Error Handling in C

Error handling in C is the process of detecting, reporting, and handling errors that occur during program execution.
C does not have built-in exception handling, so errors are handled using return values, error codes, and library functions.

Types of Errors in C

1. Compile-time Errors

2. Run-time Errors

3. Logical Errors

1. Compile-time Errors

Errors detected by the compiler.

Examples:

• Syntax errors

• Missing semicolons

• Undeclared variables

2. Run-time Errors

Errors that occur during program execution.

Examples:

• Division by zero

• File not found

• Invalid memory access

3. Logical Errors

Errors in program logic.

Examples:

• Wrong formula

• Incorrect condition

Error Handling Using return Values

Functions return special values to indicate errors.

if (fp == NULL) {
    printf("File cannot be opened");
}

Using errno Variable

• errno is a global variable set when an error occurs

• Requires errno.h

#include 

perror() Function

Prints a descriptive error message.

perror("Error");

strerror() Function

Returns error message as a string.

strerror(errno);

Example Program

#include 
#include 
#include 

int main() {
    FILE *fp;
    fp = fopen("data.txt", "r");

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

    fclose(fp);
    return 0;
}

Handling File Errors

• Check file pointer for NULL

• Use perror() for error description

Handling Memory Allocation Errors

int *p = malloc(10 * sizeof(int));

if (p == NULL) {
    printf("Memory allocation failed");
}

Summary

• C uses manual error handling

• Errors are checked using return values

• errno, perror(), and strerror() help identify errors

• Proper checks prevent program crashes