atexit

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

Program support utilities

Program termination
abort exit quick_exit (C11) _Exit (C99)	atexit at_quick_exit (C11) EXIT_SUCCESSEXIT_FAILURE
Communicating with the environment
system	getenvgetenv_s (C11)
Signals
signal raise sig_atomic_t	SIG_DFLSIG_IGN SIG_ERR
Signal types
SIGABRTSIGFPESIGILLSIGINTSIGSEGVSIGTERM
Non-local jumps
setjmp
longjmp
Types
jmp_buf

Defined in header <stdlib.h>
int atexit( void (*func)(void) );

Registers the function pointed to by func to be called on normal program termination (via exit() or returning from main()). The functions will be called in reverse order they were registered, i.e. the function registered last will be executed first.

The same function may be registered more than once.

atexit is thread-safe: calling the function from several threads does not induce a data race.

The implementation is guaranteed to support the registration of at least 32 functions. The exact limit is implementation-defined.

Parameters

func

-

pointer to a function to be called on normal program termination

Return value

0 if the registration succeeds, nonzero value otherwise.

Example

Run this code

#include <stdlib.h>
#include <stdio.h>

void f1(void)
{
    puts("pushed first");
}

void f2(void)
{
    puts("pushed second");
}

int main(void)
{
    atexit(f1);
    atexit(f2);
}

Output:

pushed second
pushed first

References

• C11 standard (ISO/IEC 9899:2011):

• 7.22.4.2 The atexit function (p: 350)

• C99 standard (ISO/IEC 9899:1999):

• 7.20.4.2 The atexit function (p: 315)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.10.4.2 The atexit function

See also

at_quick_exit (C11)

registers a function to be called on quick_exit invocation (function)