micro-utils/sysutils/dmesg.c

#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/klog.h>
#define BUF_SIZE 8196

int main(int argc, char **argv) {
	unsigned int s_size = 0;
	unsigned int n_level = 0;

	int opt;
	while ((opt = getopt(argc, argv, "s:n:")) != -1) {
		switch (opt) {
			case 's':
				s_size = atoi(optarg);
				break;

			case 'n':
				n_level = atoi(optarg);
				break;

			default:
				printf("dmesg\n\t[-n=L Set console logging level] [-s=S Buffer Size]\n");
				return 0;
		}
	}

	/* Setup */
	if (n_level)
		if (klogctl(8, NULL, (long)n_level) < 0) {
			fprintf(stderr, "dmesg: %s\n", strerror(errno));
			return 1;
		}

	if (!s_size)
		s_size = klogctl(10, NULL, 0);


	/* Get kernel log */
	char *buf = malloc(s_size + 1);
	if (buf == NULL) {
		fprintf(stderr, "dmesg: malloc failed\n");
		return 1;
	}

	int n = klogctl(3, buf, s_size);
	if (n <= 0) {
		free(buf);
		if (n == 0)
			return 0;

		fprintf(stderr, "dmesg: %s\n", strerror(errno));
		return 1;
	}


	/* Print */
	write(STDOUT_FILENO, buf, n);
	putchar('\n');

	free(buf);
	return 0;
}