CODEWITHSUNDEEP
csubstring
Mr Aleph
Mr Aleph

Reputation: 1895

extracting an unknown substring out of a string

I have a program returning data in the following format:

<CFData 0x1001219c0 [0x7fff7027aee0]>{length = 20, capacity = 20, bytes = 0x8deead13b8ae7057f6a629fdaae5e1200bcb8cf5}

I need to extract 8deead13b8ae7057f6a629fdaae5e1200bcb8cf5 (yes, minus the 0x). I tried using sscanf and passing some regular expressions but I have no clue on that.

Any idea how to do this? Code snippets are appreciated.

Upvotes: 1

Views: 539

Answers (2)

hmjd
hmjd

Reputation: 121971

You could use strstr() to locate "bytes = 0x" in the input string and copy the remainder of the string (from the end of "bytes = 0x") except for the last character:

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

int main()
{
    char* s = "<CFData 0x1001219c0 [0x7fff7027aee0]>{length = 20, "
              "capacity = 20, "
              "bytes = 0x8deead13b8ae7057f6a629fdaae5e1200bcb8cf5}";
    char* value = 0;
    const char* begin = strstr(s, "bytes = 0x");

    if (begin)
    {
        begin += 10; /* Move past "bytes = 0x" */
        value = malloc(strlen(begin)); /* Don't need 1 extra for NULL as not
                                          copy last character from 'begin'. */
        if (value)
        {
            memcpy(value, begin, strlen(begin) - 1);
            *(value + strlen(begin) - 1) = 0;
            printf("%s\n", value);
            free(value);
        }
    }
    return 0;
}

Upvotes: 5

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726539

You can use strtok to do the trick.

int main(int argc, char* argv[]) {
    char s[] = "<CFData 0x1001219c0 [0x7fff7027aee0]>{length = 20, capacity = 20, bytes = 0x8deead13b8ae7057f6a629fdaae5e1200bcb8cf5}";
    const char *tok = "<>[]{}= ,";
    char* t = strtok(s, tok);
    int take_next = false;
    char * res;
    while (t) {
        if (take_next) {
            res = t+2;
            break;
        }
        take_next = !strcmp(t, "bytes");
        t = strtok(NULL, tok);
    }
    printf("%s\n", res);
    return 0;
}

Note that this is only a sample. You should strongly consider rewriting this using strtok_r, because strtok is not re-entrant.

Upvotes: 1

Related Questions