Python os.waitpid() Method

1. Syntax of Python os.waitpid() Method
2. Example 1: Use the os.waitpid() Method in Python
3. Example 2: Shorter Syntax of the os.waitpid() Method

Python os.waitpid() method is an efficient way for a process to wait for the completion of one or more of its child processes, as specified by the input parameter. The functionality of this method differs between UNIX and Windows OS.

Syntax of Python os.waitpid() Method

os.waitpid(pid, options)

Parameters

Return

1. On UNIX: The return type of this method is a tuple representing the process ID of the child process and the exit status.
2. On Windows: The return type of this method is a tuple representing the process ID of any process, and the exit status is shifted to the left by 8 bits. It is shifted to the left so that cross-platform use of the function becomes easier.

Example 1: Use the os.waitpid() Method in Python

import os

pid = os.fork()

if pid > 0:

    process = os.waitpid(pid, 0)

    print("\nParent process:")

    print("Status of child process:", process)

else:

    print("\nChild process:")

    print("The child process ID:", os.getpid())

    print("Hello, World!")

Output:

Child process:
The child process ID: 3186
Hello, World!

Parent process:
Status of child process: (3186, 0)

Note that the os.waitpid() semantics are affected by the parameter options value. In the above code, the integer value of options is 0, which stands for normal operation.

Example 2: Shorter Syntax of the os.waitpid() Method

import os

pid = os.fork()

if pid != 0:

    print("Waiting for the child process to execute: ", os.waitpid(pid, 0))

Output:

Waiting for the child process to execute:  (1505, 0)

On any Windows OS, when the process has exited, the id returned is the same ID, which is reusable.