usr.sbin/cron/cron.c

/* Copyright 1988,1990,1993,1994 by Paul Vixie
 * All rights reserved
 *
 * Distribute freely, except: don't remove my name from the source or
 * documentation (don't take credit for my work), mark your changes (don't
 * get me blamed for your possible bugs), don't alter or remove this
 * notice.  May be sold if buildable source is provided to buyer.  No
 * warrantee of any kind, express or implied, is included with this
 * software; use at your own risk, responsibility for damages (if any) to
 * anyone resulting from the use of this software rests entirely with the
 * user.
 *
 * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
 * I'll try to keep a version up to date.  I can be reached as follows:
 * Paul Vixie          <paul@vix.com>          uunet!decwrl!vixie!paul
 * From Id: cron.c,v 2.11 1994/01/15 20:43:43 vixie Exp
 */

#if !defined(lint) && !defined(LINT)
static char rcsid[] = "$Header: $";
#endif


#define MAIN_PROGRAM


#include "cron.h"
#include <sys/signal.h>
#if SYS_TIME_H
# include <sys/time.h>
#else
# include <time.h>
#endif


static  void    usage __P((void)),
                run_reboot_jobs __P((cron_db *)),
                cron_tick __P((cron_db *)),
                cron_sync __P((void)),
                cron_sleep __P((void)),
#ifdef USE_SIGCHLD
                sigchld_handler __P((int)),
#endif
                sighup_handler __P((int)),
                parse_args __P((int c, char *v[]));


static void
usage() {
        fprintf(stderr, "usage:  %s [-x debugflag[,...]]\n", ProgramName);
        exit(ERROR_EXIT);
}


int
main(argc, argv)
        int     argc;
        char    *argv[];
{
        cron_db database;

        ProgramName = argv[0];

#if defined(BSD)
        setlinebuf(stdout);
        setlinebuf(stderr);
#endif

        parse_args(argc, argv);

#ifdef USE_SIGCHLD
        (void) signal(SIGCHLD, sigchld_handler);
#else
        (void) signal(SIGCLD, SIG_IGN);
#endif
        (void) signal(SIGHUP, sighup_handler);

        acquire_daemonlock(0);
        set_cron_uid();
        set_cron_cwd();

#if defined(POSIX)
        setenv("PATH", _PATH_DEFPATH, 1);
#endif

        /* if there are no debug flags turned on, fork as a daemon should.
         */
# if DEBUGGING
        if (DebugFlags) {
# else
        if (0) {
# endif
                (void) fprintf(stderr, "[%d] cron started\n", getpid());
        } else {
                switch (fork()) {
                case -1:
                        log_it("CRON",getpid(),"DEATH","can't fork");
                        exit(0);
                        break;
                case 0:
                        /* child process */
                        log_it("CRON",getpid(),"STARTUP","fork ok");
                        (void) setsid();
                        break;
                default:
                        /* parent process should just die */
                        _exit(0);
                }
        }

        acquire_daemonlock(0);
        database.head = NULL;
        database.tail = NULL;
        database.mtime = (time_t) 0;
        load_database(&database);
        run_reboot_jobs(&database);
        cron_sync();
        while (TRUE) {
# if DEBUGGING
                if (!(DebugFlags & DTEST))
# endif /*DEBUGGING*/
                        cron_sleep();

                load_database(&database);

                /* do this iteration
                 */
                cron_tick(&database);

                /* sleep 1 minute
                 */
                TargetTime += 60;
        }
}


static void
run_reboot_jobs(db)
        cron_db *db;
{
        register user           *u;
        register entry          *e;

        for (u = db->head;  u != NULL;  u = u->next) {
                for (e = u->crontab;  e != NULL;  e = e->next) {
                        if (e->flags & WHEN_REBOOT) {
                                job_add(e, u);
                        }
                }
        }
        (void) job_runqueue();
}


static void
cron_tick(db)
        cron_db *db;
{
        register struct tm      *tm = localtime(&TargetTime);
        register int            minute, hour, dom, month, dow;
        register user           *u;
        register entry          *e;

        /* make 0-based values out of these so we can use them as indicies
         */
        minute = tm->tm_min -FIRST_MINUTE;
        hour = tm->tm_hour -FIRST_HOUR;
        dom = tm->tm_mday -FIRST_DOM;
        month = tm->tm_mon +1 /* 0..11 -> 1..12 */ -FIRST_MONTH;
        dow = tm->tm_wday -FIRST_DOW;

        Debug(DSCH, ("[%d] tick(%d,%d,%d,%d,%d)\n",
                getpid(), minute, hour, dom, month, dow))

        /* the dom/dow situation is odd.  '* * 1,15 * Sun' will run on the
         * first and fifteenth AND every Sunday;  '* * * * Sun' will run *only*
         * on Sundays;  '* * 1,15 * *' will run *only* the 1st and 15th.  this
         * is why we keep 'e->dow_star' and 'e->dom_star'.  yes, it's bizarre.
         * like many bizarre things, it's the standard.
         */
        for (u = db->head;  u != NULL;  u = u->next) {
                for (e = u->crontab;  e != NULL;  e = e->next) {
                        Debug(DSCH|DEXT, ("user [%s:%d:%d:...] cmd=\"%s\"\n",
                                          env_get("LOGNAME", e->envp),
                                          e->uid, e->gid, e->cmd))
                        if (bit_test(e->minute, minute)
                         && bit_test(e->hour, hour)
                         && bit_test(e->month, month)
                         && ( ((e->flags & DOM_STAR) || (e->flags & DOW_STAR))
                              ? (bit_test(e->dow,dow) && bit_test(e->dom,dom))
                              : (bit_test(e->dow,dow) || bit_test(e->dom,dom))
                            )
                           ) {
                                job_add(e, u);
                        }
                }
        }
}


/* the task here is to figure out how long it's going to be until :00 of the
 * following minute and initialize TargetTime to this value.  TargetTime
 * will subsequently slide 60 seconds at a time, with correction applied
 * implicitly in cron_sleep().  it would be nice to let cron execute in
 * the "current minute" before going to sleep, but by restarting cron you
 * could then get it to execute a given minute's jobs more than once.
 * instead we have the chance of missing a minute's jobs completely, but
 * that's something sysadmin's know to expect what with crashing computers..
 */
static void
cron_sync() {
        register struct tm      *tm;

        TargetTime = time((time_t*)0);
        tm = localtime(&TargetTime);
        TargetTime += (60 - tm->tm_sec);
}


static void
cron_sleep() {
        register int    seconds_to_wait;

        do {
                seconds_to_wait = (int) (TargetTime - time((time_t*)0));
                Debug(DSCH, ("[%d] TargetTime=%ld, sec-to-wait=%d\n",
                        getpid(), TargetTime, seconds_to_wait))

                /* if we intend to sleep, this means that it's finally
                 * time to empty the job queue (execute it).
                 *
                 * if we run any jobs, we'll probably screw up our timing,
                 * so go recompute.
                 *
                 * note that we depend here on the left-to-right nature
                 * of &&, and the short-circuiting.
                 */
        } while (seconds_to_wait > 0 && job_runqueue());

        while (seconds_to_wait > 0) {
                Debug(DSCH, ("[%d] sleeping for %d seconds\n",
                        getpid(), seconds_to_wait))
                seconds_to_wait = (int) sleep((unsigned int) seconds_to_wait);
        }
}


#ifdef USE_SIGCHLD
static void
sigchld_handler(x) {
        WAIT_T          waiter;
        PID_T           pid;

        for (;;) {
#ifdef POSIX
                pid = waitpid(-1, &waiter, WNOHANG);
#else
                pid = wait3(&waiter, WNOHANG, (struct rusage *)0);
#endif
                switch (pid) {
                case -1:
                        Debug(DPROC,
                                ("[%d] sigchld...no children\n", getpid()))
                        return;
                case 0:
                        Debug(DPROC,
                                ("[%d] sigchld...no dead kids\n", getpid()))
                        return;
                default:
                        Debug(DPROC,
                                ("[%d] sigchld...pid #%d died, stat=%d\n",
                                getpid(), pid, WEXITSTATUS(waiter)))
                }
        }
}
#endif /*USE_SIGCHLD*/


static void
sighup_handler(x) {
        log_close();
}


static void
parse_args(argc, argv)
        int     argc;
        char    *argv[];
{
        int     argch;

        while (EOF != (argch = getopt(argc, argv, "x:"))) {
                switch (argch) {
                default:
                        usage();
                case 'x':
                        if (!set_debug_flags(optarg))
                                usage();
                        break;
                }
        }
}