/* for Unix version 7 */

#include <stdio.h>
#include <utmp.h>

main()
        {
        FILE *utmp;
        if (getuid() != 0)
        {
                printf ("\nNot root, can't shutdown");
                exit(0);
        }

        /* make sure sole user is at console */
        if(strcmp(ttyname(1), "/dev/console"))
                {
                printf("you must shut the system down from the console\n");
                exit(1);
        }
        if((utmp = fopen("/etc/utmp", "r")) == NULL)
                {
                printf("could not open utmp\n");
                exit(1);
        }
        if(! single(utmp)){
                printf("somebody else is still on the system. shutdown aborted.\n");
                execl("/usr/bin/apb", "apb", " I would like to shutdown.", 0);
                exit(1);
        }
        printf("When the single user prompt ('#') is printed, please\n");
        printf("type sync, then halt the cpu\n");
        sync();
        kill(1, 1);
        while(1)
                {
                sync();
                sleep(1);
                }
        }



single(fileid)
        FILE *fileid;
        {
        struct utmp utmp;

        while(!feof(fileid) && !ferror(fileid))
                {
                fread(&utmp, sizeof utmp, 1, fileid);
                if(utmp.ut_name[0] && strcmp(utmp.ut_line, "console"))
                        return(0);
                }
        return(1);
        }