/*

rnd.c

Generate random numbers

*/

#define _POSIX_SOURCE

#include <stdarg.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

static char *progname;

static void fatal(char *fmt, ...);

static void usage(void);

int main(int argc, char *argv[])

{

int c, i, count;

unsigned long n, v, high, modulus;

unsigned seed;

char *check;

char *c_arg, *m_arg, *s_arg;

(progname=strrchr(argv[0],'/')) ? progname++ : (progname=argv[0]);

c_arg= m_arg= s_arg= NULL;

while (c= getopt(argc, argv, "?c:m:s:"), c != -1)

{

switch(c)

{

case 'c': c_arg= optarg; break;

case 'm': m_arg= optarg; break;

case 's': s_arg= optarg; break;

default:

fatal("getopt failed: '%c'", c);

}

}

if (optind != argc)

usage();

if (c_arg)

{

count= strtol(c_arg, &check, 0);

if (check[0] != '\0')

fatal("bad count '%s'", c_arg);

}

else

count= 1;

if (m_arg)

{

modulus= strtoul(m_arg, &check, 0);

if (check[0] != '\0' || modulus == 0)

fatal("bad modulus '%s'", m_arg);

n= 0x80000000UL / modulus;

if (n == 0)

fatal("bad modulus %lu (too big)", modulus);

high= n * modulus;

}

else

modulus= high= 0x80000000UL;

if (s_arg)

{

seed= strtol(s_arg, &check, 0);

if (check[0] != '\0')

fatal("bad seed '%s'", s_arg);

srandom(seed);

}

for (i= 0; i<count; i++)

{

do

{

v= random();

} while (v > high);

printf("%lu\n", v % modulus);

}

}

static void fatal(char *fmt, ...)

{

va_list ap;

fprintf(stderr, "%s: ", progname);

va_start(ap, fmt);

vfprintf(stderr, fmt, ap);

va_end(ap);

fprintf(stderr, "\n");

exit(1);

}

static void usage(void)

{

fprintf(stderr, "Usage: rnd [-c <count>] [-m <modulus>] [-s <seed>]\n");

exit(1);

}