dmesg.c

/* vi: set sw=4 ts=4: */
/* dmesg.c -- Print out the contents of the kernel ring buffer
 * Created: Sat Oct  9 16:19:47 1993
 * Revised: Thu Oct 28 21:52:17 1993 by faith@cs.unc.edu
 * Copyright 1993 Theodore Ts'o (tytso@athena.mit.edu)
 * This program comes with ABSOLUTELY NO WARRANTY.
 * Modifications by Rick Sladkey (jrs@world.std.com)
 * Larger buffersize 3 June 1998 by Nicolai Langfeldt, based on a patch
 * by Peeter Joot.  This was also suggested by John Hudson.
 * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@misiek.eu.org>
 * - added Native Language Support
 *
 * from util-linux -- adapted for busybox by 
 * Erik Andersen <andersee@debian.org>. I ripped out Native Language 
 * Support, replaced getopt, added some gotos for redundant stuff.
 */

#include "internal.h"
#include <linux/unistd.h>
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>

#if __GNU_LIBRARY__ < 5

#ifndef __alpha__
# define __NR_klogctl __NR_syslog
static inline _syscall3(int, klogctl, int, type, char *, b, int, len);
#else							/* __alpha__ */
#define klogctl syslog
#endif

#else
# include <sys/klog.h>
#endif

static const char dmesg_usage[] = "dmesg [-c] [-n LEVEL] [-s SIZE]\n"
#ifndef BB_FEATURE_TRIVIAL_HELP
	"\nPrints or controls the kernel ring buffer\n\n"
	"Options:\n"
	"\t-c\t\tClears the ring buffer's contents after printing\n"
	"\t-n LEVEL\tSets console logging level\n"
	"\t-s SIZE\t\tUse a buffer of size SIZE\n"
#endif
	;

int dmesg_main(int argc, char **argv)
{
	char *buf;
	int bufsize = 8196;
	int i;
	int n;
	int level = 0;
	int lastc;
	int cmd = 3;
	int stopDoingThat;

	argc--;
	argv++;

	/* Parse any options */
	while (argc && **argv == '-') {
		stopDoingThat = FALSE;
		while (stopDoingThat == FALSE && *++(*argv)) {
			switch (**argv) {
			case 'c':
				cmd = 4;
				break;
			case 'n':
				cmd = 8;
				if (--argc == 0)
					goto end;
				level = atoi(*(++argv));
				if (--argc > 0)
					++argv;
				stopDoingThat = TRUE;
				break;
			case 's':
				if (--argc == 0)
					goto end;
				bufsize = atoi(*(++argv));
				if (--argc > 0)
					++argv;
				stopDoingThat = TRUE;
				break;
			default:
				goto end;
			}
		}
	}

	if (argc > 1) {
		goto end;
	}

	if (cmd == 8) {
		n = klogctl(cmd, NULL, level);
		if (n < 0) {
			goto klogctl_error;
		}
		exit(TRUE);
	}

	if (bufsize < 4096)
		bufsize = 4096;
	buf = (char *) xmalloc(bufsize);
	n = klogctl(cmd, buf, bufsize);
	if (n < 0) {
		goto klogctl_error;
	}

	lastc = '\n';
	for (i = 0; i < n; i++) {
		if ((i == 0 || buf[i - 1] == '\n') && buf[i] == '<') {
			i++;
			while (buf[i] >= '0' && buf[i] <= '9')
				i++;
			if (buf[i] == '>')
				i++;
		}
		lastc = buf[i];
		putchar(lastc);
	}
	if (lastc != '\n')
		putchar('\n');
	exit(TRUE);
  end:
	usage(dmesg_usage);
	exit(FALSE);
  klogctl_error:
	perror("klogctl");
	exit(FALSE);

}