Question

How to check if a string is in a valid format ("XXX-XXX-XXXX") with numbers in C

Answer 1

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

int isValidFormat(const char *s) {
    regex_t regex;
    const char *pattern = "^[0-9]{3}-[0-9]{3}-[0-9]{4}$";

    int result = regcomp(&regex, pattern, REG_EXTENDED);
    if (result) {
        fprintf(stderr, "Could not compile regex\n");
        return 0;
    }

    result = regexec(&regex, s, 0, NULL, 0);
    regfree(&regex);

    if (!result) {
        return 1;
    } else {
        return 0;
    }
}

int main() {
    const char *s;

    s = "771-290-1652";
    if (isValidFormat(s)) {
        printf("Valid\n");
    } else {
        printf("Not Valid\n");
    }

    s = "771-29-162";
    if (isValidFormat(s)) {
        printf("Not Valid\n");
    } else {
        printf("Not Valid\n");
    }

    s = "771-AB1-1620";
    if (isValidFormat(s)) {
        printf("Not Valid\n");
    } else {
        printf("Not Valid\n");
    }

    return 0;
}



/*
run:

Valid
Not Valid
Not Valid

*/

 

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