Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!mcsun!hp4nl!star.cs.vu.nl!maart
From: maart@cs.vu.nl (Maarten Litmaath)
Newsgroups: comp.unix.wizards
Subject: Re: Cron - First Saturday of the month
Message-ID: <7286@star.cs.vu.nl>
Date: 10 Aug 90 17:26:39 GMT
References: <19744@orstcs.CS.ORST.EDU> <1990Aug8.185745.16606@iwarp.intel.com> <1990Aug8.214539.1264@watserv1.waterloo.edu> <1990Aug9.001850.19494@iwarp.intel.com> <1990Aug10.040654.17334@watserv1.waterloo.edu> <1990Aug10.063819.5253@iwarp.intel.com>
Sender: news@cs.vu.nl
Reply-To: maart@cs.vu.nl (Maarten Litmaath)
Organization: VU Dept. of Computer Science, Amsterdam, The Netherlands
Lines: 87

The manual (man 5 crontab on SunOS 4.0.3c):

     [...]
     Note: the specification of days may be made  by  two  fields
     (day  of the month and day of the week).  If both are speci-
     fied as a list of elements, both are adhered to.  For  exam-
     ple,

          0 0 1,15 * 1

     would run a command on  the  first  and  fifteenth  of  each
     month,  as well as on every Monday.  To specify days by only
     one field, the other field should be set to *.  For example,

          0 0 * * 1

     would run a command only on Mondays.
     [...]

The code:

	int
	match(cp, loct)
		register char **cp;
		register struct	tm *loct;
	{
		int	cancel_ex = 0;

		*cp = cmp(*cp, loct->tm_min, &cancel_ex);
		*cp = cmp(*cp, loct->tm_hour, &cancel_ex);
		*cp = cmp(*cp, loct->tm_mday, &cancel_ex);
		*cp = cmp(*cp, loct->tm_mon, &cancel_ex);
		*cp = cmp(*cp, loct->tm_wday, &cancel_ex);
		return(!cancel_ex);
	}

	char *
	cmp(p, v, cancel_ex)
	char *p;
	int *cancel_ex;
	{
		register char *cp;

		cp = p;
		switch(*cp++) {

		case EXACT:
			if (*cp++ != v)
				(*cancel_ex)++;
			return(cp);

		case ANY:
			return(cp);

		case LIST:
			while(*cp != LIST)
				if(*cp++ == v) {
					while(*cp++ != LIST)
						;
					return(cp);
				}
			(*cancel_ex)++;
			return(cp+1);

		case RANGE:
			if(cp[0] < cp[1]) {
				if(!(cp[0]<=v && cp[1]>=v))
					(*cancel_ex)++;
			} else if(!(v>=cp[0] || v<=cp[1]))
				(*cancel_ex)++;
			return(cp+2);
		}
		if(cp[-1] != v)
			(*cancel_ex)++;
		return(cp);
	}

The conclusion: the manual and the code contradict each other!
The example

          0 0 1,15 * 1

...will run the job on each monday whose date is either the 1st or the 15th!
It might be too late to fix the manual...  (Grrrr!)
--
   "UNIX was never designed to keep people from doing stupid things, because
    that policy would also keep them from doing clever things."  (Doug Gwyn)