text: /* 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[] ALIGN8 = {
  					/*              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 */
  }
  