exit() vs _Exit() in C and C++

• Difficulty Level : Medium
• Last Updated : 08 Jun, 2018

In C, exit() terminates the calling process without executing the rest code which is after the exit() function.

Example:-

// C program to illustrate exit() function.

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

    printf("START");

    exit(0); // The program is terminated here

    // This line is not printed

    printf("End of program");

}

Output:

START

Now the question is that if we have exit() function then why C11 standard introduced _Exit()? Actually exit() function performs some cleaning before termination of the program like connection termination, buffer flushes etc. The _Exit() function in C/C++ gives normal termination of a program without performing any cleanup tasks. For example it does not execute functions registered with atexit.

Syntax:

// Here the exit_code represent the exit status// of the program which can be 0 or non-zero.// The _Exit() function returns nothing.void _Exit(int exit_code);

// C++ program to demonstrate use of _Exit()

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

    int exit_code = 10;

    printf("Termination using _Exit");

    _Exit(exit_code);

}

Output:

Showing difference through programs:

// A C++ program to show difference

// between exit() and _Exit()

#include<bits/stdc++.h>

using namespace std;

void fun(void)

{

   cout << "Exiting";

}

int main()

{

   atexit(fun);

   exit(10);

}

Output

Exiting

If we replace exit with _Exit(), then nothing is printed.

// A C++ program to show difference

// between exit() and _Exit()

#include<bits/stdc++.h>

using namespace std;

void fun(void)

{

   cout << "Exiting";

}

int main()

{

   atexit(fun);

   _Exit(10);

}