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
  20 #include <sys/klog.h>
  21 #include "libbb.h"
  22
  23 int dmesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  24 int dmesg_main(int argc UNUSED_PARAM, char **argv)
  25 {
  26         int len, level;
  27         char *buf;
  28         unsigned opts;
  29         enum {
  30                 OPT_c = 1 << 0,
  31                 OPT_s = 1 << 1,
  32                 OPT_n = 1 << 2
  33         };
  34
  35         opt_complementary = "s+:n+"; /* numeric */
  36         opts = getopt32(argv, "cs:n:", &len, &level);
  37         if (opts & OPT_n) {
  38                 if (klogctl(8, NULL, (long) level))
  39                         bb_perror_msg_and_die("klogctl");
  40                 return EXIT_SUCCESS;
  41         }
  42
  43         if (!(opts & OPT_s))
  44                 len = klogctl(10, NULL, 0); /* read ring buffer size */
  45         if (len < 16*1024)
  46                 len = 16*1024;
  47         if (len > 16*1024*1024)
  48                 len = 16*1024*1024;
  49
  50         buf = xmalloc(len);
  51         len = klogctl(3 + (opts & OPT_c), buf, len); /* read ring buffer */
  52         if (len < 0)
  53                 bb_perror_msg_and_die("klogctl");
  54         if (len == 0)
  55                 return EXIT_SUCCESS;
  56
  57
  58         if (ENABLE_FEATURE_DMESG_PRETTY) {
  59                 int last = '\n';
  60                 int in = 0;
  61
  62                 /* Skip <[0-9]+> at the start of lines */
  63                 while (1) {
  64                         if (last == '\n' && buf[in] == '<') {
  65                                 while (buf[in++] != '>' && in < len)
  66                                         ;
  67                         } else {
  68                                 last = buf[in++];
  69                                 putchar(last);
  70                         }
  71                         if (in >= len)
  72                                 break;
  73                 }
  74                 /* Make sure we end with a newline */
  75                 if (last != '\n')
  76                         bb_putchar('\n');
  77         } else {
  78                 full_write(STDOUT_FILENO, buf, len);
  79                 if (buf[len-1] != '\n')
  80                         bb_putchar('\n');
  81         }
  82
  83         if (ENABLE_FEATURE_CLEAN_UP) free(buf);
  84
  85         return EXIT_SUCCESS;
  86 }