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:     "\n        -c              Clear ring buffer after printing"
  17 //usage:     "\n        -n LEVEL        Set console logging level"
  18 //usage:     "\n        -s SIZE         Buffer size"
  19 //usage:     "\n        -r              Print raw message buffer"
  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                 OPT_r = 1 << 3
  35         };
  36
  37         opt_complementary = "s+:n+"; /* numeric */
  38         opts = getopt32(argv, "cs:n:r", &len, &level);
  39         if (opts & OPT_n) {
  40                 if (klogctl(8, NULL, (long) level))
  41                         bb_perror_msg_and_die("klogctl");
  42                 return EXIT_SUCCESS;
  43         }
  44
  45         if (!(opts & OPT_s))
  46                 len = klogctl(10, NULL, 0); /* read ring buffer size */
  47         if (len < 16*1024)
  48                 len = 16*1024;
  49         if (len > 16*1024*1024)
  50                 len = 16*1024*1024;
  51
  52         buf = xmalloc(len);
  53         len = klogctl(3 + (opts & OPT_c), buf, len); /* read ring buffer */
  54         if (len < 0)
  55                 bb_perror_msg_and_die("klogctl");
  56         if (len == 0)
  57                 return EXIT_SUCCESS;
  58
  59
  60         if (ENABLE_FEATURE_DMESG_PRETTY && !(opts & OPT_r)) {
  61                 int last = '\n';
  62                 int in = 0;
  63
  64                 /* Skip <[0-9]+> at the start of lines */
  65                 while (1) {
  66                         if (last == '\n' && buf[in] == '<') {
  67                                 while (buf[in++] != '>' && in < len)
  68                                         ;
  69                         } else {
  70                                 last = buf[in++];
  71                                 putchar(last);
  72                         }
  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 }