rails where regex

Using Regular Expressions in C to Match a String

To use regular expressions in C to match a string, you can use the regex.h library. Here are the steps to follow:

1. Include the regex.h header file in your C program.
2. Declare a regex_t variable to hold the compiled regular expression pattern.
3. Use the regcomp() function to compile the regular expression pattern into a form that can be used for matching.
4. Use the regexec() function to match the regular expression pattern against the target string.
5. Check the return value of regexec() to determine if a match was found.
6. If a match was found, you can access the matched substring using the regmatch_t structure returned by regexec().

Here's an example that demonstrates these steps:

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

int main() {
    regex_t regex;
    int ret;
    char target[] = "hi jack here is james";

    // Compile the regular expression pattern
    ret = regcomp(&regex, "jack.james|james.jack", 0);
    if (ret != 0) {
        printf("Failed to compile regex\n");
        return 1;
    }

    // Match the regular expression against the target string
    ret = regexec(&regex, target, 0, NULL, 0);
    if (ret == 0) {
        printf("Match found\n");
    } else if (ret == REG_NOMATCH) {
        printf("No match found\n");
    } else {
        printf("Error in matching\n");
    }

    // Free the compiled regular expression
    regfree(&regex);

    return 0;
}

In this example, the regular expression pattern "jack.james|james.jack" is compiled and then matched against the target string "hi jack here is james". The pattern matches if the string contains both "jack" and "james" in any order. The program outputs "Match found" if a match is found.

Please note that this example uses a simple regular expression pattern for demonstration purposes. You can modify the pattern to suit your specific needs.

[[SOURCE 3]]