regexec获取c中xml标记的值

Question

I'm trying to get the value of xml tags in c programming by regexec and i cannot use xml parser.

Below is my sample code, can someone help in getting the expected output.

char value[500];
regex_t regexp_data;    
regmatch_t matched_data[10];
char pattern_str[] = "<CODE[ \t]*^*>[ \t]*\\(.*\\)[ \t]*<\\/CODE[ \t]*>";
char msg_str[] = "<ROOT><INFO><CODE>5001</CODE><MSG>msg one</MSG></INFO> <INFO><CODE>5002</CODE><MSG>msg two</MSG></INFO></ROOT>";

if ((regcomp(&regexp_data, pattern_str, REG_NEWLINE) == 0) &&
  (regexec(&regexp_data, msg_str, 10, matched_data, 0) == 0))
{
   int i;
   for (i=0; i < 10; ++i)
   {
     memset(value, '\0', sizeof(value));
     memcpy(value, &msg_str[matched_data[i].rm_so], (matched_data[i].rm_eo - matched_data[i].rm_so));

     printf ("value [%s]\n", value);
  }

  regfree(&regexp_data);
}

/*----------------------
Outupt
value [<CODE>5001</CODE><MSG>msg one</MSG></INFO><INFO><CODE>5002</CODE>]
value [5001</CODE><MSG>msg one</MSG></INFO><INFO><CODE>5002]
----------------------
Expected Outupt
value [5001]
value [5002]
----------------------*/

Answer 1

Your regular expression is matching from the first instance of <CODE> to the last instance of </CODE> . To help prevent this, you can replace the (.*\\\\) with ([^<]*\\\\) , so your regex is now:

char pattern_str[] = "<CODE[ \\t]*^*>[ \\t]*\\\\([^<]*\\\\)[ \\t]*<\\\\/CODE[ \\t]*>";

Answer 2

Per Wiktor's comment, .* is too greedy, so I updated the regex to "<CODE[ \\t]*>\\\\s*([0-9]*)\\\\s*<\\\\/CODE[ \\t]*>" and passed in the REG_EXTENDED flag to avoid having to escape the parentheses.

As for capturing multiple matches, you want to follow how the gist Wiktor linked captures multiple matches. In order to get every match, you have to call regexec on the string multiple times while advancing a pointer to the source string by the length of the entire match. The first array element in the array of matches is the entire match, while the subsequent elements are the captured groups. Since you only have one captured group, you only need to pass in a size of 2, not 10. Here's the full code I used:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <regex.h>

int main() {
    char value[500];
    regex_t regexp_data;
    regmatch_t matched_data[2];
    char pattern_str[] = "<CODE[ \t]*>\\s*([0-9]*)\\s*<\\/CODE[ \t]*>";
    char msg_str[] = "<ROOT><INFO><CODE>5001</CODE><MSG>msg one</MSG></INFO><INFO><CODE>5002</CODE><MSG>msg two</MSG></INFO></ROOT>";
    char *cursor = msg_str;

    if (regcomp(&regexp_data, pattern_str, REG_EXTENDED | REG_NEWLINE) != 0) {
        printf("Couldn't compile.\n");
        return 1;
    } 

    while (regexec(&regexp_data, cursor, 2, matched_data, 0) != REG_NOMATCH) {
        memset(value, '\0', sizeof(value));
        memcpy(value, cursor + matched_data[1].rm_so, (matched_data[1].rm_eo - matched_data[1].rm_so));
        printf("value [%s]\n", value);
        cursor += matched_data[0].rm_eo;
    }

    regfree(&regexp_data);
}