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 <stdio.h>
  20 #include <stdlib.h>
  21
  22 #if __GNU_LIBRARY__ < 5
  23
  24 #ifndef __alpha__
  25 # define __NR_klogctl __NR_syslog
  26 static inline _syscall3(int, klogctl, int, type, char *, b, int, len);
  27 #else                                                   /* __alpha__ */
  28 #define klogctl syslog
  29 #endif
  30
  31 #else
  32 # include <sys/klog.h>
  33 #endif
  34
  35 static const char dmesg_usage[] = "dmesg [-c] [-n LEVEL] [-s SIZE]\n"
  36 #ifndef BB_FEATURE_TRIVIAL_HELP
  37         "\nPrints or controls the kernel ring buffer\n\n"
  38         "Options:\n"
  39         "\t-c\t\tClears the ring buffer's contents after printing\n"
  40         "\t-n LEVEL\tSets console logging level\n"
  41         "\t-s SIZE\t\tUse a buffer of size SIZE\n"
  42 #endif
  43         ;
  44
  45 int dmesg_main(int argc, char **argv)
  46 {
  47         char *buf;
  48         int bufsize = 8196;
  49         int i;
  50         int n;
  51         int level = 0;
  52         int lastc;
  53         int cmd = 3;
  54         int stopDoingThat;
  55
  56         argc--;
  57         argv++;
  58
  59         /* Parse any options */
  60         while (argc && **argv == '-') {
  61                 stopDoingThat = FALSE;
  62                 while (stopDoingThat == FALSE && *++(*argv)) {
  63                         switch (**argv) {
  64                         case 'c':
  65                                 cmd = 4;
  66                                 break;
  67                         case 'n':
  68                                 cmd = 8;
  69                                 if (--argc == 0)
  70                                         goto end;
  71                                 level = atoi(*(++argv));
  72                                 if (--argc > 0)
  73                                         ++argv;
  74                                 stopDoingThat = TRUE;
  75                                 break;
  76                         case 's':
  77                                 if (--argc == 0)
  78                                         goto end;
  79                                 bufsize = atoi(*(++argv));
  80                                 if (--argc > 0)
  81                                         ++argv;
  82                                 stopDoingThat = TRUE;
  83                                 break;
  84                         default:
  85                                 goto end;
  86                         }
  87                 }
  88         }
  89
  90         if (argc > 1) {
  91                 goto end;
  92         }
  93
  94         if (cmd == 8) {
  95                 n = klogctl(cmd, NULL, level);
  96                 if (n < 0) {
  97                         goto klogctl_error;
  98                 }
  99                 exit(TRUE);
 100         }
 101
 102         if (bufsize < 4096)
 103                 bufsize = 4096;
 104         buf = (char *) xmalloc(bufsize);
 105         n = klogctl(cmd, buf, bufsize);
 106         if (n < 0) {
 107                 goto klogctl_error;
 108         }
 109
 110         lastc = '\n';
 111         for (i = 0; i < n; i++) {
 112                 if ((i == 0 || buf[i - 1] == '\n') && buf[i] == '<') {
 113                         i++;
 114                         while (buf[i] >= '0' && buf[i] <= '9')
 115                                 i++;
 116                         if (buf[i] == '>')
 117                                 i++;
 118                 }
 119                 lastc = buf[i];
 120                 putchar(lastc);
 121         }
 122         if (lastc != '\n')
 123                 putchar('\n');
 124         exit(TRUE);
 125   end:
 126         usage(dmesg_usage);
 127         exit(FALSE);
 128   klogctl_error:
 129         perror("klogctl");
 130         return(FALSE);
 131 }