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annotate toys/lsb/dmesg.c @ 1575:d26f235323db draft

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Update dmesg, loosely based on a patch from Elliott Hughes. Probe the default buffer size, replace the constants with FLAG_x macros, add -r, replace the byte at a time output with a single xwrite(), more comments.
author Rob Landley <rob@landley.net>
date Tue, 25 Nov 2014 21:45:18 -0600
parents 786841fdb1e0
children
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1 /* dmesg.c - display/control kernel ring buffer.
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2 *
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30a6db5a95c2 Add comments about SUSv3 specs (or lack thereof).
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3 * Copyright 2006, 2007 Rob Landley <rob@landley.net>
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4 *
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5 * http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/dmesg.html
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6
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7 // We care that FLAG_c is 1, so keep c at the end.
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8 USE_DMESG(NEWTOY(dmesg, "rs#<1n#c", TOYFLAG_BIN))
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9
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10 config DMESG
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11 bool "dmesg"
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12 default y
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13 help
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14 usage: dmesg [-n LEVEL] [-s SIZE] | -c
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15
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16 Print or control the kernel ring buffer.
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17
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18 -c Clear the ring buffer after printing
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19 -n Set kernel logging LEVEL (1-9)
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20 -r Raw output (with <level markers>)
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21 -s Show the last SIZE many bytes
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22 */
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23
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7e846e281e38 New build infrastructure to generate FLAG_ macros and TT alias, #define FOR_commandname before #including toys.h to trigger it. Rename DEFINE_GLOBALS() to just GLOBALS() (because I could never remember if it was DECLARE_GLOBALS). Convert existing commands to use new infrastructure, and replace optflag constants with FLAG_ macros where appropriate.
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24 #define FOR_dmesg
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25 #include "toys.h"
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26 #include <sys/klog.h>
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28 GLOBALS(
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29 long level;
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30 long size;
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31 )
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32
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33 void dmesg_main(void)
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34 {
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35 // For -n just tell kernel to which messages to keep.
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36 if (toys.optflags & FLAG_n) {
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37 if (klogctl(8, NULL, TT.level)) perror_exit("klogctl");
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38 } else {
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39 char *data, *to, *from;
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40 int size;
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42 // Figure out how much data we need, and fetch it.
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43 size = TT.size;
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44 if (!size && 1>(size = klogctl(10, 0, 0))) perror_exit("klogctl");;
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45 data = to = from = xmalloc(size+1);
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46 size = klogctl(3 + (toys.optflags & FLAG_c), data, size);
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47 if (size < 0) error_exit("klogctl");
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48 data[size] = 0;
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49
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50 // Filter out level markers.
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51 if (!(toys.optflags & FLAG_r)) while ((from - data) < size) {
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52 if ((from == data || from[-1] == '\n') && *from == '<') {
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53 int i = stridx(from, '>');
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55 if (i>0) from += i+1;
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56 }
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57 *(to++) = *(from++);
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58 } else to = data+size;
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59
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60 // Write result. The odds of somebody requesting a buffer of size 3 and
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61 // getting "<1>" are remote, but don't segfault if they do.
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62 if (to != data) {
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63 xwrite(1, data, to-data);
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64 if (to[-1] != '\n') xputc('\n');
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65 }
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66 if (CFG_TOYBOX_FREE) free(data);
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67 }
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68 }