make man page and random usage match

[unix-history] / usr / src / games / random / random.c

/*
* Copyright (c) 1994
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Guy Harris at Network Appliance Corp.
*
* %sccs.include.redist.c%
*/

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1994\n\
       The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)random.c    8.3 (Berkeley) %G%";
#endif /* not lint */

#include <sys/types.h>

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

void usage __P((void));

int
main(argc, argv)
       int argc;
       char *argv[];
{
       extern int optind;
       time_t now;
       double denom;
       int ch, random_exit, selected, unbuffer_output;
       char *ep;

       random_exit = unbuffer_output = 0;
       while ((ch = getopt(argc, argv, "er")) != EOF)
               switch (ch) {
               case 'e':
                       random_exit = 1;
                       break;
               case 'r':
                       unbuffer_output = 1;
                       break;
               default:
               case '?':
                       usage();
                       /* NOTREACHED */
               }

       argc -= optind;
       argv += optind;

       switch (argc) {
       case 0:
               denom = 2;
               break;
       case 1:
               errno = 0;
               denom = strtod(*argv, &ep);
               if (errno == ERANGE)
                       err(1, "%s", *argv);
               if (denom == 0 || *ep != '\0')
                       errx(1, "denominator is not valid.");
               break;
       default:
               usage(); 
               /* NOTREACHED */
       }

       (void)time(&now);
       srandom((u_int)(now + getpid()));

       /* Compute a random exit status between 0 and denom - 1. */
       if (random_exit)
               return ((denom * random()) / LONG_MAX);

       /*
        * Act as a filter, randomly choosing lines of the standard input
        * to write to the standard output.
        */
       if (unbuffer_output)
               setbuf(stdout, NULL);
       
       /*
        * Select whether to print the first line.  (Prime the pump.)
        * We find a random number between 0 and denom - 1 and, if it's
        * 0 (which has a 1 / denom chance of being true), we select the
        * line.
        */
       selected = !((denom * random()) / LONG_MAX);
       while ((ch = getchar()) != EOF) {
               if (selected)
                       (void)putchar(ch);
               if (ch == '\n') {
                       /* End of that line.  See if we got an error. */
                       if (ferror(stdout))
                               err(2, "stdout");

                       /* Now see if the next line is to be printed. */
                       selected = !((denom * random()) / LONG_MAX);
               }
       }
       if (ferror(stdin))
               err(2, "stdin");
       exit (0);
}

void
usage()
{
       (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
       exit(1);
}