dmesg.c

   1 /* vi: set sw=4 ts=4: */
   2 /* dmesg.c -- Print out the contents of the kernel ring buffer
   3  * Created: Sat Oct  9 16:19:47 1993
   4  * Revised: Thu Oct 28 21:52:17 1993 by faith@cs.unc.edu
   5  * Copyright 1993 Theodore Ts'o (tytso@athena.mit.edu)
   6  * This program comes with ABSOLUTELY NO WARRANTY.
   7  * Modifications by Rick Sladkey (jrs@world.std.com)
   8  * Larger buffersize 3 June 1998 by Nicolai Langfeldt, based on a patch
   9  * by Peeter Joot.  This was also suggested by John Hudson.
  10  * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@misiek.eu.org>
  11  * - added Native Language Support
  12  *
  13  * from util-linux -- adapted for busybox by
  14  * Erik Andersen <andersee@debian.org>. I ripped out Native Language
  15  * Support, replaced getopt, added some gotos for redundant stuff.
  16  */
  17
  18 #include "internal.h"
  19 #include <linux/unistd.h>
  20 #include <stdio.h>
  21 #include <getopt.h>
  22 #include <stdlib.h>
  23
  24 #if __GNU_LIBRARY__ < 5
  25
  26 #ifndef __alpha__
  27 # define __NR_klogctl __NR_syslog
  28 static inline _syscall3(int, klogctl, int, type, char *, b, int, len);
  29 #else                                                   /* __alpha__ */
  30 #define klogctl syslog
  31 #endif
  32
  33 #else
  34 # include <sys/klog.h>
  35 #endif
  36
  37 static const char dmesg_usage[] = "dmesg [-c] [-n LEVEL] [-s SIZE]\n"
  38 #ifndef BB_FEATURE_TRIVIAL_HELP
  39         "\nPrints or controls the kernel ring buffer\n\n"
  40         "Options:\n"
  41         "\t-c\t\tClears the ring buffer's contents after printing\n"
  42         "\t-n LEVEL\tSets console logging level\n"
  43         "\t-s SIZE\t\tUse a buffer of size SIZE\n"
  44 #endif
  45         ;
  46
  47 int dmesg_main(int argc, char **argv)
  48 {
  49         char *buf;
  50         int bufsize = 8196;
  51         int i;
  52         int n;
  53         int level = 0;
  54         int lastc;
  55         int cmd = 3;
  56         int stopDoingThat;
  57
  58         argc--;
  59         argv++;
  60
  61         /* Parse any options */
  62         while (argc && **argv == '-') {
  63                 stopDoingThat = FALSE;
  64                 while (stopDoingThat == FALSE && *++(*argv)) {
  65                         switch (**argv) {
  66                         case 'c':
  67                                 cmd = 4;
  68                                 break;
  69                         case 'n':
  70                                 cmd = 8;
  71                                 if (--argc == 0)
  72                                         goto end;
  73                                 level = atoi(*(++argv));
  74                                 if (--argc > 0)
  75                                         ++argv;
  76                                 stopDoingThat = TRUE;
  77                                 break;
  78                         case 's':
  79                                 if (--argc == 0)
  80                                         goto end;
  81                                 bufsize = atoi(*(++argv));
  82                                 if (--argc > 0)
  83                                         ++argv;
  84                                 stopDoingThat = TRUE;
  85                                 break;
  86                         default:
  87                                 goto end;
  88                         }
  89                 }
  90         }
  91
  92         if (argc > 1) {
  93                 goto end;
  94         }
  95
  96         if (cmd == 8) {
  97                 n = klogctl(cmd, NULL, level);
  98                 if (n < 0) {
  99                         goto klogctl_error;
 100                 }
 101                 exit(TRUE);
 102         }
 103
 104         if (bufsize < 4096)
 105                 bufsize = 4096;
 106         buf = (char *) xmalloc(bufsize);
 107         n = klogctl(cmd, buf, bufsize);
 108         if (n < 0) {
 109                 goto klogctl_error;
 110         }
 111
 112         lastc = '\n';
 113         for (i = 0; i < n; i++) {
 114                 if ((i == 0 || buf[i - 1] == '\n') && buf[i] == '<') {
 115                         i++;
 116                         while (buf[i] >= '0' && buf[i] <= '9')
 117                                 i++;
 118                         if (buf[i] == '>')
 119                                 i++;
 120                 }
 121                 lastc = buf[i];
 122                 putchar(lastc);
 123         }
 124         if (lastc != '\n')
 125                 putchar('\n');
 126         exit(TRUE);
 127   end:
 128         usage(dmesg_usage);
 129         exit(FALSE);
 130   klogctl_error:
 131         perror("klogctl");
 132         exit(FALSE);
 133
 134 }