Python | os.waitid() method

OS module in Python provides functions for interacting with the operating system. OS comes under Python’s standard utility modules. This module provides a portable way of using operating system dependent functionality.

os.waitid() method in Python is used by a process to wait for completion of one or more child processes.

Syntax: os.waitid(idtype, id, options)

Parameters:
id: An integer value representing the process id of child to wait on.
idtype: The idtype and id parameter specify which child the method waits for.

Return type: This method returns an object which represents the data contained in siginfo_t structure.

Code #1: Use of os.waitid() method

# Python program to explain os.waitid() method

# importing os module
import os

# Create a child process
# using os.fork() method
pid = os.fork()


# a Non-zero process id (pid)
# indicates the parent process
if pid :

    # Wait for the completion of
    # child process using
    # os.waitid() method

    # Specify idtype
    idtype = os.P_PID

    # Specify id
    id = pid

    # Specify option
    option = os.WEXITED

    status = os.waitid(idtype, id, option)

    print("\nIn parent process-")

    # Print status
    print("Status of child process:")
    print(status)


else :
    print("In Child process-")
    print("Process ID:", os.getpid())
    print("Hello ! Geeks")
    print("Exiting..")

Output:

In Child process-
Process ID: 10309
Hello! Geeks
Exiting..

In parent process-
Status of child process:
posix.waitid_result(si_pid=10309, si_uid=1000, si_signo=17, si_status=0, si_code=1)

Code #2: Use of os.waitid() method

# Python program to explain os.waitid() method

# importing os module
import os

# Create a child process
# using os.fork() method
pid = os.fork()


# a Non-zero process id (pid)
# indicates the parent process
if pid :

    # Create one more child process
    pid2 = os.fork()

    if pid2 :

        # Wait for the completion of
        # any child processes using
        # os.waitid() method

        # Specify idtype
        idtype = os.P_ALL

        # Specify id
        # As idtype is os.P_ALL
                # method will wait for
        # any children and specified id
        # is ignored.
        id = pid

        # Specify option
        option = os.WSTOPPED | os.WEXITED

        status = os.waitid(idtype, id, option)

        print("\nIn parent process-")

        # Print status
        print("Status of completed child process:")
        print(status)

    else :
        print("\nIn Second Child process-")
        print("Process ID:", os.getpid())
        print("Hey ! There  ")
        print("Exiting")


else :
    print("In First Child process-")
    print("Process ID:", os.getpid())
    print("Hello ! Geeks")
    print("Exiting")

Output:

In First Child process-
Process ID: 11524
Hello! Geeks
Exiting

In Second Child process-
Process ID: 11525
Hey! There  
Exiting

In parent process-
Status of completed child process:
posix.waitid_result(si_pid=11524, si_uid=1000, si_signo=17, si_status=0, si_code=1)

References:

• https://docs.python.org/3/library/os.html#os.waitid
• https://linux.die.net/man/3/waitid