Rosetta Code

Random number generator (device): Difference between revisions

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→‎{{header|C}}: The first example now makes fewer assumptions about the host environment (a uint32_t isn't required for this code to work). Additionally, this code compiles as C89 and returns EXIT_FAILURE instead of 1.
Line 27:
It works on systems having /dev/urandom, like [[GNU]]/[[Linux]].
 
<lang c>#include <inttypesstdio.h>
#include <stdiostdlib.h>
#include <stdint.h>
 
#define RANDOM_PATH "/dev/urandom"
int main(int argc, char **argv)
{▼
uint32_t v;
FILE *r = fopen("/dev/urandom", "r");
if (r == NULL)
{▼
perror("/dev/urandom");
return 1;▼
}▼
 
int main(void)
size_t br = fread(&v, sizeof v, 1, r);
▲{
if (br < 1)
unsigned char buf[4];
{
unsigned long v;
fputs("/dev/urandom: Not enough bytes\n", stderr);
FILE *fin;
return 1;
}
 
if ((fin = fopen(RANDOM_PATH, "r")) == NULL) {
printf("%" PRIu32 "\n", v);▼
fprintf(stderr, "%s: unable to open file\n", RANDOM_PATH);
fclose(r);▼
return 0EXIT_FAILURE;
▲ { }
if (fread(buf, 1, sizeof buf, fin) != sizeof buf) {
fprintf(stderr, "%s: not enough bytes (expected %u)\n",
RANDOM_PATH, (unsigned) sizeof buf);
return EXIT_FAILURE;
▲ }
▲ fclose(rfin);
v = buf[0] | buf[1] << 8UL | buf[2] << 16UL | buf[3] << 24UL;
▲ printf("%" PRIu32 "lu\n", v);
▲ return 10;
}</lang>
 
Retrieved from "https://rosettacode.org/wiki/Random_number_generator_(device)"