72 lines
3.2 KiB
C
72 lines
3.2 KiB
C
 
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/* ascii_logparse - demonstrates ASCII mode doing what it is actually for:
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* parsing structured, line-oriented text with named groups, then reading
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* fields back out by name rather than by remembering a numeric position.
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* This is the ordinary, common case the other examples in this directory
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* deliberately are not (they each isolate one less-common feature
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* instead); it is included so the directory has one example that looks
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* like typical real-world usage: log filtering and field extraction.
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*/
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#include "regexx.h"
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#include <stdio.h>
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#include <string.h>
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static const char *LOG =
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"2024-01-15 10:23:45 INFO [auth] user 'alice' logged in from 10.0.0.5\n"
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"2024-01-15 10:24:02 ERROR [db] connection refused to 10.0.0.9:5432\n"
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"2024-01-15 10:24:03 WARN [auth] repeated login failure for user 'bob'\n"
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"2024-01-15 10:25:11 ERROR [auth] user 'bob' locked out after 5 failures\n"
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"2024-01-15 10:26:00 INFO [db] connection pool resized to 32\n";
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int main(void) {
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const char *pattern =
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"(?P<date>\\d{4}-\\d{2}-\\d{2}) (?P<time>\\d{2}:\\d{2}:\\d{2}) "
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"(?P<level>\\w+)\\s+\\[(?P<component>\\w+)\\] (?P<message>.+)";
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PatternError err; memset(&err, 0, sizeof err);
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Pattern *pat = re_compile(pattern, strlen(pattern), ASCII, &err);
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if (!pat) {
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fprintf(stderr, "compile error: %s\n", err.msg);
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PatternError_free(&err);
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return 1;
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}
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printf("-- every ERROR line, fields read back by name --\n");
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size_t linelen = strlen(LOG);
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size_t start = 0;
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int error_count = 0;
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for (size_t pos = 0; pos <= linelen; pos++) {
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if (pos == linelen || LOG[pos] == '\n') {
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size_t len = pos - start;
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if (len > 0) {
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Input *line = Input_from_buffer((const uint8_t *)(LOG + start), len);
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Match m; memset(&m, 0, sizeof m);
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if (Pattern_fullmatch(pat, line, 0, -1, &m) == 1) {
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const char *level; size_t levellen;
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Match_group(&m, "level", 0, &level, &levellen);
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if (levellen == 5 && strncmp(level, "ERROR", 5) == 0) {
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const char *time, *component, *message;
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size_t timelen, componentlen, messagelen;
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Match_group(&m, "time", 0, &time, &timelen);
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Match_group(&m, "component", 0, &component, &componentlen);
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Match_group(&m, "message", 0, &message, &messagelen);
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printf("[%.*s] %.*s: %.*s\n",
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(int)timelen, time,
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(int)componentlen, component,
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(int)messagelen, message);
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error_count++;
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}
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Match_free(&m);
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}
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Input_free(line);
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}
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start = pos + 1;
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}
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}
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printf("\n%d error line(s) found (Pattern_groupindex_lookup(\"message\") = %d,\n"
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"used internally by name lookup so this program never hardcodes a\n"
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"capturing group's numeric position)\n",
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error_count, Pattern_groupindex_lookup(pat, "message"));
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Pattern_free(pat);
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return 0;
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}
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