summaryrefslogtreecommitdiff
path: root/miscutils/crond.c
blob: 2e8ca8b680580e48812667c75b12af1bb482f28d (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
/* vi: set sw=4 ts=4: */
/*
 * run as root, but NOT setuid root
 *
 * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
 * (version 2.3.2)
 * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config CROND
//config:	bool "crond (14 kb)"
//config:	default y
//config:	select FEATURE_SYSLOG
//config:	help
//config:	Crond is a background daemon that parses individual crontab
//config:	files and executes commands on behalf of the users in question.
//config:	This is a port of dcron from slackware. It uses files of the
//config:	format /var/spool/cron/crontabs/<username> files, for example:
//config:		$ cat /var/spool/cron/crontabs/root
//config:		# Run daily cron jobs at 4:40 every day:
//config:		40 4 * * * /etc/cron/daily > /dev/null 2>&1
//config:
//config:config FEATURE_CROND_D
//config:	bool "Support -d (redirect output to stderr)"
//config:	depends on CROND
//config:	default y
//config:	help
//config:	-d N sets loglevel (0:most verbose) and directs all output to stderr.
//config:
//config:config FEATURE_CROND_CALL_SENDMAIL
//config:	bool "Report command output via email (using sendmail)"
//config:	default y
//config:	depends on CROND
//config:	help
//config:	Command output will be sent to corresponding user via email.
//config:
//config:config FEATURE_CROND_SPECIAL_TIMES
//config:	bool "Support special times (@reboot, @daily, etc) in crontabs"
//config:	default y
//config:	depends on CROND
//config:	help
//config:	string        meaning
//config:	------        -------
//config:	@reboot       Run once, at startup
//config:	@yearly       Run once a year:  "0 0 1 1 *"
//config:	@annually     Same as @yearly:  "0 0 1 1 *"
//config:	@monthly      Run once a month: "0 0 1 * *"
//config:	@weekly       Run once a week:  "0 0 * * 0"
//config:	@daily        Run once a day:   "0 0 * * *"
//config:	@midnight     Same as @daily:   "0 0 * * *"
//config:	@hourly       Run once an hour: "0 * * * *"
//config:
//config:config FEATURE_CROND_DIR
//config:	string "crond spool directory"
//config:	default "/var/spool/cron"
//config:	depends on CROND || CRONTAB
//config:	help
//config:	Location of crond spool.

//applet:IF_CROND(APPLET(crond, BB_DIR_USR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_CROND) += crond.o

//usage:#define crond_trivial_usage
//usage:       "-fbS -l N " IF_FEATURE_CROND_D("-d N ") "-L LOGFILE -c DIR"
//usage:#define crond_full_usage "\n\n"
//usage:       "	-f	Foreground"
//usage:     "\n	-b	Background (default)"
//usage:     "\n	-S	Log to syslog (default)"
//usage:     "\n	-l N	Set log level. Most verbose 0, default 8"
//usage:	IF_FEATURE_CROND_D(
//usage:     "\n	-d N	Set log level, log to stderr"
//usage:	)
//usage:     "\n	-L FILE	Log to FILE"
//usage:     "\n	-c DIR	Cron dir. Default:"CONFIG_FEATURE_CROND_DIR"/crontabs"

#include "libbb.h"
#include "common_bufsiz.h"
#include <syslog.h>

#if 0
/* If libc tracks and reuses setenv()-allocated memory, ok to set this to 0 */
/* Neither glibc nor uclibc do that! */
# define SETENV_LEAKS 0
#else
# define SETENV_LEAKS 1
#endif


#define CRON_DIR        CONFIG_FEATURE_CROND_DIR
#define CRONTABS        CONFIG_FEATURE_CROND_DIR "/crontabs"
#define CRON_REBOOT     CONFIG_PID_FILE_PATH "/crond.reboot"
#ifndef SENDMAIL
# define SENDMAIL       "sendmail"
#endif
#ifndef SENDMAIL_ARGS
# define SENDMAIL_ARGS  "-ti"
#endif
#ifndef CRONUPDATE
# define CRONUPDATE     "cron.update"
#endif
#ifndef MAXLINES
# define MAXLINES       256  /* max lines in non-root crontabs */
#endif


typedef struct CronFile {
	struct CronFile *cf_next;
	struct CronLine *cf_lines;
	char *cf_username;
	smallint cf_wants_starting;     /* bool: one or more jobs ready */
	smallint cf_has_running;        /* bool: one or more jobs running */
	smallint cf_deleted;            /* marked for deletion (but still has running jobs) */
} CronFile;

typedef struct CronLine {
	struct CronLine *cl_next;
	char *cl_cmd;                   /* shell command */
	pid_t cl_pid;                   /* >0:running, <0:needs to be started in this minute, 0:dormant */
#define START_ME_REBOOT -2
#define START_ME_NORMAL -1
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
	int cl_empty_mail_size;         /* size of mail header only, 0 if no mailfile */
	char *cl_mailto;                /* whom to mail results, may be NULL */
#endif
	char *cl_shell;
	/* ordered by size, not in natural order. makes code smaller: */
	char cl_Dow[7];                 /* 0-6, beginning sunday */
	char cl_Mons[12];               /* 0-11 */
	char cl_Hrs[24];                /* 0-23 */
	char cl_Days[32];               /* 1-31 */
	char cl_Mins[60];               /* 0-59 */
} CronLine;


#define DAEMON_UID 0


enum {
	OPT_l = (1 << 0),
	OPT_L = (1 << 1),
	OPT_f = (1 << 2),
	OPT_b = (1 << 3),
	OPT_S = (1 << 4),
	OPT_c = (1 << 5),
	OPT_d = (1 << 6) * ENABLE_FEATURE_CROND_D,
};

struct globals {
	unsigned log_level; /* = 8; */
	time_t crontab_dir_mtime;
	const char *log_filename;
	const char *crontab_dir_name; /* = CRONTABS; */
	CronFile *cron_files;
	char *default_shell;
#if SETENV_LEAKS
	char *env_var_user;
	char *env_var_home;
	char *env_var_shell;
	char *env_var_logname;
#endif
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { \
	setup_common_bufsiz(); \
	G.log_level = 8; \
	G.crontab_dir_name = CRONTABS; \
} while (0)

/* Log levels:
 * 0 is the most verbose, default 8.
 * For some reason, in fact only 5, 7 and 8 are used.
 */
static void crondlog(unsigned level, const char *msg, va_list va)
{
	if (level >= G.log_level) {
		/*
		 * We are called only for info meesages.
		 * Warnings/errors use plain bb_[p]error_msg's, which
		 * need not touch syslog_level
		 * (they are ok with LOG_ERR default).
		 */
		bb_vinfo_msg(msg, va);
	}
}

static void log5(const char *msg, ...)
{
	va_list va;
	va_start(va, msg);
	crondlog(4, msg, va);
	va_end(va);
}

static void log7(const char *msg, ...)
{
	va_list va;
	va_start(va, msg);
	crondlog(7, msg, va);
	va_end(va);
}

static void log8(const char *msg, ...)
{
	va_list va;
	va_start(va, msg);
	crondlog(8, msg, va);
	va_end(va);
}


static const char DowAry[] ALIGN1 =
	"sun""mon""tue""wed""thu""fri""sat"
;

static const char MonAry[] ALIGN1 =
	"jan""feb""mar""apr""may""jun""jul""aug""sep""oct""nov""dec"
;

static void ParseField(char *user, char *ary, int modvalue, int off,
				const char *names, char *ptr)
/* 'names' is a pointer to a set of 3-char abbreviations */
{
	char *base = ptr;
	int n1 = -1;
	int n2 = -1;

	// this can't happen due to config_read()
	/*if (base == NULL)
		return;*/

	while (1) {
		int skip = 0;

		/* Handle numeric digit or symbol or '*' */
		if (*ptr == '*') {
			n1 = 0;  /* everything will be filled */
			n2 = modvalue - 1;
			skip = 1;
			++ptr;
		} else if (isdigit(*ptr)) {
			char *endp;
			if (n1 < 0) {
				n1 = strtol(ptr, &endp, 10) + off;
			} else {
				n2 = strtol(ptr, &endp, 10) + off;
			}
			ptr = endp; /* gcc likes temp var for &endp */
			skip = 1;
		} else if (names) {
			int i;

			for (i = 0; names[i]; i += 3) {
				/* was using strncmp before... */
				if (strncasecmp(ptr, &names[i], 3) == 0) {
					ptr += 3;
					if (n1 < 0) {
						n1 = i / 3;
					} else {
						n2 = i / 3;
					}
					skip = 1;
					break;
				}
			}
		}

		/* handle optional range '-' */
		if (skip == 0) {
			goto err;
		}
		if (*ptr == '-' && n2 < 0) {
			++ptr;
			continue;
		}

		/*
		 * collapse single-value ranges, handle skipmark, and fill
		 * in the character array appropriately.
		 */
		if (n2 < 0) {
			n2 = n1;
		}
		if (*ptr == '/') {
			char *endp;
			skip = strtol(ptr + 1, &endp, 10);
			ptr = endp; /* gcc likes temp var for &endp */
		}

		/*
		 * fill array, using a failsafe is the easiest way to prevent
		 * an endless loop
		 */
		{
			int s0 = 1;
			int failsafe = 1024;

			--n1;
			do {
				n1 = (n1 + 1) % modvalue;

				if (--s0 == 0) {
					ary[n1 % modvalue] = 1;
					s0 = skip;
				}
				if (--failsafe == 0) {
					goto err;
				}
			} while (n1 != n2);
		}
		if (*ptr != ',') {
			break;
		}
		++ptr;
		n1 = -1;
		n2 = -1;
	}

	if (*ptr) {
 err:
		bb_error_msg("user %s: parse error at %s", user, base);
		return;
	}

	/* can't use log5 (it inserts newlines), open-coding it */
	if (G.log_level <= 5 && logmode != LOGMODE_SYSLOG) {
		int i;
		for (i = 0; i < modvalue; ++i)
			fprintf(stderr, "%d", (unsigned char)ary[i]);
		bb_putchar_stderr('\n');
	}
}

static void FixDayDow(CronLine *line)
{
	unsigned i;
	int weekUsed = 0;
	int daysUsed = 0;

	for (i = 0; i < ARRAY_SIZE(line->cl_Dow); ++i) {
		if (line->cl_Dow[i] == 0) {
			weekUsed = 1;
			break;
		}
	}
	for (i = 0; i < ARRAY_SIZE(line->cl_Days); ++i) {
		if (line->cl_Days[i] == 0) {
			daysUsed = 1;
			break;
		}
	}
	if (weekUsed != daysUsed) {
		if (weekUsed)
			memset(line->cl_Days, 0, sizeof(line->cl_Days));
		else /* daysUsed */
			memset(line->cl_Dow, 0, sizeof(line->cl_Dow));
	}
}

/*
 * delete_cronfile() - delete user database
 *
 * Note: multiple entries for same user may exist if we were unable to
 * completely delete a database due to running processes.
 */
//FIXME: we will start a new job even if the old job is running
//if crontab was reloaded: crond thinks that "new" job is different from "old"
//even if they are in fact completely the same. Example
//Crontab was:
// 0-59 * * * * job1
// 0-59 * * * * long_running_job2
//User edits crontab to:
// 0-59 * * * * job1_updated
// 0-59 * * * * long_running_job2
//Bug: crond can now start another long_running_job2 even if old one
//is still running.
//OTOH most other versions of cron do not wait for job termination anyway,
//they end up with multiple copies of jobs if they don't terminate soon enough.
static void delete_cronfile(const char *userName)
{
	CronFile **pfile = &G.cron_files;
	CronFile *file;

	while ((file = *pfile) != NULL) {
		if (strcmp(userName, file->cf_username) == 0) {
			CronLine **pline = &file->cf_lines;
			CronLine *line;

			file->cf_has_running = 0;
			file->cf_deleted = 1;

			while ((line = *pline) != NULL) {
				if (line->cl_pid > 0) {
					file->cf_has_running = 1;
					pline = &line->cl_next;
				} else {
					*pline = line->cl_next;
					free(line->cl_cmd);
					free(line);
				}
			}
			if (file->cf_has_running == 0) {
				*pfile = file->cf_next;
				free(file->cf_username);
				free(file);
				continue;
			}
		}
		pfile = &file->cf_next;
	}
}

static void load_crontab(const char *fileName)
{
	struct parser_t *parser;
	struct stat sbuf;
	int maxLines;
	char *tokens[6];
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
	char *mailTo = NULL;
#endif
	char *shell = NULL;

	delete_cronfile(fileName);

	if (!getpwnam(fileName)) {
		log7("ignoring file '%s' (no such user)", fileName);
		return;
	}

	parser = config_open(fileName);
	if (!parser)
		return;

	maxLines = (strcmp(fileName, "root") == 0) ? 65535 : MAXLINES;

	if (fstat(fileno(parser->fp), &sbuf) == 0 && sbuf.st_uid == DAEMON_UID) {
		CronFile *file = xzalloc(sizeof(CronFile));
		CronLine **pline;
		int n;

		file->cf_username = xstrdup(fileName);
		pline = &file->cf_lines;

		while (1) {
			CronLine *line;

			if (!--maxLines) {
				bb_error_msg("user %s: too many lines", fileName);
				break;
			}

			n = config_read(parser, tokens, 6, 1, "# \t", PARSE_NORMAL | PARSE_KEEP_COPY);
			if (!n)
				break;

			log5("user:%s entry:%s", fileName, parser->data);

			/* check if line is setting MAILTO= */
			if (is_prefixed_with(tokens[0], "MAILTO=")) {
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
				free(mailTo);
				mailTo = (tokens[0][7]) ? xstrdup(&tokens[0][7]) : NULL;
#endif /* otherwise just ignore such lines */
				continue;
			}
			if (is_prefixed_with(tokens[0], "SHELL=")) {
				free(shell);
				shell = xstrdup(&tokens[0][6]);
				continue;
			}
//TODO: handle HOME= too? "man crontab" says:
//name = value
//
//where the spaces around the equal-sign (=) are optional, and any subsequent
//non-leading spaces in value will be part of the value assigned to name.
//The value string may be placed in quotes (single or double, but matching)
//to preserve leading or trailing blanks.
//
//Several environment variables are set up automatically by the cron(8) daemon.
//SHELL is set to /bin/sh, and LOGNAME and HOME are set from the /etc/passwd
//line of the crontab's owner. HOME and SHELL may be overridden by settings
//in the crontab; LOGNAME may not.

#if ENABLE_FEATURE_CROND_SPECIAL_TIMES
			if (tokens[0][0] == '@') {
				/*
				 * "@daily /a/script/to/run PARAM1 PARAM2..."
				 */
				typedef struct SpecialEntry {
					const char *name;
					const char tokens[8];
				} SpecialEntry;
				static const SpecialEntry SpecAry[] = {
					/*              hour  day   month weekday */
					{ "yearly",     "0\0" "1\0" "1\0" "*" },
					{ "annually",   "0\0" "1\0" "1\0" "*" },
					{ "monthly",    "0\0" "1\0" "*\0" "*" },
					{ "weekly",     "0\0" "*\0" "*\0" "0" },
					{ "daily",      "0\0" "*\0" "*\0" "*" },
					{ "midnight",   "0\0" "*\0" "*\0" "*" },
					{ "hourly",     "*\0" "*\0" "*\0" "*" },
					{ "reboot",     ""                    },
				};
				const SpecialEntry *e = SpecAry;

				if (n < 2)
					continue;
				for (;;) {
					if (strcmp(e->name, tokens[0] + 1) == 0) {
						/*
						 * tokens[1] is only the first word of command,
						 * can'r use it.
						 * find the entire command in unmodified string:
						 */
						tokens[5] = skip_whitespace(
							skip_non_whitespace(
							skip_whitespace(parser->data)));
						if (e->tokens[0]) {
							char *et = (char*)e->tokens;
							/* minute is "0" for all specials */
							tokens[0] = (char*)"0";
							tokens[1] = et;
							tokens[2] = et + 2;
							tokens[3] = et + 4;
							tokens[4] = et + 6;
						}
						goto got_it;
					}
					if (!e->tokens[0])
						break;
					e++;
				}
				continue; /* bad line (unrecognized '@foo') */
			}
#endif
			/* check if a minimum of tokens is specified */
			if (n < 6)
				continue;
 IF_FEATURE_CROND_SPECIAL_TIMES(
  got_it:
 )
			*pline = line = xzalloc(sizeof(*line));
#if ENABLE_FEATURE_CROND_SPECIAL_TIMES
			if (tokens[0][0] == '@') { /* "@reboot" line */
				file->cf_wants_starting = 1;
				line->cl_pid = START_ME_REBOOT; /* wants to start */
				/* line->cl_Mins/Hrs/etc stay zero: never match any time */
			} else
#endif
			{
				/* parse date ranges */
				ParseField(file->cf_username, line->cl_Mins, 60, 0, NULL, tokens[0]);
				ParseField(file->cf_username, line->cl_Hrs, 24, 0, NULL, tokens[1]);
				ParseField(file->cf_username, line->cl_Days, 32, 0, NULL, tokens[2]);
				ParseField(file->cf_username, line->cl_Mons, 12, -1, MonAry, tokens[3]);
				ParseField(file->cf_username, line->cl_Dow, 7, 0, DowAry, tokens[4]);
				/*
				 * fix days and dow - if one is not "*" and the other
				 * is "*", the other is set to 0, and vise-versa
				 */
				FixDayDow(line);
			}
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
			/* copy mailto (can be NULL) */
			line->cl_mailto = xstrdup(mailTo);
#endif
			line->cl_shell = xstrdup(shell);
			/* copy command */
			line->cl_cmd = xstrdup(tokens[5]);
			pline = &line->cl_next;
//bb_error_msg("M[%s]F[%s][%s][%s][%s][%s][%s]", mailTo, tokens[0], tokens[1], tokens[2], tokens[3], tokens[4], tokens[5]);
		}
		*pline = NULL;

		file->cf_next = G.cron_files;
		G.cron_files = file;
	}
	config_close(parser);
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
	free(mailTo);
#endif
	free(shell);
}

static void process_cron_update_file(void)
{
	FILE *fi;
	char buf[256];

	fi = fopen_for_read(CRONUPDATE);
	if (fi != NULL) {
		unlink(CRONUPDATE);
		while (fgets(buf, sizeof(buf), fi) != NULL) {
			/* use first word only */
			skip_non_whitespace(buf)[0] = '\0';
			load_crontab(buf);
		}
		fclose(fi);
	}
}

static void rescan_crontab_dir(void)
{
	CronFile *file;

	/* Delete all files until we only have ones with running jobs (or none) */
 again:
	for (file = G.cron_files; file; file = file->cf_next) {
		if (!file->cf_deleted) {
			delete_cronfile(file->cf_username);
			goto again;
		}
	}

	/* Remove cron update file */
	unlink(CRONUPDATE);
	/* Re-chdir, in case directory was renamed & deleted */
	xchdir(G.crontab_dir_name);

	/* Scan directory and add associated users */
	{
		DIR *dir = opendir(".");
		struct dirent *den;

		/* xopendir exists, but "can't open '.'" is not informative */
		if (!dir)
			bb_error_msg_and_die("can't open '%s'", G.crontab_dir_name);
		while ((den = readdir(dir)) != NULL) {
			if (strchr(den->d_name, '.') != NULL) {
				continue;
			}
			load_crontab(den->d_name);
		}
		closedir(dir);
	}
}

#if SETENV_LEAKS
/* We set environment *before* vfork (because we want to use vfork),
 * so we cannot use setenv() - repeated calls to setenv() may leak memory!
 * Using putenv(), and freeing memory after unsetenv() won't leak */
static void safe_setenv(char **pvar_val, const char *var, const char *val)
{
	char *var_val = *pvar_val;

	if (var_val) {
		bb_unsetenv_and_free(var_val);
	}
	*pvar_val = xasprintf("%s=%s", var, val);
	putenv(*pvar_val);
}
#endif

static void set_env_vars(struct passwd *pas, const char *shell)
{
	/* POSIX requires crond to set up at least HOME, LOGNAME, PATH, SHELL.
	 * We assume crond inherited suitable PATH.
	 */
#if SETENV_LEAKS
	safe_setenv(&G.env_var_logname, "LOGNAME", pas->pw_name);
	safe_setenv(&G.env_var_user, "USER", pas->pw_name);
	safe_setenv(&G.env_var_home, "HOME", pas->pw_dir);
	safe_setenv(&G.env_var_shell, "SHELL", shell);
#else
	xsetenv("LOGNAME", pas->pw_name);
	xsetenv("USER", pas->pw_name);
	xsetenv("HOME", pas->pw_dir);
	xsetenv("SHELL", shell);
#endif
}

static void change_user(struct passwd *pas)
{
	/* careful: we're after vfork! */
	change_identity(pas); /* - initgroups, setgid, setuid */
	if (chdir(pas->pw_dir) < 0) {
		bb_error_msg("can't change directory to '%s'", pas->pw_dir);
		xchdir(CRON_DIR);
	}
}

// TODO: sendmail should be _run-time_ option, not compile-time!
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL

static pid_t
fork_job(const char *user, int mailFd, CronLine *line, bool run_sendmail)
{
	struct passwd *pas;
	const char *shell, *prog;
	smallint sv_logmode;
	pid_t pid;

	/* prepare things before vfork */
	pas = getpwnam(user);
	if (!pas) {
		bb_error_msg("can't get uid for %s", user);
		goto err;
	}

	shell = line->cl_shell ? line->cl_shell : G.default_shell;
	prog = run_sendmail ? SENDMAIL : shell;

	set_env_vars(pas, shell);

	sv_logmode = logmode;
	pid = vfork();
	if (pid == 0) {
		/* CHILD */
		/* initgroups, setgid, setuid, and chdir to home or CRON_DIR */
		change_user(pas);
		log5("child running %s", prog);
		if (mailFd >= 0) {
			xmove_fd(mailFd, run_sendmail ? 0 : 1);
			dup2(1, 2);
		}
		/* crond 3.0pl1-100 puts tasks in separate process groups */
		bb_setpgrp();
		if (!run_sendmail)
			execlp(prog, prog, "-c", line->cl_cmd, (char *) NULL);
		else
			execlp(prog, prog, SENDMAIL_ARGS, (char *) NULL);
		/*
		 * I want this error message on stderr too,
		 * even if other messages go only to syslog:
		 */
		logmode |= LOGMODE_STDIO;
		bb_error_msg_and_die("can't execute '%s' for user %s", prog, user);
	}
	logmode = sv_logmode;

	if (pid < 0) {
		bb_simple_perror_msg("vfork");
 err:
		pid = 0;
	} /* else: PARENT, FORK SUCCESS */

	/*
	 * Close the mail file descriptor.. we can't just leave it open in
	 * a structure, closing it later, because we might run out of descriptors
	 */
	if (mailFd >= 0) {
		close(mailFd);
	}
	return pid;
}

static pid_t start_one_job(const char *user, CronLine *line)
{
	char mailFile[128];
	int mailFd = -1;

	line->cl_pid = 0;
	line->cl_empty_mail_size = 0;

	if (line->cl_mailto) {
		/* Open mail file (owner is root so nobody can screw with it) */
		snprintf(mailFile, sizeof(mailFile), "%s/cron.%s.%d", CRON_DIR, user, getpid());
		mailFd = open(mailFile, O_CREAT | O_TRUNC | O_WRONLY | O_EXCL | O_APPEND, 0600);

		if (mailFd >= 0) {
			fdprintf(mailFd, "To: %s\nSubject: cron: %s\n\n", line->cl_mailto,
				line->cl_cmd);
			line->cl_empty_mail_size = lseek(mailFd, 0, SEEK_CUR);
		} else {
			bb_error_msg("can't create mail file %s for user %s, "
					"discarding output", mailFile, user);
		}
	}

	line->cl_pid = fork_job(user, mailFd, line, /*sendmail?*/ 0);
	if (mailFd >= 0) {
		if (line->cl_pid <= 0) {
			unlink(mailFile);
		} else {
			/* rename mail-file based on pid of process */
			char *mailFile2 = xasprintf("%s/cron.%s.%d", CRON_DIR, user, (int)line->cl_pid);
			rename(mailFile, mailFile2); // TODO: xrename?
			free(mailFile2);
		}
	}

	return line->cl_pid;
}

/*
 * process_finished_job - called when job terminates and when mail terminates
 */
static void process_finished_job(const char *user, CronLine *line)
{
	pid_t pid;
	int mailFd;
	char mailFile[128];
	struct stat sbuf;

	pid = line->cl_pid;
	line->cl_pid = 0;
	if (pid <= 0) {
		/* No job */
		return;
	}
	if (line->cl_empty_mail_size <= 0) {
		/* End of job and no mail file, or end of sendmail job */
		return;
	}

	/*
	 * End of primary job - check for mail file.
	 * If size has changed and the file is still valid, we send it.
	 */
	snprintf(mailFile, sizeof(mailFile), "%s/cron.%s.%d", CRON_DIR, user, (int)pid);
	mailFd = open(mailFile, O_RDONLY);
	unlink(mailFile);
	if (mailFd < 0) {
		return;
	}

	if (fstat(mailFd, &sbuf) < 0
	 || sbuf.st_uid != DAEMON_UID
	 || sbuf.st_nlink != 0
	 || sbuf.st_size == line->cl_empty_mail_size
	 || !S_ISREG(sbuf.st_mode)
	) {
		close(mailFd);
		return;
	}
	line->cl_empty_mail_size = 0;
	/* if (line->cl_mailto) - always true if cl_empty_mail_size was nonzero */
		line->cl_pid = fork_job(user, mailFd, line, /*sendmail?*/ 1);
}

#else /* !ENABLE_FEATURE_CROND_CALL_SENDMAIL */

static pid_t start_one_job(const char *user, CronLine *line)
{
	const char *shell;
	struct passwd *pas;
	pid_t pid;

	pas = getpwnam(user);
	if (!pas) {
		bb_error_msg("can't get uid for %s", user);
		goto err;
	}

	/* Prepare things before vfork */
	shell = line->cl_shell ? line->cl_shell : G.default_shell;
	set_env_vars(pas, shell);

	/* Fork as the user in question and run program */
	pid = vfork();
	if (pid == 0) {
		/* CHILD */
		/* initgroups, setgid, setuid, and chdir to home or CRON_DIR */
		change_user(pas);
		log5("child running %s", shell);
		/* crond 3.0pl1-100 puts tasks in separate process groups */
		bb_setpgrp();
		execl(shell, shell, "-c", line->cl_cmd, (char *) NULL);
		bb_error_msg_and_die("can't execute '%s' for user %s", shell, user);
	}
	if (pid < 0) {
		bb_simple_perror_msg("vfork");
 err:
		pid = 0;
	}
	line->cl_pid = pid;
	return pid;
}

#define process_finished_job(user, line)  ((line)->cl_pid = 0)

#endif /* !ENABLE_FEATURE_CROND_CALL_SENDMAIL */

/*
 * Determine which jobs need to be run.  Under normal conditions, the
 * period is about a minute (one scan).  Worst case it will be one
 * hour (60 scans).
 */
static void flag_starting_jobs(time_t t1, time_t t2)
{
	time_t t;

	/* Find jobs > t1 and <= t2 */

	for (t = t1 - t1 % 60; t <= t2; t += 60) {
		struct tm *ptm;
		CronFile *file;
		CronLine *line;

		if (t <= t1)
			continue;

		ptm = localtime(&t);
		for (file = G.cron_files; file; file = file->cf_next) {
			log5("file %s:", file->cf_username);
			if (file->cf_deleted)
				continue;
			for (line = file->cf_lines; line; line = line->cl_next) {
				log5(" line %s", line->cl_cmd);
				if (line->cl_Mins[ptm->tm_min]
				 && line->cl_Hrs[ptm->tm_hour]
				 && (line->cl_Days[ptm->tm_mday] || line->cl_Dow[ptm->tm_wday])
				 && line->cl_Mons[ptm->tm_mon]
				) {
					log5(" job: %d %s",
							(int)line->cl_pid, line->cl_cmd);
					if (line->cl_pid > 0) {
						log8("user %s: process already running: %s",
							file->cf_username, line->cl_cmd);
					} else if (line->cl_pid == 0) {
						line->cl_pid = START_ME_NORMAL;
						file->cf_wants_starting = 1;
					}
				}
			}
		}
	}
}

#if ENABLE_FEATURE_CROND_SPECIAL_TIMES
static int touch_reboot_file(void)
{
	int fd = open(CRON_REBOOT, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC, 0000);
	if (fd >= 0) {
		close(fd);
		return 1;
	}
	/* File (presumably) exists - this is not the first run after reboot */
	return 0;
}
#endif

static void start_jobs(int wants_start)
{
	CronFile *file;
	CronLine *line;

	for (file = G.cron_files; file; file = file->cf_next) {
		if (!file->cf_wants_starting)
			continue;

		file->cf_wants_starting = 0;
		for (line = file->cf_lines; line; line = line->cl_next) {
			pid_t pid;
			if (line->cl_pid != wants_start)
				continue;

			pid = start_one_job(file->cf_username, line);
			log8("USER %s pid %3d cmd %s",
				file->cf_username, (int)pid, line->cl_cmd);
			if (pid < 0) {
				file->cf_wants_starting = 1;
			}
			if (pid > 0) {
				file->cf_has_running = 1;
			}
		}
	}
}

/*
 * Check for job completion, return number of jobs still running after
 * all done.
 */
static int check_completions(void)
{
	CronFile *file;
	CronLine *line;
	int num_still_running = 0;

	for (file = G.cron_files; file; file = file->cf_next) {
		if (!file->cf_has_running)
			continue;

		file->cf_has_running = 0;
		for (line = file->cf_lines; line; line = line->cl_next) {
			int r;

			if (line->cl_pid <= 0)
				continue;

			r = waitpid(line->cl_pid, NULL, WNOHANG);
			if (r < 0 || r == line->cl_pid) {
				process_finished_job(file->cf_username, line);
				if (line->cl_pid == 0) {
					/* sendmail was not started for it */
					continue;
				}
				/* else: sendmail was started, job is still running, fall thru */
			}
			/* else: r == 0: "process is still running" */
			file->cf_has_running = 1;
		}
//FIXME: if !file->cf_has_running && file->deleted: delete it!
//otherwise deleted entries will stay forever, right?
		num_still_running += file->cf_has_running;
	}
	return num_still_running;
}

static void reopen_logfile_to_stderr(void)
{
	if (G.log_filename) {
		int logfd = open_or_warn(G.log_filename, O_WRONLY | O_CREAT | O_APPEND);
		if (logfd >= 0)
			xmove_fd(logfd, STDERR_FILENO);
	}
}

int crond_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int crond_main(int argc UNUSED_PARAM, char **argv)
{
	time_t t2;
	unsigned rescan;
	unsigned sleep_time;
	unsigned opts;

	INIT_G();

	opts = getopt32(argv, "^"
			"l:L:fbSc:" IF_FEATURE_CROND_D("d:")
			"\0"
			/* "-b after -f is ignored", and so on for every pair a-b */
			"f-b:b-f:S-L:L-S" IF_FEATURE_CROND_D(":d-l")
			/* -l and -d have numeric param */
			":l+" IF_FEATURE_CROND_D(":d+")
			,
			&G.log_level, &G.log_filename, &G.crontab_dir_name
			IF_FEATURE_CROND_D(,&G.log_level)
	);
	/* both -d N and -l N set the same variable: G.log_level */

	if (!(opts & OPT_f)) {
		/* close stdin, stdout, stderr.
		 * close unused descriptors - don't need them. */
		bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
	}

	if (!(opts & OPT_d) && G.log_filename == NULL) {
		/* logging to syslog */
		openlog(applet_name, LOG_CONS | LOG_PID, LOG_CRON);
		logmode = LOGMODE_SYSLOG;
	}

	//signal(SIGHUP, SIG_IGN); /* ? original crond dies on HUP... */

	reopen_logfile_to_stderr();
	xchdir(G.crontab_dir_name);
	/* $SHELL, or current UID's shell, or DEFAULT_SHELL */
	/* Useful on Android where DEFAULT_SHELL /bin/sh may not exist */
	G.default_shell = xstrdup(get_shell_name());

	log8("crond (busybox "BB_VER") started, log level %d", G.log_level);
	rescan_crontab_dir();
	write_pidfile_std_path_and_ext("crond");
#if ENABLE_FEATURE_CROND_SPECIAL_TIMES
	if (touch_reboot_file())
		start_jobs(START_ME_REBOOT); /* start @reboot entries, if any */
#endif

	/* Main loop */
	t2 = time(NULL);
	rescan = 60;
	sleep_time = 60;
	for (;;) {
		struct stat sbuf;
		time_t t1;
		long dt;

		/* Synchronize to 1 minute, minimum 1 second */
		t1 = t2;
		sleep(sleep_time - (time(NULL) % sleep_time));
		t2 = time(NULL);
		dt = (long)t2 - (long)t1;

		reopen_logfile_to_stderr();

		/*
		 * The file 'cron.update' is checked to determine new cron
		 * jobs.  The directory is rescanned once an hour to deal
		 * with any screwups.
		 *
		 * Check for time jump.  Disparities over an hour either way
		 * result in resynchronization.  A negative disparity
		 * less than an hour causes us to effectively sleep until we
		 * match the original time (i.e. no re-execution of jobs that
		 * have just been run).  A positive disparity less than
		 * an hour causes intermediate jobs to be run, but only once
		 * in the worst case.
		 *
		 * When running jobs, the inequality used is greater but not
		 * equal to t1, and less then or equal to t2.
		 */
		if (stat(G.crontab_dir_name, &sbuf) != 0)
			sbuf.st_mtime = 0; /* force update (once) if dir was deleted */
		if (G.crontab_dir_mtime != sbuf.st_mtime) {
			G.crontab_dir_mtime = sbuf.st_mtime;
			rescan = 1;
		}
		if (--rescan == 0) {
			rescan = 60;
			rescan_crontab_dir();
		}
		process_cron_update_file();
		log5("wakeup dt=%ld", dt);
		if (dt < -60 * 60 || dt > 60 * 60) {
			bb_info_msg("time disparity of %ld minutes detected", dt / 60);
			/* and we do not run any jobs in this case */
		} else if (dt > 0) {
			/* Usual case: time advances forward, as expected */
			flag_starting_jobs(t1, t2);
			start_jobs(START_ME_NORMAL);
			sleep_time = 60;
			if (check_completions() > 0) {
				/* some jobs are still running */
				sleep_time = 10;
			}
		}
		/* else: time jumped back, do not run any jobs */
	} /* for (;;) */

	return 0; /* not reached */
}