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 #include <sys/syscall.h>
  27 static inline _syscall3(int, klogctl, int, type, char *, b, int, len);
  28 #else                                                   /* __alpha__ */
  29 #define klogctl syslog
  30 #endif
  31
  32 #else
  33 # include <sys/klog.h>
  34 #endif
  35
  36 static const char dmesg_usage[] = "dmesg [-c] [-n LEVEL] [-s SIZE]\n"
  37 #ifndef BB_FEATURE_TRIVIAL_HELP
  38         "\nPrints or controls the kernel ring buffer\n\n"
  39         "Options:\n"
  40         "\t-c\t\tClears the ring buffer's contents after printing\n"
  41         "\t-n LEVEL\tSets console logging level\n"
  42         "\t-s SIZE\t\tUse a buffer of size SIZE\n"
  43 #endif
  44         ;
  45
  46 int dmesg_main(int argc, char **argv)
  47 {
  48         char *buf;
  49         int bufsize = 8196;
  50         int i;
  51         int n;
  52         int level = 0;
  53         int lastc;
  54         int cmd = 3;
  55         int stopDoingThat;
  56
  57         argc--;
  58         argv++;
  59
  60         /* Parse any options */
  61         while (argc && **argv == '-') {
  62                 stopDoingThat = FALSE;
  63                 while (stopDoingThat == FALSE && *++(*argv)) {
  64                         switch (**argv) {
  65                         case 'c':
  66                                 cmd = 4;
  67                                 break;
  68                         case 'n':
  69                                 cmd = 8;
  70                                 if (--argc == 0)
  71                                         goto end;
  72                                 level = atoi(*(++argv));
  73                                 if (--argc > 0)
  74                                         ++argv;
  75                                 stopDoingThat = TRUE;
  76                                 break;
  77                         case 's':
  78                                 if (--argc == 0)
  79                                         goto end;
  80                                 bufsize = atoi(*(++argv));
  81                                 if (--argc > 0)
  82                                         ++argv;
  83                                 stopDoingThat = TRUE;
  84                                 break;
  85                         default:
  86                                 goto end;
  87                         }
  88                 }
  89         }
  90
  91         if (argc > 1) {
  92                 goto end;
  93         }
  94
  95         if (cmd == 8) {
  96                 n = klogctl(cmd, NULL, level);
  97                 if (n < 0) {
  98                         goto klogctl_error;
  99                 }
 100                 exit(TRUE);
 101         }
 102
 103         if (bufsize < 4096)
 104                 bufsize = 4096;
 105         buf = (char *) xmalloc(bufsize);
 106         n = klogctl(cmd, buf, bufsize);
 107         if (n < 0) {
 108                 goto klogctl_error;
 109         }
 110
 111         lastc = '\n';
 112         for (i = 0; i < n; i++) {
 113                 if ((i == 0 || buf[i - 1] == '\n') && buf[i] == '<') {
 114                         i++;
 115                         while (buf[i] >= '0' && buf[i] <= '9')
 116                                 i++;
 117                         if (buf[i] == '>')
 118                                 i++;
 119                 }
 120                 lastc = buf[i];
 121                 putchar(lastc);
 122         }
 123         if (lastc != '\n')
 124                 putchar('\n');
 125         exit(TRUE);
 126   end:
 127         usage(dmesg_usage);
 128         exit(FALSE);
 129   klogctl_error:
 130         perror("klogctl");
 131         return(FALSE);
 132 }