summaryrefslogtreecommitdiff
path: root/job.c
blob: daefc5cbd2c59672b5159629012bd84a532ce7ee (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
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
/* Job execution and handling for GNU Make.
Copyright (C) 1988, 89, 90, 91, 92, 93, 94, 1995 Free Software Foundation, Inc.
This file is part of GNU Make.

GNU Make is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Make is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Make; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "make.h"
#include "commands.h"
#include "job.h"
#include "file.h"
#include "variable.h"
#include <assert.h>

/* Default shell to use.  */
char default_shell[] = "/bin/sh";

#ifdef __MSDOS__
#include <process.h>
static int dos_pid = 123;
static int dos_status;
static char *dos_bname;
static char *dos_bename;
static int dos_batch_file;
#endif /* MSDOS.  */

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#else
#include <sys/file.h>
#endif


/* If NGROUPS_MAX == 0 then try other methods for finding a real value.  */
#if defined (NGROUPS_MAX) && NGROUPS_MAX == 0
#undef NGROUPS_MAX
#endif /* NGROUPS_MAX == 0 */

#ifndef	NGROUPS_MAX
#ifdef	POSIX
#define	GET_NGROUPS_MAX	sysconf (_SC_NGROUPS_MAX)
#else	/* Not POSIX.  */
#define	NGROUPS_MAX	NGROUPS
#endif	/* POSIX.  */
#endif

#ifdef	HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif

#ifdef	HAVE_WAITPID
#define	WAIT_NOHANG(status)	waitpid (-1, (status), WNOHANG)
#else	/* Don't have waitpid.  */
#ifdef	HAVE_WAIT3
#ifndef	wait3
extern int wait3 ();
#endif
#define	WAIT_NOHANG(status)	wait3 ((status), WNOHANG, (struct rusage *) 0)
#endif	/* Have wait3.  */
#endif	/* Have waitpid.  */

#if	!defined (wait) && !defined (POSIX)
extern int wait ();
#endif

#ifndef	HAVE_UNION_WAIT

#define	WAIT_T int

#ifndef	WTERMSIG
#define WTERMSIG(x) ((x) & 0x7f)
#endif
#ifndef	WCOREDUMP
#define WCOREDUMP(x) ((x) & 0x80)
#endif
#ifndef	WEXITSTATUS
#define WEXITSTATUS(x) (((x) >> 8) & 0xff)
#endif
#ifndef	WIFSIGNALED
#define WIFSIGNALED(x) (WTERMSIG (x) != 0)
#endif
#ifndef	WIFEXITED
#define WIFEXITED(x) (WTERMSIG (x) == 0)
#endif

#else	/* Have `union wait'.  */

#define WAIT_T union wait
#ifndef	WTERMSIG
#define WTERMSIG(x)	((x).w_termsig)
#endif
#ifndef	WCOREDUMP
#define WCOREDUMP(x)	((x).w_coredump)
#endif
#ifndef WEXITSTATUS
#define WEXITSTATUS(x)	((x).w_retcode)
#endif
#ifndef	WIFSIGNALED
#define	WIFSIGNALED(x)	(WTERMSIG(x) != 0)
#endif
#ifndef	WIFEXITED
#define	WIFEXITED(x)	(WTERMSIG(x) == 0)
#endif

#endif	/* Don't have `union wait'.  */


#ifndef	HAVE_UNISTD_H
extern int dup2 ();
extern int execve ();
extern void _exit ();
extern int geteuid (), getegid ();
extern int setgid (), getgid ();
#endif

#ifndef	getdtablesize
#ifdef HAVE_GETDTABLESIZE
extern int getdtablesize ();
#else
#ifdef HAVE_SYSCONF_OPEN_MAX
#define getdtablesize()		((int) sysconf (_SC_OPEN_MAX))
#else
#include <sys/param.h>
#define getdtablesize() NOFILE
#if !defined (NOFILE) && defined (NOFILES_MAX)
/* SCO 3.2 "devsys 4.2" defines NOFILES_{MIN,MAX} in lieu of NOFILE.  */
#define NOFILE	NOFILES_MAX
#endif
#endif
#endif
#endif

extern int getloadavg ();
extern int start_remote_job_p ();
extern int start_remote_job (), remote_status ();

RETSIGTYPE child_handler ();
static void free_child (), start_job_command ();
static int load_too_high (), job_next_command ();

/* Chain of all live (or recently deceased) children.  */

struct child *children = 0;

/* Number of children currently running.  */

unsigned int job_slots_used = 0;

/* Nonzero if the `good' standard input is in use.  */

static int good_stdin_used = 0;

/* Chain of children waiting to run until the load average goes down.  */

static struct child *waiting_jobs = 0;

/* Write an error message describing the exit status given in
   EXIT_CODE, EXIT_SIG, and COREDUMP, for the target TARGET_NAME.
   Append "(ignored)" if IGNORED is nonzero.  */

static void
child_error (target_name, exit_code, exit_sig, coredump, ignored)
     char *target_name;
     int exit_code, exit_sig, coredump;
     int ignored;
{
  if (exit_sig == 0)
    error (ignored ? "[%s] Error %d (ignored)" :
	   "*** [%s] Error %d",
	   target_name, exit_code);
  else
    error ("*** [%s] %s%s",
	   target_name, strsignal (exit_sig),
	   coredump ? " (core dumped)" : "");
}

static unsigned int dead_children = 0;

/* Notice that a child died.
   reap_children should be called when convenient.  */
RETSIGTYPE
child_handler (sig)
     int sig;
{
  ++dead_children;

  if (debug_flag)
    printf ("Got a SIGCHLD; %d unreaped children.\n", dead_children);
}

extern int shell_function_pid, shell_function_completed;

/* Reap dead children, storing the returned status and the new command
   state (`cs_finished') in the `file' member of the `struct child' for the
   dead child, and removing the child from the chain.  If BLOCK nonzero,
   reap at least one child, waiting for it to die if necessary.  If ERR is
   nonzero, print an error message first.  */

void
reap_children (block, err)
     int block, err;
{
  WAIT_T status;

  while ((children != 0 || shell_function_pid != 0) &&
	 (block || dead_children > 0))
    {
      int remote = 0;
      register int pid;
      int exit_code, exit_sig, coredump;
      register struct child *lastc, *c;
      int child_failed;
      int any_remote, any_local;

      if (err && dead_children == 0)
	{
	  /* We might block for a while, so let the user know why.  */
	  fflush (stdout);
	  error ("*** Waiting for unfinished jobs....");
	}

      /* We have one less dead child to reap.
	 The test and decrement are not atomic; if it is compiled into:
	 	register = dead_children - 1;
		dead_children = register;
	 a SIGCHLD could come between the two instructions.
	 child_handler increments dead_children.
	 The second instruction here would lose that increment.  But the
	 only effect of dead_children being wrong is that we might wait
	 longer than necessary to reap a child, and lose some parallelism;
	 and we might print the "Waiting for unfinished jobs" message above
	 when not necessary.  */

      if (dead_children != 0)
	--dead_children;

      any_remote = 0;
      any_local = shell_function_pid != -1;
      for (c = children; c != 0; c = c->next)
	{
	  any_remote |= c->remote;
	  any_local |= ! c->remote;
	  if (debug_flag)
	    printf ("Live child 0x%08lx PID %d%s\n",
		    (unsigned long int) c,
		    c->pid, c->remote ? " (remote)" : "");
	}

      /* First, check for remote children.  */
      if (any_remote)
	pid = remote_status (&exit_code, &exit_sig, &coredump, 0);
      else
	pid = 0;
      if (pid < 0)
	{
	remote_status_lose:
#ifdef	EINTR
	  if (errno == EINTR)
	    continue;
#endif
	  pfatal_with_name ("remote_status");
	}
      else if (pid == 0)
	{
#ifndef	__MSDOS__
	  /* No remote children.  Check for local children.  */

	  if (any_local)
	    {
#ifdef	WAIT_NOHANG
	      if (!block)
		pid = WAIT_NOHANG (&status);
	      else
#endif
		pid = wait (&status);
	    }
	  else
	    pid = 0;

	  if (pid < 0)
	    {
#ifdef	EINTR
	      if (errno == EINTR)
		continue;
#endif
	      pfatal_with_name ("wait");
	    }
	  else if (pid == 0)
	    {
	      /* No local children.  */
	      if (block && any_remote)
		{
		  /* Now try a blocking wait for a remote child.  */
		  pid = remote_status (&exit_code, &exit_sig, &coredump, 1);
		  if (pid < 0)
		    goto remote_status_lose;
		  else if (pid == 0)
		    /* No remote children either.  Finally give up.  */
		    break;
		  else
		    /* We got a remote child.  */
		    remote = 1;
		}
	      else
		break;
	    }
	  else
	    {
	      /* Chop the status word up.  */
	      exit_code = WEXITSTATUS (status);
	      exit_sig = WIFSIGNALED (status) ? WTERMSIG (status) : 0;
	      coredump = WCOREDUMP (status);
	    }
#else	/* MSDOS.  */
	  /* Life is very different on MSDOS.  */
	  pid = dos_pid - 1;
	  status = dos_status;
	  exit_code = dos_status;
	  exit_sig = 0;
	  coredump = 0;
#endif	/* Not MSDOS.  */
	}
      else
	/* We got a remote child.  */
	remote = 1;

      /* Check if this is the child of the `shell' function.  */
      if (!remote && pid == shell_function_pid)
	{
	  /* It is.  Leave an indicator for the `shell' function.  */
	  if (exit_sig == 0 && exit_code == 127)
	    shell_function_completed = -1;
	  else
	    shell_function_completed = 1;
	  break;
	}

      child_failed = exit_sig != 0 || exit_code != 0;

      /* Search for a child matching the deceased one.  */
      lastc = 0;
      for (c = children; c != 0; lastc = c, c = c->next)
	if (c->remote == remote && c->pid == pid)
	  break;

      if (c == 0)
	{
	  /* An unknown child died.  */
	  char buf[100];
	  sprintf (buf, "Unknown%s job %d", remote ? " remote" : "", pid);
	  if (child_failed)
	    child_error (buf, exit_code, exit_sig, coredump,
			 ignore_errors_flag);
	  else
	    error ("%s finished.", buf);
	}
      else
	{
	  if (debug_flag)
	    printf ("Reaping %s child 0x%08lx PID %d%s\n",
		    child_failed ? "losing" : "winning",
		    (unsigned long int) c,
		    c->pid, c->remote ? " (remote)" : "");

	  /* If this child had the good stdin, say it is now free.  */
	  if (c->good_stdin)
	    good_stdin_used = 0;

	  if (child_failed && !c->noerror && !ignore_errors_flag)
	    {
	      /* The commands failed.  Write an error message,
		 delete non-precious targets, and abort.  */
	      static int delete_on_error = -1;
	      child_error (c->file->name, exit_code, exit_sig, coredump, 0);
	      c->file->update_status = 2;
	      if (delete_on_error == -1)
		{
		  struct file *f = lookup_file (".DELETE_ON_ERROR");
		  delete_on_error = f != 0 && f->is_target;
		}
	      if (exit_sig != 0 || delete_on_error)
		delete_child_targets (c);
	    }
	  else
	    {
	      if (child_failed)
		{
		  /* The commands failed, but we don't care.  */
		  child_error (c->file->name,
			       exit_code, exit_sig, coredump, 1);
		  child_failed = 0;
		}

	      /* If there are more commands to run, try to start them.  */
	      if (job_next_command (c))
		{
		  if (handling_fatal_signal)
		    {
		      /* Never start new commands while we are dying.
			 Since there are more commands that wanted to be run,
			 the target was not completely remade.  So we treat
			 this as if a command had failed.  */
		      c->file->update_status = 2;
		    }
		  else
		    {
		      /* Check again whether to start remotely.
			 Whether or not we want to changes over time.
			 Also, start_remote_job may need state set up
			 by start_remote_job_p.  */
		      c->remote = start_remote_job_p ();
		      start_job_command (c);
		      if (c->file->command_state == cs_running)
			/* We successfully started the new command.
			   Loop to reap more children.  */
			continue;
		    }

		  if (c->file->update_status != 0)
		    /* We failed to start the commands.  */
		    delete_child_targets (c);
		}
	      else
		/* There are no more commands.  We got through them all
		   without an unignored error.  Now the target has been
		   successfully updated.  */
		c->file->update_status = 0;
	    }

	  /* When we get here, all the commands for C->file are finished
	     (or aborted) and C->file->update_status contains 0 or 2.  But
	     C->file->command_state is still cs_running if all the commands
	     ran; notice_finish_file looks for cs_running to tell it that
	     it's interesting to check the file's modtime again now.  */

	  if (! handling_fatal_signal)
	    /* Notice if the target of the commands has been changed.
	       This also propagates its values for command_state and
	       update_status to its also_make files.  */
	    notice_finished_file (c->file);

	  if (debug_flag)
	    printf ("Removing child 0x%08lx PID %d%s from chain.\n",
		    (unsigned long int) c,
		    c->pid, c->remote ? " (remote)" : "");

	  /* Remove the child from the chain and free it.  */
	  if (lastc == 0)
	    children = c->next;
	  else
	    lastc->next = c->next;
	  if (! handling_fatal_signal) /* Avoid nonreentrancy.  */
	    free_child (c);

	  /* There is now another slot open.  */
	  --job_slots_used;

	  /* If the job failed, and the -k flag was not given, die,
	     unless we are already in the process of dying.  */
	  if (!err && child_failed && !keep_going_flag)
	    die (2);
	}

      /* Only block for one child.  */
      block = 0;
    }
}

/* Free the storage allocated for CHILD.  */

static void
free_child (child)
     register struct child *child;
{
  if (child->command_lines != 0)
    {
      register unsigned int i;
      for (i = 0; i < child->file->cmds->ncommand_lines; ++i)
	free (child->command_lines[i]);
      free ((char *) child->command_lines);
    }

  if (child->environment != 0)
    {
      register char **ep = child->environment;
      while (*ep != 0)
	free (*ep++);
      free ((char *) child->environment);
    }

  free ((char *) child);
}

#ifdef	POSIX
#ifdef	__MSDOS__
void
unblock_sigs ()
{
  return;
}
#else
extern sigset_t fatal_signal_set;

void
unblock_sigs ()
{
  sigset_t empty;
  sigemptyset (&empty);
  sigprocmask (SIG_SETMASK, &empty, (sigset_t *) 0);
}
#endif
#endif

/* Start a job to run the commands specified in CHILD.
   CHILD is updated to reflect the commands and ID of the child process.  */

static void
start_job_command (child)
     register struct child *child;
{
  static int bad_stdin = -1;
  register char *p;
  int flags;
  char **argv;

  /* Combine the flags parsed for the line itself with
     the flags specified globally for this target.  */
  flags = (child->file->command_flags
	   | child->file->cmds->lines_flags[child->command_line - 1]);

  p = child->command_ptr;
  child->noerror = flags & COMMANDS_NOERROR;
  while (*p != '\0')
    {
      if (*p == '@')
	flags |= COMMANDS_SILENT;
      else if (*p == '+')
	flags |= COMMANDS_RECURSE;
      else if (*p == '-')
	child->noerror = 1;
      else if (!isblank (*p) && *p != '+')
	break;
      ++p;
    }

  /* If -q was given, just say that updating `failed'.  The exit status of
     1 tells the user that -q is saying `something to do'; the exit status
     for a random error is 2.  */
  if (question_flag && !(flags & COMMANDS_RECURSE))
    {  
      child->file->update_status = 1;
      notice_finished_file (child->file);
      return;
    }

  /* There may be some preceding whitespace left if there
     was nothing but a backslash on the first line.  */
  p = next_token (p);
  
  /* Figure out an argument list from this command line.  */
  
  {
    char *end;
    argv = construct_command_argv (p, &end, child->file);
    if (end == NULL)
      child->command_ptr = NULL;
    else
      {
	*end++ = '\0';
	child->command_ptr = end;
      }
  }

  if (touch_flag && !(flags & COMMANDS_RECURSE))
    {
      /* Go on to the next command.  It might be the recursive one.
	 We construct ARGV only to find the end of the command line.  */
      free (argv[0]);
      free ((char *) argv);
      argv = 0;
    }

  if (argv == 0)
    {
    next_command:
      /* This line has no commands.  Go to the next.  */
      if (job_next_command (child))
	start_job_command (child);
      else
	{
	  /* No more commands.  All done.  */
	  child->file->update_status = 0;
	  notice_finished_file (child->file);
	}
      return;
    }

  /* Print out the command.  */

  if (just_print_flag || (!(flags & COMMANDS_SILENT) && !silent_flag))
    puts (p);

  /* Tell update_goal_chain that a command has been started on behalf of
     this target.  It is important that this happens here and not in
     reap_children (where we used to do it), because reap_children might be
     reaping children from a different target.  We want this increment to
     guaranteedly indicate that a command was started for the dependency
     chain (i.e., update_file recursion chain) we are processing.  */

  ++commands_started;

  /* If -n was given, recurse to get the next line in the sequence.  */

  if (just_print_flag && !(flags & COMMANDS_RECURSE))
    {
      free (argv[0]);
      free ((char *) argv);
      goto next_command;
    }

  /* Flush the output streams so they won't have things written twice.  */

  fflush (stdout);
  fflush (stderr);
  
  /* Set up a bad standard input that reads from a broken pipe.  */

  if (bad_stdin == -1)
    {
      /* Make a file descriptor that is the read end of a broken pipe.
	 This will be used for some children's standard inputs.  */
      int pd[2];
      if (pipe (pd) == 0)
	{
	  /* Close the write side.  */
	  (void) close (pd[1]);
	  /* Save the read side.  */
	  bad_stdin = pd[0];

	  /* Set the descriptor to close on exec, so it does not litter any
	     child's descriptor table.  When it is dup2'd onto descriptor 0,
	     that descriptor will not close on exec.  */
#ifdef FD_SETFD
#ifndef FD_CLOEXEC
#define FD_CLOEXEC 1
#endif
	  (void) fcntl (bad_stdin, F_SETFD, FD_CLOEXEC);
#endif
	}
    }

  /* Decide whether to give this child the `good' standard input
     (one that points to the terminal or whatever), or the `bad' one
     that points to the read side of a broken pipe.  */

  child->good_stdin = !good_stdin_used;
  if (child->good_stdin)
    good_stdin_used = 1;

  child->deleted = 0;

  /* Set up the environment for the child.  */
  if (child->environment == 0)
    child->environment = target_environment (child->file);

#ifndef	__MSDOS__

  /* start_waiting_job has set CHILD->remote if we can start a remote job.  */
  if (child->remote)
    {
      int is_remote, id, used_stdin;
      if (start_remote_job (argv, child->environment,
			    child->good_stdin ? 0 : bad_stdin,
			    &is_remote, &id, &used_stdin))
	goto error;
      else
	{
	  if (child->good_stdin && !used_stdin)
	    {
	      child->good_stdin = 0;
	      good_stdin_used = 0;
	    }
	  child->remote = is_remote;
	  child->pid = id;
	}
    }
  else
    {
      /* Fork the child process.  */

      char **parent_environ;

#ifdef	 POSIX
      (void) sigprocmask (SIG_BLOCK, &fatal_signal_set, (sigset_t *) 0);
#else
#ifdef	HAVE_SIGSETMASK
      (void) sigblock (fatal_signal_mask);
#endif
#endif

      child->remote = 0;
      parent_environ = environ;
      child->pid = vfork ();
      environ = parent_environ;	/* Restore value child may have clobbered.  */
      if (child->pid == 0)
	{
	  /* We are the child side.  */
	  unblock_sigs ();
	  child_execute_job (child->good_stdin ? 0 : bad_stdin, 1,
			     argv, child->environment);
	}
      else if (child->pid < 0)
	{
	  /* Fork failed!  */
	  unblock_sigs ();
	  perror_with_name ("vfork", "");
	  goto error;
	}
    }

#else	/* MSDOS.  */
  dos_status = spawnvpe (P_WAIT, argv[0], argv, child->environment);
  ++dead_children;
  child->pid = dos_pid++;
  if (dos_batch_file)
   {
     dos_batch_file = 0;
     remove (dos_bname);	/* Ignore errors.  */
     if (access (dos_bename, 0))
       dos_status = 1;
     else
       dos_status = 0;
     remove (dos_bename);
   }
#endif	/* Not MSDOS.  */

  /* We are the parent side.  Set the state to
     say the commands are running and return.  */

  set_command_state (child->file, cs_running);

  /* Free the storage used by the child's argument list.  */

  free (argv[0]);
  free ((char *) argv);

  return;

 error:
  child->file->update_status = 2;
  notice_finished_file (child->file);
}

/* Try to start a child running.
   Returns nonzero if the child was started (and maybe finished), or zero if
   the load was too high and the child was put on the `waiting_jobs' chain.  */

static int
start_waiting_job (c)
     struct child *c;
{
  /* If we can start a job remotely, we always want to, and don't care about
     the local load average.  We record that the job should be started
     remotely in C->remote for start_job_command to test.  */

  c->remote = start_remote_job_p ();

  /* If this job is to be started locally, and we are already running
     some jobs, make this one wait if the load average is too high.  */
  if (!c->remote && job_slots_used > 0 && load_too_high ())
    {
      /* Put this child on the chain of children waiting
	 for the load average to go down.  */
      set_command_state (c->file, cs_running);
      c->next = waiting_jobs;
      waiting_jobs = c;
      return 0;
    }

  /* Start the first command; reap_children will run later command lines.  */
  start_job_command (c);

  switch (c->file->command_state)
    {
    case cs_running:
      c->next = children;
      if (debug_flag)
	printf ("Putting child 0x%08lx PID %05d%s on the chain.\n",
		(unsigned long int) c,
		c->pid, c->remote ? " (remote)" : "");
      children = c;
      /* One more job slot is in use.  */
      ++job_slots_used;
      unblock_sigs ();
      break;

    case cs_not_started:
      /* All the command lines turned out to be empty.  */
      c->file->update_status = 0;
      /* FALLTHROUGH */

    case cs_finished:
      notice_finished_file (c->file);
      free_child (c);
      break;

    default:
      assert (c->file->command_state == cs_finished);
      break;
    }

  return 1;
}

/* Create a `struct child' for FILE and start its commands running.  */

void
new_job (file)
     register struct file *file;
{
  register struct commands *cmds = file->cmds;
  register struct child *c;
  char **lines;
  register unsigned int i;

  /* Let any previously decided-upon jobs that are waiting
     for the load to go down start before this new one.  */
  start_waiting_jobs ();

  /* Reap any children that might have finished recently.  */
  reap_children (0, 0);

  /* Chop the commands up into lines if they aren't already.  */
  chop_commands (cmds);

  if (job_slots != 0)
    /* Wait for a job slot to be freed up.  */
    while (job_slots_used == job_slots)
      reap_children (1, 0);

  /* Expand the command lines and store the results in LINES.  */
  lines = (char **) xmalloc (cmds->ncommand_lines * sizeof (char *));
  for (i = 0; i < cmds->ncommand_lines; ++i)
    {
      /* Collapse backslash-newline combinations that are inside variable
	 or function references.  These are left alone by the parser so
	 that they will appear in the echoing of commands (where they look
	 nice); and collapsed by construct_command_argv when it tokenizes.
	 But letting them survive inside function invocations loses because
	 we don't want the functions to see them as part of the text.  */

      char *in, *out, *ref;

      /* IN points to where in the line we are scanning.
	 OUT points to where in the line we are writing.
	 When we collapse a backslash-newline combination,
	 IN gets ahead out OUT.  */

      in = out = cmds->command_lines[i];
      while ((ref = index (in, '$')) != 0)
	{
	  ++ref;		/* Move past the $.  */

	  if (out != in)
	    /* Copy the text between the end of the last chunk
	       we processed (where IN points) and the new chunk
	       we are about to process (where REF points).  */
	    bcopy (in, out, ref - in);

	  /* Move both pointers past the boring stuff.  */
	  out += ref - in;
	  in = ref;

	  if (*ref == '(' || *ref == '{')
	    {
	      char openparen = *ref;
	      char closeparen = openparen == '(' ? ')' : '}';
	      int count;
	      char *p;

	      *out++ = *in++;	/* Copy OPENPAREN.  */
	      /* IN now points past the opening paren or brace.
		 Count parens or braces until it is matched.  */
	      count = 0;
	      while (*in != '\0')
		{
		  if (*in == closeparen && --count < 0)
		    break;
		  else if (*in == '\\' && in[1] == '\n')
		    {
		      /* We have found a backslash-newline inside a
			 variable or function reference.  Eat it and
			 any following whitespace.  */

		      int quoted = 0;
		      for (p = in - 1; p > ref && *p == '\\'; --p)
			quoted = !quoted;

		      if (quoted)
			/* There were two or more backslashes, so this is
			   not really a continuation line.  We don't collapse
			   the quoting backslashes here as is done in
			   collapse_continuations, because the line will
			   be collapsed again after expansion.  */
			*out++ = *in++;
		      else
			{
			  /* Skip the backslash, newline and
			     any following whitespace.  */
			  in = next_token (in + 2);

			  /* Discard any preceding whitespace that has
			     already been written to the output.  */
			  while (out > ref && isblank (out[-1]))
			    --out;

			  /* Replace it all with a single space.  */
			  *out++ = ' ';
			}
		    }
		  else
		    {
		      if (*in == openparen)
			++count;

		      *out++ = *in++;
		    }
		}
	    }
	}

      /* There are no more references in this line to worry about.
	 Copy the remaining uninteresting text to the output.  */
      if (out != in)
	strcpy (out, in);

      /* Finally, expand the line.  */
      lines[i] = allocated_variable_expand_for_file (cmds->command_lines[i],
						     file);
    }

  /* Start the command sequence, record it in a new
     `struct child', and add that to the chain.  */

  c = (struct child *) xmalloc (sizeof (struct child));
  c->file = file;
  c->command_lines = lines;
  c->command_line = 0;
  c->command_ptr = 0;
  c->environment = 0;

  /* Fetch the first command line to be run.  */
  job_next_command (c);

  /* The job is now primed.  Start it running.
     (This will notice if there are in fact no commands.)  */
  start_waiting_job (c);

  if (job_slots == 1)
    /* Since there is only one job slot, make things run linearly.
       Wait for the child to die, setting the state to `cs_finished'.  */
    while (file->command_state == cs_running)
      reap_children (1, 0);
}

/* Move CHILD's pointers to the next command for it to execute.
   Returns nonzero if there is another command.  */

static int
job_next_command (child)
     struct child *child;
{
  while (child->command_ptr == 0 || *child->command_ptr == '\0')
    {
      /* There are no more lines in the expansion of this line.  */
      if (child->command_line == child->file->cmds->ncommand_lines)
	{
	  /* There are no more lines to be expanded.  */
	  child->command_ptr = 0;
	  return 0;
	}
      else
	/* Get the next line to run.  */
	child->command_ptr = child->command_lines[child->command_line++];
    }
  return 1;
}

static int
load_too_high ()
{
#ifdef	__MSDOS__
  return 1;
#else
  extern int getloadavg ();
  double load;

  if (max_load_average < 0)
    return 0;

  make_access ();
  if (getloadavg (&load, 1) != 1)
    {
      static int lossage = -1;
      /* Complain only once for the same error.  */
      if (lossage == -1 || errno != lossage)
	{
	  if (errno == 0)
	    /* An errno value of zero means getloadavg is just unsupported.  */
	    error ("cannot enforce load limits on this operating system");
	  else
	    perror_with_name ("cannot enforce load limit: ", "getloadavg");
	}
      lossage = errno;
      load = 0;
    }
  user_access ();

  return load >= max_load_average;
#endif
}

/* Start jobs that are waiting for the load to be lower.  */

void
start_waiting_jobs ()
{
  struct child *job;

  if (waiting_jobs == 0)
    return;

  do
    {
      /* Check for recently deceased descendants.  */
      reap_children (0, 0);

      /* Take a job off the waiting list.  */
      job = waiting_jobs;
      waiting_jobs = job->next;

      /* Try to start that job.  We break out of the loop as soon
	 as start_waiting_job puts one back on the waiting list.  */
    } while (start_waiting_job (job) && waiting_jobs != 0);
}

/* Replace the current process with one executing the command in ARGV.
   STDIN_FD and STDOUT_FD are used as the process's stdin and stdout; ENVP is
   the environment of the new program.  This function does not return.  */

void
child_execute_job (stdin_fd, stdout_fd, argv, envp)
     int stdin_fd, stdout_fd;
     char **argv, **envp;
{
  if (stdin_fd != 0)
    (void) dup2 (stdin_fd, 0);
  if (stdout_fd != 1)
    (void) dup2 (stdout_fd, 1);
  if (stdin_fd != 0)
    (void) close (stdin_fd);
  if (stdout_fd != 1)
    (void) close (stdout_fd);

  /* Run the command.  */
  exec_command (argv, envp);
}

/* Replace the current process with one running the command in ARGV,
   with environment ENVP.  This function does not return.  */

void
exec_command (argv, envp)
     char **argv, **envp;
{
  /* Be the user, permanently.  */
  child_access ();

  /* Run the program.  */
  environ = envp;
  execvp (argv[0], argv);
  
  switch (errno)
    {
    case ENOENT:
      error ("%s: Command not found", argv[0]);
      break;
    case ENOEXEC:
      {
	/* The file is not executable.  Try it as a shell script.  */
	extern char *getenv ();
	char *shell;
	char **new_argv;
	int argc;

	shell = getenv ("SHELL");
	if (shell == 0)
	  shell = default_shell;

	argc = 1;
	while (argv[argc] != 0)
	  ++argc;

	new_argv = (char **) alloca ((1 + argc + 1) * sizeof (char *));
	new_argv[0] = shell;
	new_argv[1] = argv[0];
	while (argc > 0)
	  {
	    new_argv[1 + argc] = argv[argc];
	    --argc;
	  }

	execvp (shell, new_argv);
	if (errno == ENOENT)
	  error ("%s: Shell program not found", shell);
	else
	  perror_with_name ("execvp: ", shell);
	break;
      }

    default:
      perror_with_name ("execvp: ", argv[0]);
      break;
    }

  _exit (127);
}

/* Figure out the argument list necessary to run LINE as a command.  Try to
   avoid using a shell.  This routine handles only ' quoting, and " quoting
   when no backslash, $ or ` characters are seen in the quotes.  Starting
   quotes may be escaped with a backslash.  If any of the characters in
   sh_chars[] is seen, or any of the builtin commands listed in sh_cmds[]
   is the first word of a line, the shell is used.

   If RESTP is not NULL, *RESTP is set to point to the first newline in LINE.
   If *RESTP is NULL, newlines will be ignored.

   SHELL is the shell to use, or nil to use the default shell.
   IFS is the value of $IFS, or nil (meaning the default).  */

static char **
construct_command_argv_internal (line, restp, shell, ifs)
     char *line, **restp;
     char *shell, *ifs;
{
#ifdef __MSDOS__
  static char sh_chars[] = "\"|<>";
  static char *sh_cmds[] = { "break", "call", "cd", "chcp", "chdir", "cls",
			     "copy", "ctty", "date", "del", "dir", "echo",
			     "erase", "exit", "for", "goto", "if", "if", "md",
			     "mkdir", "path", "pause", "prompt", "rem", "ren",
			     "rename", "set", "shift", "time", "type",
			     "ver", "verify", "vol", ":", 0 };
#else
  static char sh_chars[] = "#;\"*?[]&|<>(){}$`^";
  static char *sh_cmds[] = { "cd", "eval", "exec", "exit", "login",
			     "logout", "set", "umask", "wait", "while", "for",
			     "case", "if", ":", ".", "break", "continue",
			     "export", "read", "readonly", "shift", "times",
			     "trap", "switch", 0 };
#endif
  register int i;
  register char *p;
  register char *ap;
  char *end;
  int instring, word_has_equals, seen_nonequals;
  char **new_argv = 0;

  if (restp != NULL)
    *restp = NULL;

  /* Make sure not to bother processing an empty line.  */
  while (isblank (*line))
    ++line;
  if (*line == '\0')
    return 0;

  /* See if it is safe to parse commands internally.  */
  if (shell == 0)
    shell = default_shell;
  else if (strcmp (shell, default_shell))
    goto slow;

  if (ifs != 0)
    for (ap = ifs; *ap != '\0'; ++ap)
      if (*ap != ' ' && *ap != '\t' && *ap != '\n')
	goto slow;

  i = strlen (line) + 1;

  /* More than 1 arg per character is impossible.  */
  new_argv = (char **) xmalloc (i * sizeof (char *));

  /* All the args can fit in a buffer as big as LINE is.   */
  ap = new_argv[0] = (char *) xmalloc (i);
  end = ap + i;

  /* I is how many complete arguments have been found.  */
  i = 0;
  instring = word_has_equals = seen_nonequals = 0;
  for (p = line; *p != '\0'; ++p)
    {
      if (ap > end)
	abort ();

      if (instring)
	{
	string_char:
	  /* Inside a string, just copy any char except a closing quote
	     or a backslash-newline combination.  */
	  if (*p == instring)
	    instring = 0;
	  else if (*p == '\\' && p[1] == '\n')
	    goto swallow_escaped_newline;
	  else if (*p == '\n' && restp != NULL)
	    {
	      /* End of the command line.  */
	      *restp = p;
	      goto end_of_line;
	    }
	  /* Backslash, $, and ` are special inside double quotes.
	     If we see any of those, punt.  */
	  else if (instring == '"' && index ("\\$`", *p) != 0)
	    goto slow;
	  else
	    *ap++ = *p;
	}
      else if (index (sh_chars, *p) != 0)
	/* Not inside a string, but it's a special char.  */
	goto slow;
      else
	/* Not a special char.  */
	switch (*p)
	  {
	  case '=':
	    /* Equals is a special character in leading words before the
	       first word with no equals sign in it.  This is not the case
	       with sh -k, but we never get here when using nonstandard
	       shell flags.  */
	    if (! seen_nonequals)
	      goto slow;
	    word_has_equals = 1;
	    *ap++ = '=';
	    break;

	  case '\\':
	    /* Backslash-newline combinations are eaten.  */
	    if (p[1] == '\n')
	      {
	      swallow_escaped_newline:

		/* Eat the backslash, the newline, and following whitespace,
		   replacing it all with a single space.  */
		p += 2;

		/* If there is a tab after a backslash-newline,
		   remove it from the source line which will be echoed,
		   since it was most likely used to line
		   up the continued line with the previous one.  */
		if (*p == '\t')
		  strcpy (p, p + 1);

		if (instring)
		  goto string_char;
		else
		  {
		    if (ap != new_argv[i])
		      /* Treat this as a space, ending the arg.
			 But if it's at the beginning of the arg, it should
			 just get eaten, rather than becoming an empty arg. */
		      goto end_of_arg;
		    else
		      p = next_token (p) - 1;
		  }
	      }
	    else if (p[1] != '\0')
	      /* Copy and skip the following char.  */
	      *ap++ = *++p;
	    break;

	  case '\'':
	  case '"':
	    instring = *p;
	    break;

	  case '\n':
	    if (restp != NULL)
	      {
		/* End of the command line.  */
		*restp = p;
		goto end_of_line;
	      }
	    else
	      /* Newlines are not special.  */
	      *ap++ = '\n';
	    break;

	  case ' ':
	  case '\t':
	  end_of_arg:
	    /* We have the end of an argument.
	       Terminate the text of the argument.  */
	    *ap++ = '\0';
	    new_argv[++i] = ap;

	    /* Update SEEN_NONEQUALS, which tells us if every word
	       heretofore has contained an `='.  */
	    seen_nonequals |= ! word_has_equals;
	    if (word_has_equals && ! seen_nonequals)
	      /* An `=' in a word before the first
		 word without one is magical.  */
	      goto slow;
	    word_has_equals = 0; /* Prepare for the next word.  */

	    /* If this argument is the command name,
	       see if it is a built-in shell command.
	       If so, have the shell handle it.  */
	    if (i == 1)
	      {
		register int j;
		for (j = 0; sh_cmds[j] != 0; ++j)
		  if (streq (sh_cmds[j], new_argv[0]))
		    goto slow;
	      }

	    /* Ignore multiple whitespace chars.  */
	    p = next_token (p);
	    /* Next iteration should examine the first nonwhite char.  */
	    --p;
	    break;

	  default:
	    *ap++ = *p;
	    break;
	  }
    }
 end_of_line:

  if (instring)
    /* Let the shell deal with an unterminated quote.  */
    goto slow;

  /* Terminate the last argument and the argument list.  */

  *ap = '\0';
  if (new_argv[i][0] != '\0')
    ++i;
  new_argv[i] = 0;

  if (i == 1)
    {
      register int j;
      for (j = 0; sh_cmds[j] != 0; ++j)
	if (streq (sh_cmds[j], new_argv[0]))
	  goto slow;
    }

  if (new_argv[0] == 0)
    /* Line was empty.  */
    return 0;
  else
    return new_argv;

 slow:;
  /* We must use the shell.  */

  if (new_argv != 0)
    {
      /* Free the old argument list we were working on.  */
      free (new_argv[0]);
      free (new_argv);
    }

#ifdef __MSDOS__
   {
     FILE *batch;
     dos_batch_file = 1;
     if (dos_bname == 0)
       {
	 dos_bname = tempnam (".", "mk");
	 for (i = 0; dos_bname[i] != '\0'; ++i)
	   if (dos_bname[i] == '/')
	     dos_bname[i] = '\\';
	 dos_bename = (char *) xmalloc (strlen (dos_bname) + 5);
	 strcpy (dos_bename, dos_bname);
	 strcat (dos_bname, ".bat");
	 strcat (dos_bename, ".err");
       }
     batch = fopen (dos_bename, "w"); /* Create a file.  */
     if (batch != NULL)
       fclose (batch);
     batch = fopen (dos_bname, "w");
     fputs ("@echo off\n", batch);
     fputs (line, batch);
     fprintf (batch, "\nif errorlevel 1 del %s\n", dos_bename);
     fclose (batch);
     new_argv = (char **) xmalloc(2 * sizeof(char *));
     new_argv[0] = strdup (dos_bname);
     new_argv[1] = 0;
   }
#else	/* Not MSDOS.  */
  {
    /* SHELL may be a multi-word command.  Construct a command line
       "SHELL -c LINE", with all special chars in LINE escaped.
       Then recurse, expanding this command line to get the final
       argument list.  */
    
    unsigned int shell_len = strlen (shell);
    static char minus_c[] = " -c ";
    unsigned int line_len = strlen (line);
    
    char *new_line = (char *) alloca (shell_len + (sizeof (minus_c) - 1)
				      + (line_len * 2) + 1);
    
    ap = new_line;
    bcopy (shell, ap, shell_len);
    ap += shell_len;
    bcopy (minus_c, ap, sizeof (minus_c) - 1);
    ap += sizeof (minus_c) - 1;
    for (p = line; *p != '\0'; ++p)
      {
	if (restp != NULL && *p == '\n')
	  {
	    *restp = p;
	    break;
	  }
	else if (*p == '\\' && p[1] == '\n')
	  {
	    /* Eat the backslash, the newline, and following whitespace,
	       replacing it all with a single space (which is escaped
	       from the shell).  */
	    p += 2;

	    /* If there is a tab after a backslash-newline,
	       remove it from the source line which will be echoed,
	       since it was most likely used to line
	       up the continued line with the previous one.  */
	    if (*p == '\t')
	      strcpy (p, p + 1);

	    p = next_token (p);
	    --p;
	    *ap++ = '\\';
	    *ap++ = ' ';
	    continue;
	  }

	if (*p == '\\' || *p == '\'' || *p == '"'
	    || isspace (*p)
	    || index (sh_chars, *p) != 0)
	  *ap++ = '\\';
	*ap++ = *p;
      }
    *ap = '\0';
    
    new_argv = construct_command_argv_internal (new_line, (char **) NULL,
						(char *) 0, (char *) 0);
  }
#endif	/* MSDOS.  */

  return new_argv;
}

/* Figure out the argument list necessary to run LINE as a command.  Try to
   avoid using a shell.  This routine handles only ' quoting, and " quoting
   when no backslash, $ or ` characters are seen in the quotes.  Starting
   quotes may be escaped with a backslash.  If any of the characters in
   sh_chars[] is seen, or any of the builtin commands listed in sh_cmds[]
   is the first word of a line, the shell is used.

   If RESTP is not NULL, *RESTP is set to point to the first newline in LINE.
   If *RESTP is NULL, newlines will be ignored.

   FILE is the target whose commands these are.  It is used for
   variable expansion for $(SHELL) and $(IFS).  */

char **
construct_command_argv (line, restp, file)
     char *line, **restp;
     struct file *file;
{
  char *shell, *ifs;
  char **argv;

  {
    /* Turn off --warn-undefined-variables while we expand SHELL and IFS.  */
    int save = warn_undefined_variables_flag;
    warn_undefined_variables_flag = 0;

    shell = allocated_variable_expand_for_file ("$(SHELL)", file);
    ifs = allocated_variable_expand_for_file ("$(IFS)", file);

    warn_undefined_variables_flag = save;
  }

  argv = construct_command_argv_internal (line, restp, shell, ifs);

  free (shell);
  free (ifs);

  return argv;
}

#ifndef	HAVE_DUP2
int
dup2 (old, new)
     int old, new;
{
  int fd;

  (void) close (new);
  fd = dup (old);
  if (fd != new)
    {
      (void) close (fd);
      errno = EMFILE;
      return -1;
    }

  return fd;
}
#endif