Question

How to check if a string contains only digits using RegEx in C

Answer 1

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

int is_digits_only(const char *str) {
    regex_t regex;
    int result;

    // Compile the regex to match only digits
    result = regcomp(&regex, "^[0-9]*$", REG_EXTENDED);
    if (result) {
        fprintf(stderr, "Could not compile regex\n");
        return 0;
    }

    // Execute the regex
    result = regexec(&regex, str, 0, NULL, 0);
    regfree(&regex);

    // Return 1 if the string contains only digits, otherwise 0
    return !result;
}

int main() {
    const char *str = "123456";
    
    if (is_digits_only(str)) {
        printf("The string contains only digits.\n");
    } else {
        printf("The string does not contain only digits.\n");
    }
    
    return 0;
}



/*
run:

The string contains only digits.

*/

 

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