/* gidsh.c

   Execute with setgid a Perl or shell script from /home/classes/csXYZ/bin.
   If the filename is NAME, then the Perl script NAME.pl or the shell script
   NAME.sh is executed.

   Hack:  If neither NAME.pl nor NAME.sh exists in /home/classes/csXYZ/bin,
     then execute /home/classes/csXYZ/.bin/NAME.xx.                           */

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include <unistd.h>
#include <grp.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>

#define  MEMORY_LIMIT   8000000000              /* Limit on memory usage */

main (int argc, char *argv[])
{
    char *classes  = "/home/classes";
    char *prefix[] = {"bin", "bin", ".bin"};
    char *suffix[] = {".pl", ".sh", ".xx" };
    int nPrefix    = sizeof(suffix) / sizeof(suffix[0]);

    struct group *group;
    char *base, *csXYZ, *name;
    struct rlimit rlim;
    int i;

    if ((base = rindex(argv[0],'/')))           /* Get base name of file     */
	base++;
    else
	base = argv[0];

    if (! (group = getgrgid (getegid()))) {     /* Get effective group name  */
	perror ("getgrgid failed");
	exit (EXIT_FAILURE);
    }
    csXYZ = strdup (group->gr_name);            /* Suppress TA/UCG suffix    */
    if (strstr (csXYZ, "ta"))
	*strstr (csXYZ, "ta") = 0;
    else if (strstr (csXYZ, "ucg"))
	*strstr (csXYZ, "ucg") = 0;
    else {
	fprintf (stderr, "invalid group: %s\n", csXYZ);
	exit (EXIT_FAILURE);
    }

    if (getrlimit (RLIMIT_AS, &rlim) < 0) {     /* Get limits on memory      */
	perror ("getrlimit failed");
	exit (EXIT_FAILURE);
    }

        if (rlim.rlim_max > MEMORY_LIMIT) {         // Get limits on memory      
	rlim.rlim_max = MEMORY_LIMIT;
	rlim.rlim_cur = MEMORY_LIMIT;
	if (setrlimit (RLIMIT_AS, &rlim) < 0) {
	    perror ("setrlimit failed");
	    exit (EXIT_FAILURE);
	}
	
    }


    for (i = 0;  i < nPrefix;  i++) {
	name = malloc (strlen(classes)
		     + strlen(csXYZ)
		     + strlen(prefix[i])
		     + strlen(base)
		     + strlen(suffix[i])
		     + 4);                      /* Three slashed plus a null */
	sprintf (name,"%s/%s/%s/%s%s",
		 classes, csXYZ, prefix[i], base, suffix[i]);
	execv (name, argv);
    }

    fprintf (stderr, "%s: exec failed\n", base);
    return(-1);
}