CODEWITHSUNDEEP
cparsingc-strings
user20137453
user20137453

Reputation:

Parsing string between two sets of characters without regex

Say we have a string that goes like "((the)) weather is usually good ((when)) its ((spring))" How can I parse only the words between '((' and '))' without using regex.

Upvotes: 1

Views: 64

Answers (1)

chqrlie
chqrlie

Reputation: 144951

You can use strstr() defined in <string.h> to search for "((", then search from there for "))" to find the end of the match:

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

char *get_word(const char *s, size_t *pos) {
    const char *p1;  // pointer to the next match
    const char *p2;  // pointer to the match end
    p1 = strstr(s + *pos, "((");
    if (p1 == NULL) {
        *pos += strlen(s + *pos);
        return NULL;
    }
    p1 += 2;
    p2 = strstr(p1, "))");
    if (p2 == NULL) {
        // missing end string
        *pos += strlen(s + *pos);
        return NULL;
    }
    *pos = p2 + 2 - s;
    return strndup(p1, p2 - p1);  // allocate a copy of the match
}

int main() {
    const char *str = "((the)) weather is usually good ((when)) it's ((spring))";
    size_t pos = 0;
    char *p;

    while ((p = get_word(s, &pos)) != NULL) {
        printf("%s\n", p);
        free(p);
    }
    return 0;
}

Upvotes: 1

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