util-linux/dmesg.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  *
   4  * dmesg - display/control kernel ring buffer.
   5  *
   6  * Copyright 2006 Rob Landley <rob@landley.net>
   7  * Copyright 2006 Bernhard Reutner-Fischer <rep.nop@aon.at>
   8  *
   9  * Licensed under GPLv2, see file LICENSE in this source tree.
  10  */
  11
  12 //usage:#define dmesg_trivial_usage
  13 //usage:       "[-c] [-n LEVEL] [-s SIZE]"
  14 //usage:#define dmesg_full_usage "\n\n"
  15 //usage:       "Print or control the kernel ring buffer\n"
  16 //usage:     "\nOptions:"
  17 //usage:     "\n        -c              Clear ring buffer after printing"
  18 //usage:     "\n        -n LEVEL        Set console logging level"
  19 //usage:     "\n        -s SIZE         Buffer size"
  20
  21 #include <sys/klog.h>
  22 #include "libbb.h"
  23
  24 int dmesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  25 int dmesg_main(int argc UNUSED_PARAM, char **argv)
  26 {
  27         int len, level;
  28         char *buf;
  29         unsigned opts;
  30         enum {
  31                 OPT_c = 1 << 0,
  32                 OPT_s = 1 << 1,
  33                 OPT_n = 1 << 2
  34         };
  35
  36         opt_complementary = "s+:n+"; /* numeric */
  37         opts = getopt32(argv, "cs:n:", &len, &level);
  38         if (opts & OPT_n) {
  39                 if (klogctl(8, NULL, (long) level))
  40                         bb_perror_msg_and_die("klogctl");
  41                 return EXIT_SUCCESS;
  42         }
  43
  44         if (!(opts & OPT_s))
  45                 len = klogctl(10, NULL, 0); /* read ring buffer size */
  46         if (len < 16*1024)
  47                 len = 16*1024;
  48         if (len > 16*1024*1024)
  49                 len = 16*1024*1024;
  50
  51         buf = xmalloc(len);
  52         len = klogctl(3 + (opts & OPT_c), buf, len); /* read ring buffer */
  53         if (len < 0)
  54                 bb_perror_msg_and_die("klogctl");
  55         if (len == 0)
  56                 return EXIT_SUCCESS;
  57
  58
  59         if (ENABLE_FEATURE_DMESG_PRETTY) {
  60                 int last = '\n';
  61                 int in = 0;
  62
  63                 /* Skip <#> at the start of lines */
  64                 while (1) {
  65                         if (last == '\n' && buf[in] == '<') {
  66                                 in += 3;
  67                                 if (in >= len)
  68                                         break;
  69                         }
  70                         last = buf[in];
  71                         putchar(last);
  72                         in++;
  73                         if (in >= len)
  74                                 break;
  75                 }
  76                 /* Make sure we end with a newline */
  77                 if (last != '\n')
  78                         bb_putchar('\n');
  79         } else {
  80                 full_write(STDOUT_FILENO, buf, len);
  81                 if (buf[len-1] != '\n')
  82                         bb_putchar('\n');
  83         }
  84
  85         if (ENABLE_FEATURE_CLEAN_UP) free(buf);
  86
  87         return EXIT_SUCCESS;
  88 }