¿Qué hace atexit?

What does atexit do?

The atexit() function registers the given function to be called at normal process termination, either via exit(3) or via return from the program’s main(). Functions so registered are called in the reverse order of their registration; no arguments are passed.

atextit is a module in python which contains two functions register() and unregister() . Whenever a program is killed by a signal not handled by Python, when os. exit() is called, or Python fatal internal error is detected, the functions registered via this module are not executed.

The exit handlers are called in reverse order of how they were registered with atexit() . The convention is that when program exits cleanly it returns exit status 0 . This can be done by return 0 from main() or exit(0) from anywhere in your program.

The exit function, declared in , terminates a C++ program. The value supplied as an argument to exit is returned to the operating system as the program’s return code or exit code. By convention, a return code of zero means that the program completed successfully.

Is using exit() the same as using return? No. The exit() function is used to exit your program and return control to the operating system. The return statement is used to return from a function and return control to the calling function.

The atexit module provides a simple interface to register functions to be called when a program closes down normally….The callbacks registered with atexit are not invoked if:

1. the program dies because of a signal.
2. os. _exit() is invoked directly.
3. a Python fatal error is detected (in the interpreter)

Python exit commands: quit(), exit(), sys. exit() and os. _exit()

1. quit() It works only if the site module is imported so it should not be used in production code.
2. exit() exit() is defined in site.py and it works only if the site module is imported so it should be used in the interpreter only.
3. sys.exit([arg])
4. os._exit(n)

The atexit () function registers the given function to be called at normal process termination, either via exit (3) or via return from the program’s main (). Functions so registered are called in the reverse order of their registration; no arguments are passed.

If a function exits via an exception, std::terminate is called. 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. 0​ if the registration succeeds, nonzero value otherwise.

Note that atexit only removes the first occurrence of a function from the list, so if a function was placed in the list multiple times with atexit, it must also be removed from the list multiple times. See also: quit .

The atexit () and on_exit (3) functions register functions on the same list: at normal process termination, the registered functions are invoked in reverse order of their registration by these two functions.