blob: b7b2c69241894f44741a814450e59793d013a85d
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 | //config:config DMESG |
12 | //config: bool "dmesg" |
13 | //config: default y |
14 | //config: select PLATFORM_LINUX |
15 | //config: help |
16 | //config: dmesg is used to examine or control the kernel ring buffer. When the |
17 | //config: Linux kernel prints messages to the system log, they are stored in |
18 | //config: the kernel ring buffer. You can use dmesg to print the kernel's ring |
19 | //config: buffer, clear the kernel ring buffer, change the size of the kernel |
20 | //config: ring buffer, and change the priority level at which kernel messages |
21 | //config: are also logged to the system console. Enable this option if you |
22 | //config: wish to enable the 'dmesg' utility. |
23 | //config: |
24 | //config:config FEATURE_DMESG_PRETTY |
25 | //config: bool "Pretty dmesg output" |
26 | //config: default y |
27 | //config: depends on DMESG |
28 | //config: help |
29 | //config: If you wish to scrub the syslog level from the output, say 'Y' here. |
30 | //config: The syslog level is a string prefixed to every line with the form |
31 | //config: "<#>". |
32 | //config: |
33 | //config: With this option you will see: |
34 | //config: # dmesg |
35 | //config: Linux version 2.6.17.4 ..... |
36 | //config: BIOS-provided physical RAM map: |
37 | //config: BIOS-e820: 0000000000000000 - 000000000009f000 (usable) |
38 | //config: |
39 | //config: Without this option you will see: |
40 | //config: # dmesg |
41 | //config: <5>Linux version 2.6.17.4 ..... |
42 | //config: <6>BIOS-provided physical RAM map: |
43 | //config: <6> BIOS-e820: 0000000000000000 - 000000000009f000 (usable) |
44 | |
45 | //applet:IF_DMESG(APPLET(dmesg, BB_DIR_BIN, BB_SUID_DROP)) |
46 | |
47 | //kbuild:lib-$(CONFIG_DMESG) += dmesg.o |
48 | |
49 | //usage:#define dmesg_trivial_usage |
50 | //usage: "[-c] [-n LEVEL] [-s SIZE]" |
51 | //usage:#define dmesg_full_usage "\n\n" |
52 | //usage: "Print or control the kernel ring buffer\n" |
53 | //usage: "\n -c Clear ring buffer after printing" |
54 | //usage: "\n -n LEVEL Set console logging level" |
55 | //usage: "\n -s SIZE Buffer size" |
56 | //usage: "\n -r Print raw message buffer" |
57 | |
58 | #include <sys/klog.h> |
59 | #include "libbb.h" |
60 | |
61 | int dmesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
62 | int dmesg_main(int argc UNUSED_PARAM, char **argv) |
63 | { |
64 | int len, level; |
65 | char *buf; |
66 | unsigned opts; |
67 | enum { |
68 | OPT_c = 1 << 0, |
69 | OPT_s = 1 << 1, |
70 | OPT_n = 1 << 2, |
71 | OPT_r = 1 << 3 |
72 | }; |
73 | |
74 | opts = getopt32(argv, "cs:+n:+r", &len, &level); |
75 | if (opts & OPT_n) { |
76 | if (klogctl(8, NULL, (long) level)) |
77 | bb_perror_msg_and_die("klogctl"); |
78 | return EXIT_SUCCESS; |
79 | } |
80 | |
81 | if (!(opts & OPT_s)) |
82 | len = klogctl(10, NULL, 0); /* read ring buffer size */ |
83 | if (len < 16*1024) |
84 | len = 16*1024; |
85 | if (len > 16*1024*1024) |
86 | len = 16*1024*1024; |
87 | |
88 | buf = xmalloc(len); |
89 | len = klogctl(3 + (opts & OPT_c), buf, len); /* read ring buffer */ |
90 | if (len < 0) |
91 | bb_perror_msg_and_die("klogctl"); |
92 | if (len == 0) |
93 | return EXIT_SUCCESS; |
94 | |
95 | |
96 | if (ENABLE_FEATURE_DMESG_PRETTY && !(opts & OPT_r)) { |
97 | int last = '\n'; |
98 | int in = 0; |
99 | |
100 | /* Skip <[0-9]+> at the start of lines */ |
101 | while (1) { |
102 | if (last == '\n' && buf[in] == '<') { |
103 | while (buf[in++] != '>' && in < len) |
104 | ; |
105 | } else { |
106 | last = buf[in++]; |
107 | putchar(last); |
108 | } |
109 | if (in >= len) |
110 | break; |
111 | } |
112 | /* Make sure we end with a newline */ |
113 | if (last != '\n') |
114 | bb_putchar('\n'); |
115 | } else { |
116 | full_write(STDOUT_FILENO, buf, len); |
117 | if (buf[len-1] != '\n') |
118 | bb_putchar('\n'); |
119 | } |
120 | |
121 | if (ENABLE_FEATURE_CLEAN_UP) free(buf); |
122 | |
123 | return EXIT_SUCCESS; |
124 | } |
125 |