Program to Pick random values

#include "time.h"
#include "stdio.h"
#include "fcntl.h"
#include "string.h"
#include "stdlib.h"
#include "unistd.h"
#include "getopt.h"
#include "limits.h"
#include "sys/stat.h"
#include "sys/types.h"

#define PACKAGE "raval"
#define VERSION "0.0.1"

/* status epilepticus, print help and exit with `exval' */
void print_help(int exval);
/* picks a radom value withing range low-high*/
int get_rand_val(int low, int high);
/* ! definitely not cryptographic secure ! */
/* value returned seeds the rand() function */
unsigned time_seed(void);

int main(int argc, char *argv[]) {
int opt = 0; /* holds option */
int max = 10; /* upper limit */
int min = 0; /* minimum limit */
int many = 1; /* the number of numbers to pick ... */
char *ptr = NULL; /* separator for number range */

while((opt = getopt(argc, argv, "hvn:r:")) != -1) {
switch(opt) {
case 'h':
print_help(0);
break;
case 'v':
exit(0);
case 'n':
many = atoi(optarg);
break;
case 'r':
if((ptr = strchr(optarg, ':')) == NULL) {
fprintf(stderr, "%s: Error - range `LOW:HIGH'\n\n", PACKAGE);
print_help(1);
} else {
ptr++, max = atoi(ptr);
ptr--, ptr = '\0';
min = atoi(optarg);
if(min >= max || min < 0 || max < 0) {
fprintf(stderr, "%s: Error - range `LOW:HIGH'\n\n", PACKAGE);
print_help(1);
}
}
break;
case '?':
fprintf(stderr, "%s: Error - No such option: `%c'\n\n", PACKAGE, optopt);
print_help(1);
case ':':
fprintf(stderr, "%s: Error - option `%c' needs an argument\n\n", PACKAGE, optopt);
print_help(1);
}
}

/* first seed the random function */
srand((time_seed()));

/* print the random values */
for(; many > 0; many--)
printf("%4d\n", get_rand_val(min, max));

return 0;
}

/* picks a radom value withing range low-high*/
int get_rand_val(int low, int high) {
int k = 0;
double d = 0;

d = (double)rand() / ((double)RAND_MAX + 1);
k = (int)(d * (high - low + 1));

return(low + k);
}

/* ! definitely not cryptographic secure ! */
/* value returned seeds the rand() function */
unsigned time_seed(void) {
int retval = 0;
int fd;

/* just in case open() fails.. */
if(open("/dev/urandom", O_RDONLY) == -1) {
retval = (((int)time(NULL)) & ((1 << 30) - 1)) + getpid();
} else {
read(fd, &retval, 4);
/* positive values only */
retval = abs(retval) + getpid();
close(fd);
}

return retval;
}

void print_help(int exval) {
printf("%s,%s print a random number\n", PACKAGE, VERSION);
printf("Usage: %s OPTION...\n\n", PACKAGE);

printf(" -h print this help and exit\n");
printf(" -v print version and exit\n\n");

printf(" -n INT return `INT' numbers\n");
printf(" -r INT:INT keep the number within range `LOW:HIGH',\n");
printf(" default=(1:10)\n\n");


exit(exval);
}

Related Links :