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- /*
- * Copyright (C) 2016 Etienne Champetier <champetier.etienne@gmail.com>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- */
- #define _GNU_SOURCE
- #include <errno.h>
- #include <linux/random.h>
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <sys/syscall.h>
- #include <unistd.h>
- #define ERROR_EXIT(fmt, ...) do { \
- fprintf(stderr, fmt, ## __VA_ARGS__); \
- return EXIT_FAILURE; \
- } while (0)
- static int usage(char *name)
- {
- fprintf(stderr, "Usage: %s <nb>\n", name);
- fprintf(stderr, " => return <nb> bytes from getrandom()\n");
- return EXIT_FAILURE;
- }
- int main(int argc, char *argv[])
- {
- if (argc != 2)
- return usage(argv[0]);
- if (isatty(STDOUT_FILENO))
- ERROR_EXIT("Not outputting random to a tty\n");
- int nbtot = atoi(argv[1]);
- if (nbtot < 1)
- ERROR_EXIT("Invalid <nb> param (must be > 0)\n");
- char buf[256];
- int len = sizeof(buf);
- while (nbtot > 0) {
- if (nbtot <= sizeof(buf))
- len = nbtot;
- if (syscall(SYS_getrandom, buf, len, 0) == -1)
- ERROR_EXIT("getrandom() failed: %m\n");
- if (write(STDOUT_FILENO, buf, len) != len)
- ERROR_EXIT("write() failed: %m\n");
- nbtot -= sizeof(buf);
- }
- return 0;
- }
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