about summary refs log tree commit diff
path: root/Src/Modules/system.c
blob: 9fd4d2583d69635cc0a685795279bf40d39512a1 (plain) (blame)
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
/*
 * sysread.c - interface to system read/write
 *
 * This file is part of zsh, the Z shell.
 *
 * Copyright (c) 1998-2003 Peter Stephenson
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and to distribute modified versions of this software for any
 * purpose, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 *
 * In no event shall Peter Stephenson or the Zsh Development
 * Group be liable to any party for direct, indirect, special, incidental,
 * or consequential damages arising out of the use of this software and
 * its documentation, even if Peter Stephenson, and the Zsh
 * Development Group have been advised of the possibility of such damage.
 *
 * Peter Stephenson and the Zsh Development Group specifically
 * disclaim any warranties, including, but not limited to, the implied
 * warranties of merchantability and fitness for a particular purpose.  The
 * software provided hereunder is on an "as is" basis, and Peter Stephenson
 * and the Zsh Development Group have no obligation to provide maintenance,
 * support, updates, enhancements, or modifications.
 *
 */

#include "system.mdh"
#include "system.pro"

#ifdef HAVE_POLL_H
# include <poll.h>
#endif
#if defined(HAVE_POLL) && !defined(POLLIN)
# undef HAVE_POLL
#endif

#define SYSREAD_BUFSIZE	8192

/**/
static int
getposint(char *instr, char *nam)
{
    char *eptr;
    int ret;

    ret = (int)zstrtol(instr, &eptr, 10);
    if (*eptr || ret < 0) {
	zwarnnam(nam, "integer expected: %s", instr);
	return -1;
    }

    return ret;
}


/*
 * Return values of bin_sysread:
 *	0	Successfully read (and written if appropriate)
 *	1	Error in parameters to command
 *	2	Error on read, or polling read fd ) ERRNO set by
 *      3	Error on write			  ) system
 *	4	Timeout on read
 *	5       Zero bytes read, end of file
 */

/**/
static int
bin_sysread(char *nam, char **args, Options ops, UNUSED(int func))
{
    int infd = 0, outfd = -1, bufsize = SYSREAD_BUFSIZE, count;
    char *outvar = NULL, *countvar = NULL, *inbuf;

    /* -i: input file descriptor if not stdin */
    if (OPT_ISSET(ops, 'i')) {
	infd = getposint(OPT_ARG(ops, 'i'), nam);
	if (infd < 0)
	    return 1;
    }

    /* -o: output file descriptor, else store in REPLY */
    if (OPT_ISSET(ops, 'o')) {
	if (*args) {
	    zwarnnam(nam, "no argument allowed with -o");
	    return 1;
	}
	outfd = getposint(OPT_ARG(ops, 'o'), nam);
	if (outfd < 0)
	    return 1;
    }

    /* -s: buffer size if not default SYSREAD_BUFSIZE */
    if (OPT_ISSET(ops, 's')) {
	bufsize = getposint(OPT_ARG(ops, 's'), nam);
	if (bufsize < 0)
	    return 1;
    }

    /* -c: name of variable to store count of transferred bytes */
    if (OPT_ISSET(ops, 'c')) {
	countvar = OPT_ARG(ops, 'c');
	if (!isident(countvar)) {
	    zwarnnam(nam, "not an identifier: %s", countvar);
	    return 1;
	}
    }

    if (*args) {
	/*
	 * Variable in which to store result if doing a plain read.
	 * Default variable if not specified is REPLY.
	 * If writing, only stuff we couldn't write is stored here,
	 * no default in that case (we just discard it if no variable).
	 */
	outvar = *args;
	if (!isident(outvar)) {
	    zwarnnam(nam, "not an identifier: %s", outvar);
	    return 1;
	}
    }

    inbuf = zhalloc(bufsize);

#if defined(HAVE_POLL) || defined(HAVE_SELECT)
    /* -t: timeout */
    if (OPT_ISSET(ops, 't'))
    {
# ifdef HAVE_POLL
	struct pollfd poll_fd;
	mnumber to_mn;
	int to_int, ret;

	poll_fd.fd = infd;
	poll_fd.events = POLLIN;

	to_mn = matheval(OPT_ARG(ops, 't'));
	if (errflag)
	    return 1;
	if (to_mn.type == MN_FLOAT)
	    to_int = (int) (1000 * to_mn.u.d);
	else
	    to_int = 1000 * (int)to_mn.u.l;

	while ((ret = poll(&poll_fd, 1, to_int)) < 0) {
	    if (errno != EINTR || errflag || retflag || breaks || contflag)
		break;
	}
	if (ret <= 0) {
	    /* treat non-timeout error as error on read */
	    return ret ? 2 : 4;
	}
# else
	/* using select */
	struct timeval select_tv;
	fd_set fds;
	mnumber to_mn;
	int ret;

	FD_ZERO(&fds);
	FD_SET(infd, &fds);
	to_mn = matheval(OPT_ARG(ops, 't'));
	if (errflag)
	    return 1;

	if (to_mn.type == MN_FLOAT) {
	    select_tv.tv_sec = (int) to_mn.u.d;
	    select_tv.tv_usec =
		(int) ((to_mn.u.d - select_tv.tv_sec) * 1e6);
	} else {
	    select_tv.tv_sec = (int) to_mn.u.l;
	    select_tv.tv_usec = 0;
	}

	while ((ret = select(infd+1, (SELECT_ARG_2_T) &fds,
			     NULL, NULL,&select_tv)) < 1) {
	    if (errno != EINTR || errflag || retflag || breaks || contflag)
		break;
	}
	if (ret <= 0) {
	    /* treat non-timeout error as error on read */
	    return ret ? 2 : 4;
	}
# endif
    }
#endif

    while ((count = read(infd, inbuf, bufsize)) < 0) {
	if (errno != EINTR || errflag || retflag || breaks || contflag)
	    break;
    }
    if (countvar)
	setiparam(countvar, count);
    if (count < 0)
	return 2;

    if (outfd >= 0) {
	if (!count)
	    return 5;
	while (count > 0) {
	    int ret;

	    ret = write(outfd, inbuf, count);
	    if (ret < 0) {
		if (errno == EINTR && !errflag &&
		    !retflag && !breaks && !contflag)
		    continue;
		if (outvar)
		    setsparam(outvar, metafy(inbuf, count, META_DUP));
		if (countvar)
		    setiparam(countvar, count);
		return 3;
	    }
	    inbuf += ret;
	    count -= ret;
	}
	return 0;
    }

    if (!outvar)
	    outvar = "REPLY";
    /* do this even if we read zero bytes */
    setsparam(outvar, metafy(inbuf, count, META_DUP));

    return count ? 0 : 5;
}


/*
 * Return values of bin_syswrite:
 *	0	Successfully written
 *	1	Error in parameters to command
 *	2	Error on write, ERRNO set by system
 */

/**/
static int
bin_syswrite(char *nam, char **args, Options ops, UNUSED(int func))
{
    int outfd = 1, len, count, totcount;
    char *countvar = NULL;

    /* -o: output file descriptor if not stdout */
    if (OPT_ISSET(ops, 'o')) {
	outfd = getposint(OPT_ARG(ops, 'o'), nam);
	if (outfd < 0)
	    return 1;
    }

    /* -c: variable in which to store count of bytes written */
    if (OPT_ISSET(ops, 'c')) {
	countvar = OPT_ARG(ops, 'c');
	if (!isident(countvar)) {
	    zwarnnam(nam, "not an identifier: %s", countvar);
	    return 1;
	}
    }

    totcount = 0;
    unmetafy(*args, &len);
    while (len) {
	while ((count = write(outfd, *args, len)) < 0) {
	    if (errno != EINTR || errflag || retflag || breaks || contflag)
	    {
		if (countvar)
		    setiparam(countvar, totcount);
		return 2;
	    }
	}
	*args += count;
	totcount += count;
	len -= count;
    }
    if (countvar)
	setiparam(countvar, totcount);

    return 0;
}


static struct { char *name; int oflag; } openopts[] = {
#ifdef O_CLOEXEC
    { "cloexec", O_CLOEXEC },
#else
# ifdef FD_CLOEXEC
    { "cloexec", 0  }, /* this needs to be first in the table */
# endif
#endif
#ifdef O_NOFOLLOW
    { "nofollow", O_NOFOLLOW },
#endif
#ifdef O_SYNC
    { "sync", O_SYNC },
#endif
#ifdef O_NOATIME
    { "noatime", O_NOATIME },
#endif
    { "excl", O_EXCL | O_CREAT },
    { "creat", O_CREAT },
    { "create", O_CREAT },
    { "truncate", O_TRUNC },
    { "trunc", O_TRUNC }
};

/**/
static int
bin_sysopen(char *nam, char **args, Options ops, UNUSED(int func))
{
    int read = OPT_ISSET(ops, 'r');
    int write = OPT_ISSET(ops, 'w');
    int append = OPT_ISSET(ops, 'a') ? O_APPEND : 0;
    int flags = O_NOCTTY | append | ((append || write) ?
	(read ? O_RDWR : O_WRONLY) : O_RDONLY);
    char *opt, *ptr, *nextopt, *fdvar;
    int o, fd, moved_fd, explicit = -1;
    mode_t perms = 0666;
#if defined(FD_CLOEXEC) && !defined(O_CLOEXEC)
    int fdflags;
#endif

    if (!OPT_ISSET(ops, 'u')) {
	zwarnnam(nam, "file descriptor not specified");
	return 1;
    }

    /* file descriptor, either 0-9 or a variable name */
    fdvar = OPT_ARG(ops, 'u');
    if (idigit(*fdvar) && !fdvar[1]) {
	explicit = atoi(fdvar);
    } else if (!isident(fdvar)) {
	zwarnnam(nam, "not an identifier: %s", fdvar);
	return 1;
    }

    /* open options */
    if (OPT_ISSET(ops, 'o')) {
	opt = OPT_ARG(ops, 'o');
	while (opt) {
	    if (!strncasecmp(opt, "O_", 2)) /* ignore initial O_ */
		opt += 2;
	    if ((nextopt = strchr(opt, ',')))
		*nextopt++ = '\0';
	    for (o = sizeof(openopts)/sizeof(*openopts) - 1; o >= 0 &&
		strcasecmp(openopts[o].name, opt); o--) {}
	    if (o < 0) {
		zwarnnam(nam, "unsupported option: %s\n", opt);
		return 1;
	    }
#if defined(FD_CLOEXEC) && !defined(O_CLOEXEC)
	    if (!openopts[o].oflag)
		fdflags = FD_CLOEXEC;
#endif
	    flags |= openopts[o].oflag;
	    opt = nextopt;
	}
    }

    /* -m: permissions or mode for created files */
    if (OPT_ISSET(ops, 'm')) {
	ptr = opt = OPT_ARG(ops, 'm');
	while (*ptr >= '0' && *ptr <= '7') ptr++;
	if (*ptr || ptr - opt < 3) {
	    zwarnnam(nam, "invalid mode %s", opt);
	    return 1;
	}
	perms = zstrtol(opt, 0, 8); /* octal number */
    }

    if (flags & O_CREAT)
	fd = open(*args, flags, perms);
    else
	fd = open(*args, flags);

    if (fd == -1) {
	zwarnnam(nam, "can't open file %s: %e", *args, errno);
	return 1;
    }
    moved_fd = (explicit > -1) ? redup(fd, explicit) : movefd(fd);
    if (moved_fd == -1) {
	zwarnnam(nam, "can't open file %s", *args);
	return 1;
    }

#ifdef FD_CLOEXEC
#ifdef O_CLOEXEC
    /*
     * the O_CLOEXEC is a flag attached to the *file descriptor*, not the
     * *open file description* so it doesn't survive a dup(). If that flag was
     * requested and the fd was moved, we need to reapply it to the moved fd
     * even if the original one was open with O_CLOEXEC
     */
    if ((flags & O_CLOEXEC) && fd != moved_fd)
#else
    if (fdflags)
#endif /* O_CLOEXEC */
	fcntl(moved_fd, F_SETFD, FD_CLOEXEC);
#endif /* FD_CLOEXEC */
    if (explicit == -1) {
	fdtable[moved_fd] = FDT_EXTERNAL;
	setiparam(fdvar, moved_fd);
	/* if setting the variable failed, close moved_fd to avoid leak */
	if (errflag)
	    zclose(moved_fd);
    }

    return 0;
}


/*
 * Return values of bin_sysseek:
 *	0	Success
 *	1	Error in parameters to command
 *	2	Error on seek, ERRNO set by system
 */

/**/
static int
bin_sysseek(char *nam, char **args, Options ops, UNUSED(int func))
{
    int w = SEEK_SET, fd = 0;
    char *whence;
    off_t pos;

    /* -u:  file descriptor if not stdin */
    if (OPT_ISSET(ops, 'u')) {
	fd = getposint(OPT_ARG(ops, 'u'), nam);
	if (fd < 0)
	    return 1;
    }

    /* -w:  whence - starting point of seek */
    if (OPT_ISSET(ops, 'w')) {
	whence = OPT_ARG(ops, 'w');
        if (!(strcasecmp(whence, "current") && strcmp(whence, "1")))
	    w = SEEK_CUR;
        else if (!(strcasecmp(whence, "end") && strcmp(whence, "2")))
	    w = SEEK_END;
	else if (strcasecmp(whence, "start") && strcmp(whence, "0")) {
	    zwarnnam(nam, "unknown argument to -w: %s", whence);
	    return 1;
	}
    }

    pos = (off_t)mathevali(*args);
    return (lseek(fd, pos, w) == -1) ? 2 : 0;
}

/**/
static mnumber
math_systell(UNUSED(char *name), UNUSED(int argc), mnumber *argv, UNUSED(int id))
{
    int fd = (argv->type == MN_INTEGER) ? argv->u.l : (int)argv->u.d;
    mnumber ret;
    ret.type = MN_INTEGER;
    ret.u.l = 0;

    if (fd < 0) {
	zerr("file descriptor out of range");
	return ret;
    }
    ret.u.l = lseek(fd, 0, SEEK_CUR);
    return ret;
}


/*
 * Return values of bin_syserror:
 *	0	Successfully processed error
 *		(although if the number was invalid the string
 *		may not be useful)
 *	1	Error in parameters
 *	2	Name of error not recognised.
 */

/**/
static int
bin_syserror(char *nam, char **args, Options ops, UNUSED(int func))
{
    int num = 0;
    char *errvar = NULL, *msg, *pfx = "", *str;

    /* variable in which to write error message */
    if (OPT_ISSET(ops, 'e')) {
	errvar = OPT_ARG(ops, 'e');
	if (!isident(errvar)) {
	    zwarnnam(nam, "not an identifier: %s", errvar);
	    return 1;
	}
    }
    /* prefix for error message */
    if (OPT_ISSET(ops, 'p'))
	pfx = OPT_ARG(ops, 'p');

    if (!*args)
	num = errno;
    else {
	char *ptr = *args;
	while (*ptr && idigit(*ptr))
	    ptr++;
	if (!*ptr && ptr > *args)
	    num = atoi(*args);
	else {
	    const char **eptr;
	    for (eptr = sys_errnames; *eptr; eptr++) {
		if (!strcmp(*eptr, *args)) {
		    num = (eptr - sys_errnames) + 1;
		    break;
		}
	    }
	    if (!*eptr)
		return 2;
	}
    }

    msg = strerror(num);
    if (errvar) {
	str = (char *)zalloc(strlen(msg) + strlen(pfx) + 1);
	sprintf(str, "%s%s", pfx, msg);
	setsparam(errvar, str);
    } else {
	fprintf(stderr, "%s%s\n", pfx, msg);
    }

    return 0;
}

/**/
static int
bin_zsystem_flock(char *nam, char **args, UNUSED(Options ops), UNUSED(int func))
{
    int cloexec = 1, unlock = 0, readlock = 0;
    zlong timeout = -1;
    char *fdvar = NULL;
#ifdef HAVE_FCNTL_H
    struct flock lck;
    int flock_fd, flags;
#endif

    while (*args && **args == '-') {
	int opt;
	char *optptr = *args + 1, *optarg;
	args++;
	if (!*optptr || !strcmp(optptr, "-"))
	    break;
	while ((opt = *optptr)) {
	    switch (opt) {
	    case 'e':
		/* keep lock on "exec" */
		cloexec = 0;
		break;

	    case 'f':
		/* variable for fd */
		if (optptr[1]) {
		    fdvar = optptr + 1;
		    optptr += strlen(fdvar) - 1;
		} else if (*args) {
		    fdvar = *args++;
		}
		if (fdvar == NULL || !isident(fdvar)) {
		    zwarnnam(nam, "flock: option %c requires a variable name",
			     opt);
		    return 1;
		}
		break;

	    case 'r':
		/* read lock rather than read-write lock */
		readlock = 1;
		break;

	    case 't':
		/* timeout in seconds */
		if (optptr[1]) {
		    optarg = optptr + 1;
		    optptr += strlen(optarg) - 1;
		} else if (!*args) {
		    zwarnnam(nam, "flock: option %c requires a numeric timeout",
			     opt);
		    return 1;
		} else {
		    optarg = *args++;
		}
		timeout = mathevali(optarg);
		break;

	    case 'u':
		/* unlock: argument is fd */
		unlock = 1;
		break;

	    default:
		zwarnnam(nam, "flock: unknown option: %c", *optptr);
		return 1;
	    }
	    optptr++;
	}
    }


    if (!args[0]) {
	zwarnnam(nam, "flock: not enough arguments");
	return 1;
    }
    if (args[1]) {
	zwarnnam(nam, "flock: too many arguments");
	return 1;
    }

#ifdef HAVE_FCNTL_H
    if (unlock) {
	flock_fd = (int)mathevali(args[0]);
	if (zcloselockfd(flock_fd) < 0) {
	    zwarnnam(nam, "flock: file descriptor %d not in use for locking",
		     flock_fd);
	    return 1;
	}
	return 0;
    }

    if (readlock)
	flags = O_RDONLY | O_NOCTTY;
    else
	flags = O_RDWR | O_NOCTTY;
    if ((flock_fd = open(unmeta(args[0]), flags)) < 0) {
	zwarnnam(nam, "failed to open %s for writing: %e", args[0], errno);
	return 1;
    }
    flock_fd = movefd(flock_fd);
    if (flock_fd == -1)
	return 1;
#ifdef FD_CLOEXEC
    if (cloexec)
    {
	long fdflags = fcntl(flock_fd, F_GETFD, 0);
	if (fdflags != (long)-1)
	    fcntl(flock_fd, F_SETFD, fdflags | FD_CLOEXEC);
    }
#endif
    addlockfd(flock_fd, cloexec);

    lck.l_type = readlock ? F_RDLCK : F_WRLCK;
    lck.l_whence = SEEK_SET;
    lck.l_start = 0;
    lck.l_len = 0;  /* lock the whole file */

    if (timeout > 0) {
	time_t end = time(NULL) + (time_t)timeout;
	while (fcntl(flock_fd, F_SETLK, &lck) < 0) {
	    if (errflag) {
                zclose(flock_fd);
		return 1;
            }
	    if (errno != EINTR && errno != EACCES && errno != EAGAIN) {
                zclose(flock_fd);
		zwarnnam(nam, "failed to lock file %s: %e", args[0], errno);
		return 1;
	    }
	    if (time(NULL) >= end) {
                zclose(flock_fd);
		return 2;
            }
	    sleep(1);
	}
    } else {
	while (fcntl(flock_fd, timeout == 0 ? F_SETLK : F_SETLKW, &lck) < 0) {
	    if (errflag) {
                zclose(flock_fd);
		return 1;
            }
	    if (errno == EINTR)
		continue;
            zclose(flock_fd);
	    zwarnnam(nam, "failed to lock file %s: %e", args[0], errno);
	    return 1;
	}
    }

    if (fdvar)
	setiparam(fdvar, flock_fd);

    return 0;
#else /* HAVE_FCNTL_H */
    zwarnnam(nam, "flock: not implemented on this system");
    return 255;
#endif /* HAVE_FCNTL_H */
}


/*
 * Return status zero if the zsystem feature is supported, else 1.
 * Operates silently for future-proofing.
 */
/**/
static int
bin_zsystem_supports(char *nam, char **args,
		     UNUSED(Options ops), UNUSED(int func))
{
    if (!args[0]) {
	zwarnnam(nam, "supports: not enough arguments");
	return 255;
    }
    if (args[1]) {
	zwarnnam(nam, "supports: too many arguments");
	return 255;
    }

    /* stupid but logically this should work... */
    if (!strcmp(*args, "supports"))
	return 0;
#ifdef HAVE_FCNTL_H
    if (!strcmp(*args, "flock"))
	return 0;
#endif
    return 1;
}


/**/
static int
bin_zsystem(char *nam, char **args, Options ops, int func)
{
    /* If more commands are implemented, this can be more sophisticated */
    if (!strcmp(*args, "flock")) {
	return bin_zsystem_flock(nam, args+1, ops, func);
    } else if (!strcmp(*args, "supports")) {
	return bin_zsystem_supports(nam, args+1, ops, func);
    }
    zwarnnam(nam, "unknown subcommand: %s", *args);
    return 1;
}

static struct builtin bintab[] = {
    BUILTIN("syserror", 0, bin_syserror, 0, 1, 0, "e:p:", NULL),
    BUILTIN("sysread", 0, bin_sysread, 0, 1, 0, "c:i:o:s:t:", NULL),
    BUILTIN("syswrite", 0, bin_syswrite, 1, 1, 0, "c:o:", NULL),
    BUILTIN("sysopen", 0, bin_sysopen, 1, 1, 0, "rwau:o:m:", NULL),
    BUILTIN("sysseek", 0, bin_sysseek, 1, 1, 0, "u:w:", NULL),
    BUILTIN("zsystem", 0, bin_zsystem, 1, -1, 0, NULL, NULL)
};


/* Functions for the errnos special parameter. */

/**/
static char **
errnosgetfn(UNUSED(Param pm))
{
    /* arrdup etc. should really take const pointers as arguments */
    return arrdup((char **)sys_errnames);
}

static const struct gsu_array errnos_gsu =
{ errnosgetfn, arrsetfn, stdunsetfn };


/* Functions for the sysparams special parameter. */

/**/
static void
fillpmsysparams(Param pm, const char *name)
{
    char buf[DIGBUFSIZE];
    int num;

    pm->node.nam = dupstring(name);
    pm->node.flags = PM_SCALAR | PM_READONLY;
    pm->gsu.s = &nullsetscalar_gsu;
    if (!strcmp(name, "pid")) {
	num = (int)getpid();
    } else if (!strcmp(name, "ppid")) {
	num = (int)getppid();
    } else {
	pm->u.str = dupstring("");
	pm->node.flags |= PM_UNSET;
	return;
    }

    sprintf(buf, "%d", num);
    pm->u.str = dupstring(buf);
}


/**/
static HashNode
getpmsysparams(UNUSED(HashTable ht), const char *name)
{
    Param pm;

    pm = (Param) hcalloc(sizeof(struct param));
    fillpmsysparams(pm, name);
    return &pm->node;
}


/**/
static void
scanpmsysparams(UNUSED(HashTable ht), ScanFunc func, int flags)
{
    struct param spm;

    fillpmsysparams(&spm, "pid");
    func(&spm.node, flags);
    fillpmsysparams(&spm, "ppid");
    func(&spm.node, flags);
}

static struct mathfunc mftab[] = {
    NUMMATHFUNC("systell", math_systell, 1, 1, 0)
};

static struct paramdef partab[] = {
    SPECIALPMDEF("errnos", PM_ARRAY|PM_READONLY,
		 &errnos_gsu, NULL, NULL),
    SPECIALPMDEF("sysparams", PM_READONLY,
		 NULL, getpmsysparams, scanpmsysparams)
};

static struct features module_features = {
    bintab, sizeof(bintab)/sizeof(*bintab),
    NULL, 0,
    mftab, sizeof(mftab)/sizeof(*mftab),
    partab, sizeof(partab)/sizeof(*partab),
    0
};

/* The load/unload routines required by the zsh library interface */

/**/
int
setup_(UNUSED(Module m))
{
    return 0;
}

/**/
int
features_(Module m, char ***features)
{
    *features = featuresarray(m, &module_features);
    return 0;
}

/**/
int
enables_(Module m, int **enables)
{
    return handlefeatures(m, &module_features, enables);
}

/**/
int
boot_(UNUSED(Module m))
{
    return 0;
}


/**/
int
cleanup_(Module m)
{
    return setfeatureenables(m, &module_features, NULL);
}

/**/
int
finish_(UNUSED(Module m))
{
    return 0;
}