Error Handling (Checking a Return Value)

This lesson covers error handling in C using return values, so you can write a program prepared for unexpected failures. It's for anyone searching "C error handling usage."

C has no exception mechanism, so the standard way to handle errors is indicating success or failure through a function's return value. It's like insurance — deciding ahead of time what to do "just in case something fails."

The example's divide() function passes the calculation result through a pointer, result, and returns 0 on success or -1 on failure. The caller checks whether it succeeded with if (divide(...) == 0).

A common early mistake is moving forward without checking the return value. Forgetting an error check in C doesn't cause a syntax error, so it needs to be a deliberate habit.

In real projects, this return-value-based error handling is used in nearly every operation that can fail — file operations, memory allocation, and more.

📖 Reference code

#include <stdio.h>

int divide(int a, int b, int *result) {
    if (b == 0) return -1;
    *result = a / b;
    return 0;
}

int main(void) {
    int result;
    if (divide(10, 0, &result) == 0) {
        printf("%d\n", result);
    } else {
        printf("Error: cannot divide by zero\n");
    }
    return 0;
}

✍️ Your code

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🧪 This site can't compile or run C directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).