;
 440                 }
 441                 memset(&exp->args[exp->argscnt], 0, INCREMENT * sizeof(ARGS *));
 442                 exp->argscnt = cnt;
 443         }
 444
 445         /* First argument. */
 446         if (exp->args[off] == NULL) {
 447                 CALLOC(sp, exp->args[off], ARGS *, 1, sizeof(ARGS));
 448                 if (exp->args[off] == NULL)
 449                         goto mem;
 450         }
 451
 452         /* First argument buffer. */
 453         ap = exp->args[off];
 454         ap->len = 0;
 455         if (ap->blen < len + 1) {
 456                 ap->blen = len + 1;
 457                 REALLOC(sp, ap->bp, CHAR_T *, ap->blen * sizeof(CHAR_T));
 458                 if (ap->bp == NULL) {
 459                         ap->bp = NULL;
 460                         ap->blen = 0;
 461                         F_CLR(ap, A_ALLOCATED);
 462 mem:                    msgq(sp, M_SYSERR, NULL);
 463                         return (1);
 464                 }
 465                 F_SET(ap, A_ALLOCATED);
 466         }
 467
 468         /* Second argument. */
 469         if (exp->args[++off] == NULL) {
 470                 CALLOC(sp, exp->args[off], ARGS *, 1, sizeof(ARGS));
 471                 if (exp->args[off] == NULL)
 472                         goto mem;
 473         }
 474         /* 0 length serves as end-of-argument marker. */
 475         exp->args[off]->len = 0;
 476         return (0);
 477 }
 478
 479 /*
 480  * argv_free --
 481  *      Free up argument structures.
 482  *
 483  * PUBLIC: int argv_free __P((SCR *));
 484  */
 485 int
 486 argv_free(sp)
 487         SCR *sp;
 488 {
 489         EX_PRIVATE *exp;
 490         int off;
 491
 492         exp = EXP(sp);
 493         if (exp->args != NULL) {
 494                 for (off = 0; off < exp->argscnt; ++off) {
 495                         if (exp->args[off] == NULL)
 496                                 continue;
 497                         if (F_ISSET(exp->args[off], A_ALLOCATED))
 498                                 free(exp->args[off]->bp);
 499                         free(exp->args[off]);
 500                 }
 501                 free(exp->args);
 502         }
 503         exp->args = NULL;
 504         exp->argscnt = 0;
 505         exp->argsoff = 0;
 506         return (0);
 507 }
 508
 509 /*
 510  * argv_lexp --
 511  *      Find all file names matching the prefix and append them to the
 512  *      buffer.
 513  */
 514 static int
 515 argv_lexp(sp, excp, path)
 516         SCR *sp;
 517         EXCMD *excp;
 518         char *path;
 519 {
 520         struct dirent *dp;
 521         DIR *dirp;
 522         EX_PRIVATE *exp;
 523         int off;
 524         size_t dlen, len, nlen;
 525         char *dname, *name, *p;
 526
 527         exp = EXP(sp);
 528
 529         /* Set up the name and length for comparison. */
 530         if ((p = strrchr(path, '/')) == NULL) {
 531                 dname = ".";
 532                 dlen = 0;
 533                 name = path;
 534         } else {
 535                 if (p == path) {
 536                         dname = "/";
 537                         dlen = 1;
 538                 } else {
 539                         *p = '\0';
 540                         dname = path;
 541                         dlen = strlen(path);
 542                 }
 543                 name = p + 1;
 544         }
 545         nlen = strlen(name);
 546
 547         /*
 548          * XXX
 549          * We don't use the d_namlen field, it's not portable enough; we
 550          * assume that d_name is nul terminated, instead.
 551          */
 552         if ((dirp = opendir(dname)) == NULL) {
 553                 msgq_str(sp, M_SYSERR, dname, "%s");
 554                 return (1);
 555         }
 556         for (off = exp->argsoff; (dp = readdir(dirp)) != NULL;) {
 557                 if (nlen == 0) {
 558                         if (dp->d_name[0] == '.')
 559                                 continue;
 560                         len = strlen(dp->d_name);
 561                 } else {
 562                         len = strlen(dp->d_name);
 563                         if (len < nlen || memcmp(dp->d_name, name, nlen))
 564                                 continue;
 565                 }
 566
 567                 /* Directory + name + slash + null. */
 568                 argv_alloc(sp, dlen + len + 2);
 569                 p = exp->args[exp->argsoff]->bp;
 570                 if (dlen != 0) {
 571                         memcpy(p, dname, dlen);
 572                         p += dlen;
 573                         if (dlen > 1 || dname[0] != '/')
 574                                 *p++ = '/';
 575                 }
 576                 memcpy(p, dp->d_name, len + 1);
 577                 exp->args[exp->argsoff]->len = dlen + len + 1;
 578                 ++exp->argsoff;
 579                 excp->argv = exp->args;
 580                 excp->argc = exp->argsoff;
 581         }
 582         closedir(dirp);
 583
 584         if (off == exp->argsoff) {
 585                 /*
 586                  * If we didn't find a match, complain that the expansion
 587                  * failed.  We can't know for certain that's the error, but
 588                  * it's a good guess, and it matches historic practice.
 589                  */
 590                 msgq(sp, M_ERR, "304|Shell expansion failed");
 591                 return (1);
 592         }
 593         qsort(exp->args + off, exp->argsoff - off, sizeof(ARGS *), argv_comp);
 594         return (0);
 595 }
 596
 597 /*
 598  * argv_comp --
 599  *      Alphabetic comparison.
 600  */
 601 static int
 602 argv_comp(a, b)
 603         const void *a, *b;
 604 {
 605         return (strcmp((char *)(*(ARGS **)a)->bp, (char *)(*(ARGS **)b)->bp));
 606 }
 607
 608 /*
 609  * argv_sexp --
 610  *      Fork a shell, pipe a command through it, and read the output into
 611  *      a buffer.
 612  */
 613 static int
 614 argv_sexp(sp, bpp, blenp, lenp)
 615         SCR *sp;
 616         char **bpp;
 617         size_t *blenp, *lenp;
 618 {
 619         enum { SEXP_ERR, SEXP_EXPANSION_ERR, SEXP_OK } rval;
 620         FILE *ifp;
 621         pid_t pid;
 622         size_t blen, len;
 623         int ch, std_output[2];
 624         char *bp, *p, *sh, *sh_path;
 625
 626         /* Secure means no shell access. */
 627         if (O_ISSET(sp, O_SECURE)) {
 628                 msgq(sp, M_ERR,
 629 "289|Shell expansions not supported when the secure edit option is set");
 630                 return (1);
 631         }
 632
 633         sh_path = O_STR(sp, O_SHELL);
 634         if ((sh = strrchr(sh_path, '/')) == NULL)
 635                 sh = sh_path;
 636         else
 637                 ++sh;
 638
 639         /* Local copies of the buffer variables. */
 640         bp = *bpp;
 641         blen = *blenp;
 642
 643         /*
 644          * There are two different processes running through this code, named
 645          * the utility (the shell) and the parent. The utility reads standard
 646          * input and writes standard output and standard error output.  The
 647          * parent writes to the utility, reads its standard output and ignores
 648          * its standard error output.  Historically, the standard error output
 649          * was discarded by vi, as it produces a lot of noise when file patterns
 650          * don't match.
 651          *
 652          * The parent reads std_output[0], and the utility writes std_output[1].
 653          */
 654         ifp = NULL;
 655         std_output[0] = std_output[1] = -1;
 656         if (pipe(std_output) < 0) {
 657                 msgq(sp, M_SYSERR, "pipe");
 658                 return (1);
 659         }
 660         if ((ifp = fdopen(std_output[0], "r")) == NULL) {
 661                 msgq(sp, M_SYSERR, "fdopen");
 662                 goto err;
 663         }
 664
 665         /*
 666          * Do the minimal amount of work possible, the shell is going to run
 667          * briefly and then exit.  We sincerely hope.
 668          */
 669         switch (pid = vfork()) {
 670         case -1:                        /* Error. */
 671                 msgq(sp, M_SYSERR, "vfork");
 672 err:            if (ifp != NULL)
 673                         (void)fclose(ifp);
 674                 else if (std_output[0] != -1)
 675                         close(std_output[0]);
 676                 if (std_output[1] != -1)
 677                         close(std_output[0]);
 678                 return (1);
 679         case 0:                         /* Utility. */
 680                 /* Redirect stdout to the write end of the pipe. */
 681                 (void)dup2(std_output[1], STDOUT_FILENO);
 682
 683                 /* Close the utility's file descriptors. */
 684                 (void)close(std_output[0]);
 685                 (void)close(std_output[1]);
 686                 (void)close(STDERR_FILENO);
 687
 688                 /*
 689                  * XXX
 690                  * Assume that all shells have -c.
 691                  */
 692                 execl(sh_path, sh, "-c", bp, NULL);
 693                 msgq_str(sp, M_SYSERR, sh_path, "118|Error: execl: %s");
 694                 _exit(127);
 695         default:                        /* Parent. */
 696                 /* Close the pipe ends the parent won't use. */
 697                 (void)close(std_output[1]);
 698                 break;
 699         }
 700
 701         /*
 702          * Copy process standard output into a buffer.
 703          *
 704          * !!!
 705          * Historic vi apparently discarded leading \n and \r's from
 706          * the shell output stream.  We don't on the grounds that any
 707          * shell that does that is broken.
 708          */
 709         for (p = bp, len = 0, ch = EOF;
 710             (ch = getc(ifp)) != EOF; *p++ = ch, --blen, ++len)
 711                 if (blen < 5) {
 712                         ADD_SPACE_GOTO(sp, bp, *blenp, *blenp * 2);
 713                         p = bp + len;
 714                         blen = *blenp - len;
 715                 }
 716
 717         /* Delete the final newline, nul terminate the string. */
 718         if (p > bp && (p[-1] == '\n' || p[-1] == '\r')) {
 719                 --p;
 720                 --len;
 721         }
 722         *p = '\0';
 723         *lenp = len;
 724         *bpp = bp;              /* *blenp is already updated. */
 725
 726         if (ferror(ifp))
 727                 goto ioerr;
 728         if (fclose(ifp)) {
 729 ioerr:          msgq_str(sp, M_ERR, sh, "119|I/O error: %s");
 730 alloc_err:      rval = SEXP_ERR;
 731         } else
 732                 rval = SEXP_OK;
 733
 734         /*
 735          * Wait for the process.  If the shell process fails (e.g., "echo $q"
 736          * where q wasn't a defined variable) or if the returned string has
 737          * no characters or only blank characters, (e.g., "echo $5"), complain
 738          * that the shell expansion failed.  We can't know for certain that's
 739          * the error, but it's a good guess, and it matches historic practice.
 740          * This won't catch "echo foo_$5", but that's not a common error and
 741          * historic vi didn't catch it either.
 742          */
 743         if (proc_wait(sp, (long)pid, sh, 1, 0))
 744                 rval = SEXP_EXPANSION_ERR;
 745
 746         for (p = bp; len; ++p, --len)
 747                 if (!isblank(*p))
 748                         break;
 749         if (len == 0)
 750                 rval = SEXP_EXPANSION_ERR;
 751
 752         if (rval == SEXP_EXPANSION_ERR)
 753                 msgq(sp, M_ERR, "304|Shell expansion failed");
 754
 755         return (rval == SEXP_OK ? 0 : 1);
 756 }