aboutsummaryrefslogtreecommitdiff
path: root/toys/pending/sh.c
blob: 0d8eb14bf4717398a8959081ba9c82c51d2524d1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
/* sh.c - toybox shell
 *
 * Copyright 2006 Rob Landley <rob@landley.net>
 *
 * The POSIX-2008/SUSv4 spec for this is at:
 * http://opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
 * and http://opengroup.org/onlinepubs/9699919799/utilities/sh.html
 *
 * The first link describes the following shell builtins:
 *
 *   break colon continue dot eval exec exit export readonly return set shift
 *   times trap unset
 *
 * The second link (the utilities directory) also contains specs for the
 * following shell builtins:
 *
 *   alias bg cd command fc fg getopts hash jobs kill read type ulimit
 *   umask unalias wait
 *
 * Things like the bash man page are good to read too.
 *
 * TODO: "make sh" doesn't work (nofork builtins need to be included)
 * TODO: test that $PS1 color changes work without stupid \[ \] hack
 * TODO: make fake pty wrapper for test infrastructure
 * TODO: // Handle embedded NUL bytes in the command line.
 * TODO: var=val command
 * existing but considered builtins: false kill pwd true
 * buitins: alias bg command fc fg getopts jobs newgrp read umask unalias wait
 * "special" builtins: break continue : . eval exec export readonly return set
 *   shift times trap unset
 * | & ; < > ( ) $ ` \ " ' <space> <tab> <newline>
 * * ? [ # ~ = %
 * ! { } case do done elif else esac fi for if in then until while
 * [[ ]] function select
 * $@ $* $# $? $- $$ $! $0
 * ENV HOME IFS LANG LC_ALL LINENO PATH PPID PS1 PS2 PS4 PWD
 * label:
 * TODO: test exit from "trap EXIT" doesn't recurse
 * TODO: ! history expansion
 *
 * bash man page:
 * control operators || & && ; ;; ;& ;;& ( ) | |& <newline>
 * reserved words
 *   ! case  coproc  do done elif else esac fi for  function  if  in  select
 *   then until while { } time [[ ]]



USE_SH(NEWTOY(cd, NULL, TOYFLAG_NOFORK))
USE_SH(NEWTOY(exit, NULL, TOYFLAG_NOFORK))

USE_SH(NEWTOY(sh, "c:i", TOYFLAG_BIN))
USE_SH(OLDTOY(toysh, sh, TOYFLAG_BIN))
// Login lies in argv[0], so add some aliases to catch that
USE_SH(OLDTOY(-sh, sh, 0))
USE_SH(OLDTOY(-toysh, sh, 0))

config SH
  bool "sh (toysh)"
  default n
  help
    usage: sh [-c command] [script]

    Command shell.  Runs a shell script, or reads input interactively
    and responds to it.

    -c	command line to execute
    -i	interactive mode (default when STDIN is a tty)

# These are here for the help text, they're not selectable and control nothing
config CD
  bool
  default n
  depends on SH
  help
    usage: cd [-PL] [path]

    Change current directory.  With no arguments, go $HOME.

    -P	Physical path: resolve symlinks in path
    -L	Local path: .. trims directories off $PWD (default)

config EXIT
  bool
  default n
  depends on SH
  help
    usage: exit [status]

    Exit shell.  If no return value supplied on command line, use value
    of most recent command, or 0 if none.
*/

#define FOR_sh
#include "toys.h"

GLOBALS(
  char *command;

  long lineno;

  struct double_list functions;
  unsigned options;

  // Running jobs.
  struct sh_job {
    struct sh_job *next, *prev;
    unsigned jobno;

    // Every pipeline has at least one set of arguments or it's Not A Thing
    struct sh_arg {
      char **v;
      int c;
    } pipeline;

    // null terminated array of running processes in pipeline
    struct sh_process {
      struct string_list *delete; // expanded strings
      int pid, exit;   // status? Stopped? Exited?
      struct sh_arg arg;
    } *procs, *proc;
  } *jobs, *job;
  unsigned jobcnt;
)

#define SH_NOCLOBBER 1   // set -C

void cd_main(void)
{
  char *dest = *toys.optargs ? *toys.optargs : getenv("HOME");

  xchdir(dest ? dest : "/");
}

void exit_main(void)
{
  exit(*toys.optargs ? atoi(*toys.optargs) : 0);
}

// like error_msg() but exit from shell scripts
void syntax_err(char *msg, ...)
{
  va_list va;

  va_start(va, msg);
  verror_msg(msg, 0, va);
  va_end(va);

  if (*toys.optargs) xexit();
}

// Print prompt, parsing escapes
static void do_prompt(char *prompt)
{
  char *s, c, cc;

  if (!prompt) prompt = "\\$ ";
  while (*prompt) {
    c = *(prompt++);

    if (c=='!') {
      if (*prompt=='!') prompt++;
      else {
        printf("%ld", TT.lineno);
        continue;
      }
    } else if (c=='\\') {
      int i = 0;

      cc = *(prompt++);
      if (!cc) goto down;

      // \nnn \dD{}hHjlstT@AuvVwW!#$
      // Ignore bash's "nonprintable" hack; query our cursor position instead.
      if (cc=='[' || cc==']') continue;
      else if (cc=='$') putchar(getuid() ? '$' : '#');
      else if (cc=='h' || cc=='H') {
        *toybuf = 0;
        gethostname(toybuf, sizeof(toybuf)-1);
        if (cc=='h' && (s = strchr(toybuf, '.'))) *s = 0;
        fputs(toybuf, stdout);
      } else if (cc=='s') fputs(getbasename(*toys.argv), stdout);
      else {
        if (!(c = unescape(cc))) {
          c = '\\';
          prompt--;
        }
        i++;
      }
      if (!i) continue;
    }
down:
    putchar(c);
  }
  fflush(stdout);
}

// quote removal, brace, tilde, parameter/variable, $(command),
// $((arithmetic)), split, path 
#define NO_PATH  (1<<0)
#define NO_SPLIT (1<<1)
// todo: ${name:?error} causes an error/abort here (syntax_err longjmp?)
static void expand_arg(struct sh_arg *arg, char *new, unsigned flags)
{
  if (!(arg->c&32)) arg->v = xrealloc(arg->v, sizeof(void *)*(arg->c+33));

  arg->v[arg->c++] = new;
  arg->v[arg->c] = 0;

/*
  char *s = word, *new = 0;

  // replacement
  while (*s) {
    if (*s == '$') {
      s++;
    } else if (*strchr("*?[{", *s)) {
      s++;
    } else if (*s == '<' || *s == '>') {
      s++;
    } else s++;
  }

  return new;
*/
}

// Assign one variable
// s: key=val
// type: 0 = whatever it was before, local otherwise
#define TAKE_MEM 0x80000000
void setvar(char *s, unsigned type)
{
  if (type&TAKE_MEM) type ^= TAKE_MEM;
  else s = xstrdup(s);

  // local, export, readonly, integer...
  xsetenv(s, 0);
}

char *getvar(char *s)
{
  return getenv(s);
}

// return length of match found at this point
static int anyof(char *s, char **try)
{
  while (*try) {
    if (strstart(&s, *try)) return strlen(*try);
    try++;
  }

  return 0;
}


// return length of valid prefix that could go before redirect
int redir_prefix(char *word)
{
  char *s = word;

  if (*s == '{') {
    for (s++; isalnum(*s) || *s=='_'; s++);
    if (*s == '}' && s != word+1) s++;
    else s = word;
  } else while (isdigit(*s)) s++;

  return s-word;
}

// todo |&

// rd[0] = next, 1 = prev, 2 = len, 3-x = to/from redirection pairs.
// Execute the commands in a pipeline segment
struct sh_process *run_command(struct sh_arg *arg, int **rdlist)
{
  struct sh_process *pp = xzalloc(sizeof(struct sh_process));
  struct toy_list *tl;
  char *s, *ss, *sss;
  unsigned envlen, j;
  int fd, here = 0, rdcount = 0, *rd = 0, *rr, hfd = 0;

  // Grab variable assignments
  for (envlen = 0; envlen<arg->c; envlen++) {
    s = arg->v[envlen];
    for (j=0; s[j] && s[j] != '=' && s[j] != '\\'; j++);
    if (s[j] != '=') break;
  }

  // perform assignments locally if there's no command
  if (envlen == arg->c) {
    for (j = 0; j<envlen; j++) {
      struct sh_arg aa;

      aa.c = 0;
      expand_arg(&aa, arg->v[j], NO_PATH|NO_SPLIT);
      setvar(*aa.v, TAKE_MEM);
      free(aa.v);
    }
    free(pp);

    return 0;
  }

  // We vfork() instead of fork to support nommu systems, and do
  // redirection setup in the parent process. Open new filehandles
  // and move them to temporary values >10. The rd[] array has pairs of
  // filehandles: child replaces fd1 with fd2 via dup2() and close() after
  // the vfork(). fd2 is <<1, if bottom bit set don't close it (dup instead).
  // If fd2 < 0 it's a here document (parent process writes to a pipe later).

  // Expand arguments and perform redirections
  for (j = envlen; j<arg->c; j++) {

    // Is this a redirect?
    ss = (s = arg->v[j]) + redir_prefix(arg->v[j]);
    fd = anyof(ss, (char *[]){"<<<", "<<-", "<<", "<&", "<>", "<", ">>", ">&",
      ">|", ">", "&>>", "&>", 0});
    if (!fd) {

      // Nope: save/expand argument and loop
      expand_arg(&pp->arg, s, 0);

      continue;
    }

    // Yes. Expand rd[] and find first unused filehandle >10
    if (!(rdcount&31)) {
      if (rd) dlist_lpop((void *)rdlist);
      rd = xrealloc(rd, (2*rdcount+3+2*32)*sizeof(int *));
      dlist_add_nomalloc((void *)rdlist, (void *)rd);
    }
    rr = rd+3+rdcount;
    if (!hfd)
      for (hfd = 10; hfd<99999; hfd++) if (-1 == fcntl(hfd, F_GETFL)) break;

    // error check: premature EOF, target fd too high, or redirect file splits
    if (++j == arg->c || (isdigit(*s) && ss-s>5)) goto flush;
    fd = pp->arg.c;

    // expand arguments for everything but << and <<-
    if (strncmp(ss, "<<", 2) || ss[2] == '<') {
      expand_arg(&pp->arg, arg->v[j], NO_PATH|(NO_SPLIT*!strcmp(ss, "<<<")));
      if (fd+1 != pp->arg.c) goto flush;
      sss = pp->arg.v[--pp->arg.c];
    } else dlist_add((void *)&pp->delete, sss = xstrdup(arg->v[j]));

    // rd[] entries come in pairs: first is which fd gets redirected after
    // vfork(), I.E. the [n] part of [n]<word

    if (isdigit(*ss)) fd = atoi(ss);
    else if (*ss == '{') {
      ss++;
      // when we close a filehandle, we _read_ from {var}, not write to it
      if ((!strcmp(s, "<&") || !strcmp(s, ">&")) && !strcmp(sss, "-")) {
        ss = xstrndup(ss, (s-ss)-1);
        sss = getvar(ss);
        free(ss);
        fd = -1;
        if (sss) fd = atoi(sss);
        if (fd<0) goto flush;
        if (fd>2) {
          rr[0] = fd;
          rr[1] = fd<<1; // close it
          rdcount++;
        }
        continue;
      } else setvar(xmprintf("%.*s=%d", (int)(s-ss), ss, hfd),  TAKE_MEM); 
    } else fd = *ss != '<';
    *rr = fd;

    // at this point for [n]<word s = start of [n], ss = start of <, sss = word

    // second entry in this rd[] pair is new fd to dup2() after vfork(),
    // I.E. for [n]<word the fd if you open("word"). It's stored <<1 and the
    // low bit set means don't close(rr[1]) after dup2(rr[1]>>1, rr[0]);

    // fd<0 means HERE document. Canned input stored earlier, becomes pipe later
    if (!strcmp(s, "<<<") || !strcmp(s, "<<-") || !strcmp(s, "<<")) {
      fd = --here<<2;
      if (s[2] == '-') fd += 1;          // zap tabs
      if (s[strcspn(s, "\"'")]) fd += 2; // it was quoted so no expansion
      rr[1] = fd;
      rdcount++;

      continue;
    }

    // Handle file descriptor duplication/close (&> &>> <& >& with number or -)
    if (strchr(ss, '&') && ss[2] != '>') {
      char *dig = sss;

      // These redirect existing fd so nothing to open()
      while (isdigit(dig)) dig++;
      if (dig-sss>5) {
        s = sss;
        goto flush;
      }

// TODO can't check if fd is open here, must do it when actual redirects happen
      if (!*dig || (*dig=='-' && !dig[1])) {
        rr[1] = (((dig==sss) ? *rr : atoi(sss))<<1)+(*dig != '-');
        rdcount++;

        continue;
      }
    }

    // Permissions to open external file with: < > >> <& >& <> >| &>> &>
    if (!strcmp(ss, "<>")) fd = O_CREAT|O_RDWR;
    else if (strstr(ss, ">>")) fd = O_CREAT|O_APPEND;
    else {
      fd = (*ss != '<') ? O_CREAT|O_WRONLY|O_TRUNC : O_RDONLY;
      if (!strcmp(ss, ">") && (TT.options&SH_NOCLOBBER)) {
        struct stat st;

        // Not _just_ O_EXCL: > /dev/null allowed
        if (stat(sss, &st) || !S_ISREG(st.st_mode)) fd |= O_EXCL;
      }
    }

    // Open the file
// TODO: /dev/fd/# /dev/{stdin,stdout,stderr} /dev/{tcp,udp}/host/port
    if (-1 == (fd = xcreate(sss, fd|WARN_ONLY, 777)) || hfd != dup2(fd, hfd)) {
      pp->exit = 1;
      s = 0;

      goto flush;
    }
    if (fd != hfd) close(fd);
    rr[1] = hfd<<1;
    rdcount++;

    // queue up a 2>&1 ?
    if (strchr(ss, '&')) {
      if (!(31&++rdcount)) rd = xrealloc(rd, (2*rdcount+66)*sizeof(int *));
      rr = rd+3+rdcount;
      rr[0] = 2;
      rr[1] = 1+(1<<1);
      rdcount++;
    }
  }
  if (rd) rd[2] = rdcount;

// todo: ok, now _use_ in_rd[in_rdcount] and rd[rdcount]. :)


// todo use envlen
// todo: check for functions

  // Is this command a builtin that should run in this process?
  if ((tl = toy_find(*pp->arg.v))
    && (tl->flags & (TOYFLAG_NOFORK|TOYFLAG_MAYFORK)))
  {
    struct toy_context temp;
    sigjmp_buf rebound;

    // This fakes lots of what toybox_main() does.
    memcpy(&temp, &toys, sizeof(struct toy_context));
    memset(&toys, 0, sizeof(struct toy_context));

// todo: redirect stdin/out
    if (!sigsetjmp(rebound, 1)) {
      toys.rebound = &rebound;
// must be null terminated
      toy_init(tl, pp->arg.v);
      tl->toy_main();
    }
    pp->exit = toys.exitval;
    if (toys.optargs != toys.argv+1) free(toys.optargs);
    if (toys.old_umask) umask(toys.old_umask);
    memcpy(&toys, &temp, sizeof(struct toy_context));
  } else {
    int pipe[2];

    pipe[0] = 0;
    pipe[1] = 1;
// todo: redirect and pipe
// todo: redirecting stderr needs xpopen3() or rethink
    if (-1 == (pp->pid = xpopen_both(pp->arg.v, pipe)))
      perror_msg("%s: vfork", *pp->arg.v);
// todo: don't close stdin/stdout!
    else pp->exit = xpclose_both(pp->pid, 0);
  }

  s = 0;
flush:
  if (s) {
    syntax_err("bad %s", s);
    if (!pp->exit) pp->exit = 1;
  }
  for (j = 0; j<rdcount; j++) if (rd[4+2*j]>6) close(rd[4+2*j]>>1);
  if (rdcount) free(dlist_lpop((void *)rdlist));

  return pp;
}

// parse next word from command line. Returns end, or 0 if need continuation
// caller eats leading spaces
static char *parse_word(char *start)
{
  int i, j, quote = 0;
  char *end = start, *s;

  // find end of this word
  while (*end) {
    i = 0;

    // Handle quote contexts
    if (quote) {
      // end quote, skip quoted chars
      if (*end == toybuf[quote-1]) quote--, end++;
      else if (toybuf[quote-1] == '"' && *end == '`') toybuf[quote++] = *end++;
      else if (toybuf[quote-1] == '\'' || isspace(*end)) end++;
      else i++;
    } else {
      if (isspace(*end)) break;
      // start quote
      if (strchr("\"'`", *end)) toybuf[quote++] = *end++;
      else if (strstart(&end, "<(") || strstart(&end,">(")) toybuf[quote++]=')';
      else {
        // control chars.
        // 123<<file- parses as 2 args: "123<<" "file-".
        // note: >&; becomes ">&" ";" because first loop, then second loop.
        s = end + redir_prefix(end);
        j = anyof(s, (char *[]){"<<<", "<<-", "<<", "<&", "<>", "<", ">>",
          ">&", ">|", ">", 0});
        if (j) s += j;
        else s = end + anyof(s, (char *[]){";;&", ";;", ";&", ";", "||", "|&",
            "|", "&&", "&>>", "&>", "&", "(", ")", 0});
        if (s != end) return (end == start) ? s : end;
        i++;
      }
    }

    // loop if we already handled a symbol
    if (!i) continue;

    // Things the same unquoted or in double quotes

    // backslash escapes
    if (*end == '\\') {
      if (!end[1] || (end[1]=='\n' && !end[2])) return 0;
      end += 2;
    } else if (*end == '$') {
      // barf if we're near overloading quote stack (nesting ridiculously deep)
      if (quote>4000) {
        syntax_err("tilt");
        return (void *)1;
      }
      end++;
      if (strstart(&end, "((")) {
        // all we care about here are parentheses matching and then ending ))
        for (i = 0;;) {
          if (!*end) return 0;
          if (!i && strstart(&end, "))")) break;
          if (*end == '(') i++;
          else if (*end == ')') i--;
        }
      } else if (-1 != (i = stridx("({[", *end))) {
        toybuf[quote++] = ")}]"[i];
        end++;
      }
    } else end++;
  }

  return quote ? 0 : end;
}

// if then fi for while until select done done case esac break continue return

// Allocate more space for arg, and possibly terminator
void argxtend(struct sh_arg *arg)
{
  if (!(arg->c&31)) arg->v = xrealloc(arg->v, (33+arg->c)*sizeof(void *));
}

// Pipeline segments
struct sh_pipeline {
  struct sh_pipeline *next, *prev;
  int count, here, type;
  struct sh_arg arg[1];
};

// run a series of "command | command && command" with redirects.
int run_pipeline(struct sh_pipeline **pl, int *rd)
{
  struct sh_process *pp;
  int rc = 0;

  for (;;) {
// todo job control
    pp = run_command((*pl)->arg, &rd);
//wait4(pp);
    llist_traverse(pp->delete, free);
    rc = pp->exit;
    free(pp);

    if ((*pl)->next && !(*pl)->next->type) *pl = (*pl)->next;
    else return rc;
  }
}



// scratch space (state held between calls). Don't want to make it global yet
// because this could be reentrant.
struct sh_parse {
  struct sh_pipeline *pipeline;
  struct double_list *expect;
  char *end;
};

// Free one pipeline segment.
void free_pipeline(void *pipeline)
{
  struct sh_pipeline *pl = pipeline;
  int i, j;

  if (pl) for (j=0; j<=pl->count; j++) {
    for (i = 0; i<=pl->arg->c; i++)  free(pl->arg[j].v[i]);
    free(pl->arg[j].v);
  }
  free(pl);
}

// Return end of block corresponding to start of block
struct sh_pipeline *block_end(struct sh_pipeline *pl)
{
  int i = 0;
  do {
    if (pl->type == 1 || pl->type == 'f') i++;
    else if (pl->type == 3) i--;
    pl = pl->next;
  } while (i);

  return pl;
}

// Consume a line of shell script and do what it says. Returns 0 if finished,
// 1 to request another line of input (> prompt).
static int parse_line(char *line, struct sh_parse *sp)
{
  char *start = line, *delete = 0, *end, *last = 0, *s, *ex, done = 0;
  struct sh_pipeline *pl = sp->pipeline ? sp->pipeline->prev : 0;
  struct sh_arg *arg = 0;
  long i;

  // Resume appending to last statement?
  if (pl) {
    arg = pl->arg;

    // Extend/resume quoted block
    if (arg->c<0) {
      delete = start = xmprintf("%s%s", arg->v[arg->c = (-arg->c)-1], start);
      free(arg->v[arg->c]);
      arg->v[arg->c] = 0;

    // is a HERE document in progress?
    } else if (pl->count != pl->here) {
      arg += 1+pl->here;

      argxtend(arg);
      if (strcmp(line, arg->v[arg->c])) {
        // Add this line
        arg->v[arg->c+1] = arg->v[arg->c];
        arg->v[arg->c++] = xstrdup(line);
      // EOF hit, end HERE document
      } else {
        arg->v[arg->c] = 0;
        pl->here++;
      }
      start = 0;
    }
  }

  // Parse words, assemble argv[] pipelines, check flow control and HERE docs
  if (start) for (;;) {

    // Grab HERE document(s) from completed pipeline segment
    if (pl && pl->count == -1) {
      pl->count = 0;
      arg = pl->arg;

      // find arguments of the form [{n}]<<[-] with another one after it
      for (i = 0; i<arg->c; i++) {
        s = arg->v[i] + redir_prefix(arg->v[i]);
        if (strcmp(s, "<<") && strcmp(s, "<<-") && strcmp(s, "<<<")) continue;
        if (i+1 == arg->c) goto flush;

        // queue up HERE EOF so input loop asks for more lines.
        dlist_lpop(&sp->pipeline);
        pl = xrealloc(pl, sizeof(*pl) + ++pl->count*sizeof(struct sh_arg));
        dlist_add_nomalloc((void *)&sp->pipeline, (void *)pl);

        arg[pl->count].v = xzalloc(2*sizeof(void *));
        *arg[pl->count].v = arg->v[++i];
        arg[pl->count].c = -(s[2] == '<'); // note <<< as c = -1
      }
      pl = 0;
    }
    if (done) break;
    s = 0;

    // skip leading whitespace/comment here to know where next word starts
    for (;;) {
      if (isspace(*start)) ++start;
      else if (*start=='#') while (*start && *start != '\n') ++start;
      else break;
    }

    // Parse next word and detect overflow (too many nested quotes).
    if ((end = parse_word(start)) == (void *)1) goto flush;

    // Extend pipeline and argv[] to store result
    if (!pl) {
      pl = xzalloc(sizeof(struct sh_pipeline));
      arg = pl->arg;
      dlist_add_nomalloc((void *)&sp->pipeline, (void *)pl);
    }
    argxtend(arg);

    // Do we need to request another line to finish word (find ending quote)?
    if (!end) {
      // Save unparsed bit of this line, we'll need to re-parse it.
      arg->v[arg->c] = xstrndup(start, strlen(start));
      arg->c = -(arg->c+1);
      free(delete);

      return 1;
    }

    // Ok, we have a word. What does it _mean_?

    // Did we hit end of line or ) outside a function declaration?
    // ) is only saved at start of a statement, ends current statement
    if (end == start || (arg->c && *start == ')' && pl->type!='f')) {
      arg->v[arg->c] = 0;

      if (pl->type == 'f' && arg->c<3) {
        s = "function()";
        goto flush;
      }

      // don't save blank pipeline segments
      if (!arg->c) free_pipeline(dlist_lpop(&sp->pipeline));

      // stop at EOL, else continue with new pipeline segment for )
      if (end == start) done++;
      pl->count = -1;
      last = 0;

      continue;
    }

    // Save argument (strdup) and check for flow control
    s = arg->v[arg->c] = xstrndup(start, end-start);
    start = end;
    if (strchr(";|&", *s)) {

      // flow control without a statement is an error
      if (!arg->c) goto flush;

      // treat ; as newline so we don't have to check both elsewhere.
      if (!strcmp(s, ";")) {
        arg->v[arg->c] = 0;
        free(s);
        s = 0;
      }
      last = s;
      pl->count = -1;

      continue;
    } else arg->v[++arg->c] = 0;

    // is a function() in progress?
    if (arg->c>1 && !strcmp(s, "(")) pl->type = 'f';
    if (pl->type=='f') {
      if (arg->c == 2 && strcmp(s, "(")) goto flush;
      if (arg->c == 3) {
        if (strcmp(s, ")")) goto flush;

        // end function segment, expect function body
        pl->count = -1;
        last = 0;
        dlist_add(&sp->expect, "}");
        dlist_add(&sp->expect, 0);
        dlist_add(&sp->expect, "{");

        continue;
      }

    // flow control is the first word of a pipeline segment
    } else if (arg->c>1) continue;
    ex = sp->expect ? sp->expect->prev->data : 0;

    // When waiting for { it must be next symbol, but can be on a new line.
    if (ex && !strcmp(ex, "{")) {
      if (strcmp(s, "{") || *end) goto flush;
      free(arg->v[--arg->c]);
      free(dlist_lpop(&sp->expect));

      continue;
    }

    end = 0;
    if (!strcmp(s, "if")) end = "then";
    else if (!strcmp(s, "for") || !strcmp(s, "select")
         || !strcmp(s, "while") || !strcmp(s, "until")) end = "do";
    else if (!strcmp(s, "case")) end = "esac";
    else if (!strcmp(s, "{")) end = "}";
    else if (!strcmp(s, "[[")) end = "]]";
    else if (!strcmp(s, "(")) end = ")";

    // Expecting NULL means a statement: any otherwise unrecognized word
    else if (sp->expect && !ex) {
      free(dlist_lpop(&sp->expect));
      continue;
    } else if (!ex) goto check;

    if (end) {
      pl->type = 1;

      // Only innermost statement needed in { { { echo ;} ;} ;} and such
      if (sp->expect && !sp->expect->prev->data) free(dlist_lpop(&sp->expect));

    // If we got here we expect a specific word to end this block: is this it?
    } else if (!strcmp(s, ex)) {
      // can't "if | then" or "while && do", only ; & or newline works
      if (last && strcmp(last, "&")) {
        s = end;
        goto flush;
      }

      free(dlist_lpop(&sp->expect));
      pl->type = anyof(s, (char *[]){"fi", "done", "esac", "}", "]]", ")"})
        ? 3 : 2;

      // if it's a multipart block, what comes next?
      if (!strcmp(s, "do")) end = "done";
      else if (!strcmp(s, "then")) end = "fi\0A";

    // fi could have elif, which queues a then.
    } else if (!strcmp(ex, "fi")) {
      if (!strcmp(s, "elif")) {
        free(dlist_lpop(&sp->expect));
        end = "then";
      // catch duplicate else while we're here
      } else if (!strcmp(s, "else")) {
        if (ex[3] != 'A') {
          s = "2 else";
          goto flush;
        }
        free(dlist_lpop(&sp->expect));
        end = "fi\0B";
      }
    }

    // Do we need to queue up the next thing to expect?
    if (end) {
      if (!pl->type) pl->type = 2;
      dlist_add(&sp->expect, end);
      dlist_add(&sp->expect, 0);    // they're all preceded by a statement
      pl->count = -1;
    }

check:
    // syntax error check: these can't be the first word in an unexpected place
    if (!pl->type && anyof(s, (char *[]){"then", "do", "esac", "}", "]]", ")",
        "done", "then", "fi", "elif", "else"})) goto flush;
  }


  free(delete);

if (0) if (sp->expect) {
dprintf(2, "expectorate\n");
struct double_list *dl;
for (dl = sp->expect; dl; dl = (dl->next == sp->expect) ? 0 : dl->next)
  dprintf(2, "expecting %s\n", dl->data);
if (sp->pipeline) dprintf(2, "count=%d here=%d\n", sp->pipeline->prev->count, sp->pipeline->prev->here);
}

  // advance past <<< arguments (stored as here documents, but no new input)
  pl = sp->pipeline->prev;
  while (pl->count<pl->here && pl->arg[pl->count].c<0)
    pl->arg[pl->count++].c = 0;

  // return if HERE document pending or more flow control needed to complete
  if (sp->expect) return 1;
  if (sp->pipeline && pl->count != pl->here) return 1;

  // At this point, we've don't need more input and can start executing.

if (0) {
dprintf(2, "pipeline now\n");
struct sh_pipeline *ppl = pl;
int q = 0;
for (pl = sp->pipeline; pl ; pl = (pl->next == sp->pipeline) ? 0 : pl->next) {
  for (i = 0; i<pl->arg->c; i++) printf("arg[%d][%ld]=%s\n", q, i, pl->arg->v[i]);
  printf("type=%d term[%d]=%s\n", pl->type, q++, pl->arg->v[pl->arg->c]);
}
pl = ppl;
}

  // **************************** do the thing *******************************

  // Now we have a complete thought and can start running stuff.

  struct blockstack {
    struct blockstack *next;
    struct sh_pipeline *start, *now, *end;
    int run, val, *redir;
  } *blk = 0, *new;

  // iterate through the commands
  dlist_terminate(pl = sp->pipeline);
  while (pl) {
    s = *pl->arg->v;

    // Normal executable statement?
    if (!pl->type) {

// inherit redirects?
// returns last statement of pipeline
      if (!blk) toys.exitval = run_pipeline(&pl, 0);
      else if (blk->run) toys.exitval = run_pipeline(&pl, blk->redir);
      else do pl = pl->next; while (!pl->type);

    // Starting a new block?
    } else if (pl->type == 1) {
      struct sh_pipeline *end = block_end(pl);

      // If we're not running this, skip ahead.
      if (blk && !blk->run) {
        pl = end;
        continue;
      }

      // If we are, save context and add it to the stack.
      new = xzalloc(sizeof(*blk));
      new->next = blk;
      blk = new;
      blk->start = blk->now = pl;
      blk->end = end;
      blk->run = 1;

// todo perform block end redirects

    } else if (pl->type == 2) {

      // Handle if statement
      if (!strcmp(s, "then")) blk->run = blk->run && !toys.exitval;
      else if (!strcmp(s, "else") || !strcmp(s, "elif")) blk->run = !blk->run;

    // If ending a block, pop stack.
    } else if (pl->type == 3) {
      new = blk->next;
      free(blk);
      blk = new;

// todo unwind redirects

    } else if (pl->type == 'f') {
dprintf(2, "skipped function definition %s\n", *pl->arg->v);
pl = block_end(pl);
    }



/*
if/then/elif/else/fi
for select while until/do/done
case/esac
{/}
[[/]]
(/)
function/}
*/
    pl = pl->next;
  }

  s = 0;
flush:
  if (s) syntax_err("bad %s", s);
  while ((pl = dlist_pop(&sp->pipeline))) free_pipeline(pl);
  llist_traverse(sp->expect, free);

  return 0;
}

void sh_main(void)
{
  FILE *f;
  struct sh_parse scratch;
  int prompt = 0;

  // Set up signal handlers and grab control of this tty.

  memset(&scratch, 0, sizeof(scratch));
  if (TT.command) f = fmemopen(TT.command, strlen(TT.command), "r");
  else if (*toys.optargs) f = xfopen(*toys.optargs, "r");
  else {
    f = stdin;
    if (isatty(0)) toys.optflags |= FLAG_i;
  }

  for (;;) {
    char *new = 0;
    size_t linelen = 0;

    // Prompt and read line
    if (f == stdin) {
      char *s = getenv(prompt ? "PS2" : "PS1");

      if (!s) s = prompt ? "> " : (getpid() ? "\\$ " : "# ");
      do_prompt(s);
    } else TT.lineno++;
    if (1>(linelen = getline(&new, &linelen, f ? f : stdin))) break;
    if (new[linelen-1] == '\n') new[--linelen] = 0;

// TODO if (!isspace(*new)) add_to_history(line);

    // returns 0 if line consumed, command if it needs more data
    prompt = parse_line(new, &scratch);
    free(new);
  }

  if (prompt) error_exit("%ld:unfinished line"+4*!TT.lineno, TT.lineno);
  toys.exitval = f && ferror(f);
}