Creating Custom Error Messages in C

Creating Custom Error Messages in C

C programming language provides a built-in error handling mechanism that lets you identify and respond to errors during program execution. However, sometimes, the in-built error messages are not sufficient to explain the problem clearly. In such cases, creating custom error messages can provide a more descriptive and user-friendly way to notify about errors.

Basics of Error Handling in C

In C, error handling involves the use of several library functions such as perror(), strerror(), and errno. Here's a brief description of these functions:

1. perror(): This function displays a string you pass to it, followed by a colon and a space, and then a textual representation of the current errno value.

2. strerror(): This function returns a pointer to the textual representation of the current errno value.

3. errno: This is a preprocessor macro that includes a system-related error number.

Creating Custom Error Messages

To create a custom error message in C, you need to use the printf() function along with the strerror() function or errno variable.

Here's an example of using strerror():

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

int main() {
    FILE *filePtr;

    filePtr = fopen("non_existent_file.txt", "r");

    if (filePtr == NULL) {
        printf("Error: %s\n", strerror(errno));
        return 1;
    }

    fclose(filePtr);

    return 0;
}

In this example, if the file does not exist, the fopen() function returns NULL and sets errno to a value that represents the error. The strerror() function then converts this error number into a human-readable string.

You can also create custom error messages using the perror() function. Here's how you can do this:

#include <stdio.h>

int main() {
    FILE *filePtr;

    filePtr = fopen("non_existent_file.txt", "r");

    if (filePtr == NULL) {
        perror("Error");
        return 1;
    }

    fclose(filePtr);

    return 0;
}

In this example, if the file does not exist, the perror() function will print the string "Error" followed by a colon, a space, and then a textual representation of the error.

Conclusion

In this tutorial, you learned how to create custom error messages in C. While the built-in error messages provided by C are useful, creating custom error messages can provide more clarity and help make your program more user-friendly. Always remember to provide clear and concise error messages that help the user understand what went wrong.