why my PCRE only matches the first result - pcre

Question

I want to match all 'abc' in the input string. But I got the following result when input "first abc, second abc, third abc". I also output the ovector:
src: first abc, second abc, third abc
Matches 1
ovector: 6|9|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|
My code:
#include <stdio.h>
#include <string.h>
#include "pcre.h"
static const char my_pattern[] = "abc";
static pcre* my_pcre = NULL;
static pcre_extra* my_pcre_extra = NULL;
void my_match(const char* src)
{
printf("src: %s\n", src);
int ovector[30]={0};
int ret = pcre_exec(my_pcre, NULL, src, strlen(src), 0, 0, ovector, 30);
if (ret == PCRE_ERROR_NOMATCH){
printf("None match.\n");
}
else{
printf("Matches %d\n",ret);
}
printf("ovector: ");
for(int i=0;i<sizeof(ovector)/sizeof(int);i++){
printf("%d|",ovector[i]);
}
printf("\n");
return;
}
int main()
{
const char* err;
int erroffset;
my_pcre = pcre_compile(my_pattern, PCRE_CASELESS, &err, &erroffset, NULL);
my_pcre_extra = pcre_study(my_pcre, 0, &err);
my_match("first abc, second abc, third abc");
return 0;
}
How can I get all the 'abc's, thanks.

Answer 1

pcre_exec only finds one match at a time. ovector is for substring matches. int ovector[30]={0}; will give you up to 10 matches (the last third (20-29) is not used), the first pair of numbers is for the whole pattern, the next pair is for the first capturing parentheses and so on. E.g. if you change your pattern to:
`static const char my_pattern[] = "(a(b)c)";`
then in your output you should see
Matches 3
ovector: 6|9|6|9|7|8|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|
The function returns the number of captures that matched, in this case three, one for the whole pattern and two subpattern captures. The whole pattern matches at 6-9, the first parentheses match 6-9 too and the second parentheses match 7-8. To get more whole matches (global) you have to use a loop, passing in the offset of the previous match (ovector[1]) each time.
See http://www.pcre.org/pcre.txt and search for How pcre_exec() returns captured substrings