Introduction to Error Handling in C

Sure, here's an introductory tutorial on error handling in C.

---

Introduction

In C language, error handling is a crucial part of programming. Despite our best efforts, errors can occur while running a program. These might be due to logical mistakes in the code, invalid user inputs, or even external system errors. Being able to handle these errors gracefully is a key skill, and in C, we do this using error handling techniques.

Types of Errors in C

There are three types of errors in C:

1. Compile-time Errors: These are syntax errors and typos that prevent the program from compiling.
2. Run-time Errors: These are errors that occur while the program is running, like divide by zero or file not found.
3. Logical Errors: These are bugs in the program's logic that produce incorrect results.

Error Handling Techniques

Return Values

One common method for handling errors in C is to use return values. Functions often return a value to indicate whether they were successful or not. For example, a function might return 0 on success and -1 on an error.

int divide(int a, int b) {
    if (b == 0) {
        printf("Error: Division by zero.\n");
        return -1;
    }
    return a / b;
}

Error Numbers (errno)

The errno variable is set by system calls and some library functions to indicate what went wrong. It's a global variable that holds the error number of the last error to occur. You can also check errno in your program to understand what error occurred.

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

void openFile(char *fileName) {
    FILE *file = fopen(fileName, "r");
    if (file == NULL) {
        printf("Error opening file: %s\n", strerror(errno));
    } else {
        fclose(file);
    }
}

perror() and strerror()

perror() and strerror() are two functions used to print human-readable error messages.

• perror(): This function prints a human-readable error message to the standard error output. It takes a string as an argument and appends a colon and a space, followed by the error message and a newline.
• strerror(): This function returns a pointer to the error message string corresponding to the error number passed as an argument.

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

int main() {
    FILE *file = fopen("non_existent_file.txt", "r");
    if (file == NULL) {
        perror("Error opening file");
        printf("Error opening file: %s\n", strerror(errno));
    } else {
        fclose(file);
    }
    return 0;
}

Conclusion

Error handling is a vital part of programming in C. By checking return values, using the errno variable, and employing error message functions like perror() and strerror(), we can catch and handle errors in our programs effectively.

Mastering error handling can help you write more robust and reliable C programs. It's worth your time to understand this topic deeply and practice using these techniques in your own code.

Happy coding!