NAME

atexit - register a function to run at process termination

SYNOPSIS

#include <stdlib.h>

int atexit(void (*func)(void));


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

The atexit() function shall register the function pointed to by func, to be called without arguments at normal program termination. At normal program termination, all functions registered by the atexit() function shall be called, in the reverse order of their registration, except that a function is called after any previously registered functions that had already been called at the time it was registered. Normal termination occurs either by a call to exit() or a return from main().

At least 32 functions can be registered with atexit().

^[CX] After a successful call to any of the exec functions, any functions previously registered by atexit() shall no longer be registered.

RETURN VALUE

Upon successful completion, atexit() shall return 0; otherwise, it shall return a non-zero value.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

The functions registered by a call to atexit() must return to ensure that all registered functions are called.

The application should call sysconf() to obtain the value of {ATEXIT_MAX}, the number of functions that can be registered. There is no way for an application to tell how many functions have already been registered with atexit().

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

exit() , sysconf() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>

CHANGE HISTORY

First released in Issue 4. Derived from the ANSI C standard.

Issue 6

Extensions beyond the ISO C standard are marked.

The DESCRIPTION is updated for alignment with the ISO/IEC 9899:1999 standard.