1 /* dmesg.c - display/control kernel ring buffer.
2 *
3 * Copyright 2006, 2007 Rob Landley <rob@landley.net>
4 *
5 * http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/dmesg.html
6
7 // We care that FLAG_c is 1, so keep c at the end.
8 USE_DMESG(NEWTOY(dmesg, "trs#<1n#c[!tr]", TOYFLAG_BIN))
9
10 config DMESG
11 bool "dmesg"
12 default y
13 help
14 usage: dmesg [-c] [-r|-t] [-n LEVEL] [-s SIZE]
15
16 Print or control the kernel ring buffer.
17
18 -c Clear the ring buffer after printing
19 -n Set kernel logging LEVEL (1-9)
20 -r Raw output (with <level markers>)
21 -s Show the last SIZE many bytes
22 -t Don't print kernel's timestamps
23 */
24
25 #define FOR_dmesg
26 #include "toys.h"
27 #include <sys/klog.h>
28
GLOBALS(long level;long size;)29 GLOBALS(
30 long level;
31 long size;
32 )
33
34 void dmesg_main(void)
35 {
36 // For -n just tell kernel to which messages to keep.
37 if (toys.optflags & FLAG_n) {
38 if (klogctl(8, NULL, TT.level)) perror_exit("klogctl");
39 } else {
40 char *data, *to, *from;
41 int size;
42
43 // Figure out how much data we need, and fetch it.
44 size = TT.size;
45 if (!size && 1>(size = klogctl(10, 0, 0))) perror_exit("klogctl");;
46 data = to = from = xmalloc(size+1);
47 size = klogctl(3 + (toys.optflags & FLAG_c), data, size);
48 if (size < 0) perror_exit("klogctl");
49 data[size] = 0;
50
51 // Filter out level markers and optionally time markers
52 if (!(toys.optflags & FLAG_r)) while ((from - data) < size) {
53 if (from == data || from[-1] == '\n') {
54 char *to;
55
56 if (*from == '<' && (to = strchr(from, '>'))) from = ++to;
57 if ((toys.optflags&FLAG_t) && *from == '[' && (to = strchr(from, ']')))
58 from = to+1+(to[1]==' ');
59 }
60 *(to++) = *(from++);
61 } else to = data+size;
62
63 // Write result. The odds of somebody requesting a buffer of size 3 and
64 // getting "<1>" are remote, but don't segfault if they do.
65 if (to != data) {
66 xwrite(1, data, to-data);
67 if (to[-1] != '\n') xputc('\n');
68 }
69 if (CFG_TOYBOX_FREE) free(data);
70 }
71 }
72