Python kill process by pid windows

I'm using Python 2.6. Sometimes there become several instances of a certain process open, and that process causes some problems in itself. I want to be able to programatically detect that there are

I’m using Python 2.6. Sometimes there become several instances of a certain process open, and that process causes some problems in itself. I want to be able to programatically detect that there are multiple instances of that process and to kill them.

For example, maybe in some cases there are 50 instances of make.exe open. I want to be able to tell that there are 20 instances open, and to kill them all. How is this accomplished?

asked Jun 8, 2011 at 12:42

cupof's user avatar

cupofcupof

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1

I would think you could just use taskkill and the Python os.system()

import os
os.system("taskkill /im make.exe")

Note: I would just note you might have to fully qualify the taskkill path. I am using a Linux box so I can’t test…

djvg's user avatar

djvg

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answered Jun 8, 2011 at 12:50

Nix's user avatar

NixNix

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6

Yes,You can do it

import os
os.system("taskkill /f /im  Your_Process_Name.exe")
  1. /f : Specifies that process(es) be forcefully terminated.
  2. /im (ImageName ): Specifies the image name of the process to be
    terminated.
  3. For more info regarding TaskKill

answered Jan 20, 2017 at 2:37

Avinash Jeeva's user avatar

0

You can use the TerminateProcess of the win32 api to kill a process. See the following example : http://code.activestate.com/recipes/347462-terminating-a-subprocess-on-windows/

You need to give it a process handle. If the process is started from your code, the process handle is returned by the CreateProcess or popen.

If the process was started by something else, you need to get this handle you can use EnumProcess or WMI to retrieve it.

answered Jun 8, 2011 at 13:21

luc's user avatar

lucluc

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1

How about this, I tested it with ActiveState Python 2.7:

import sys, traceback, os

def pkill (process_name):
    try:
        killed = os.system('tskill ' + process_name)
    except Exception, e:
        killed = 0
    return killed

call it with:

pkill("program_name")

answered Jul 18, 2014 at 19:26

Giovanni's user avatar

I think the code is like this will work:

import os

def terminate(ProcessName):
    os.system('taskkill /IM "' + ProcessName + '" /F')

terminate('chrome.exe')

answered Jan 12, 2021 at 10:10

Mkrita's user avatar

0

You can kill a process via its process identifier, pid, via the os.kill() function.

In this tutorial you will discover how to kill a process via its pid.

Let’s get started.

Need To Kill a Process by PID

A process is a running instance of a computer program.

Every Python program is executed in a Process, which is a new instance of the Python interpreter. This process has the name MainProcess and has one thread used to execute the program instructions called the MainThread. Both processes and threads are created and managed by the underlying operating system.

Sometimes we may need to create new child processes in our program in order to execute code concurrently.

Python provides the ability to create and manage new processes via the multiprocessing.Process class.

You can learn more about multiprocessing in the tutorial:

  • Multiprocessing in Python: The Complete Guide

In multiprocessing, we may need to kill a process by its process identifier or PID.

This may be for many reasons, such as:

  • The task executed by the process is no longer required.
  • The process has had an error or is out of control.
  • The main program is closing down due to a user request.

How can we kill a process via its pid in Python?

How To Kill a Process via its PID

You can kill a process via its pid with the os.kill() function.

The os.kill function takes two arguments, the process identifier (pid) to kill, and the signal to send to kill the process.

The signal is a constant from the signal module, such as signal.SIGINT or signal.SIGKILL.

For example:

...

# kill a process via pid

os.kill(12345, signal.SIGKILL)

We need to know the pid for the process that is to be killed.

This can be retrieved from the multiprocessing.Process instance for the process via the pid attribute.

For example:

...

# get the pid

pid = process.pid

The multiprocessing.Process instance may be managed by the parent process when the child process is created, or accessed via a module function such as multiprocessing.active_children() or multiprocessing.parent_process().

You can learn more about getting the process pid in the tutorial:

  • How to Get the Process PID in Python

The SIGINT or signal interrupt can be used to terminate the target process, which is equivalent to the user pressing CONTROL-C on the process. Alternately, the SIGKILL or signal kill process can be used to terminate the process forcefully.

The difference between SIGINT and SIGKILL is that it is possible for a process to detect and handle a SIGINT, whereas a SIGKILL cannot be handled.

Now that we know how to kill a process via pid, let’s look at some worked examples.

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Download my FREE PDF cheat sheet

Kill Current Process via PID

It is possible to kill the current process via pid.

This can be achieved by first getting the pid for the current process, then calling os.kill() with the pid and the signal to kill the process, such as SIGKILL.

First, we can get the pid for the current process using the os.getpid(), and report the result.

...

# get the pid of the current process

pid = getpid()

# report a message

print(f‘Running with pid: {pid}’)

Next, we can kill the process using the signal.SIGKILL signal.

...

# attempt to kill the current process

kill(pid, SIGKILL)

Tying this together, the complete example is listed below.

# SuperFastPython.com

# example of killing the current process via pid

from os import kill

from os import getpid

from signal import SIGKILL

# get the pid of the current process

pid = getpid()

# report a message

print(f‘Running with pid: {pid}’)

# attempt to kill the current process

kill(pid, SIGKILL)

# report a message

print(‘Skill running’)

Running the example first gets the pid for the current process, then reports the value.

Note, the pid for the process will differ each time the program is run.

Next, the current process is killed via its pid, e.g, the process kills itself.

Next, let’s look at how we might kill a child process.


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Kill Child Process via PID

We can kill a child process via its pid.

In this example, we will first start a child process that will block for an extended period to keep it occupied. The parent process will then access the pid for the child process and terminate it via the SIGKILL.

First, we can define a function used to run in the new child process.

The task() function below implements this, reporting a message and sleeping for ten seconds.

# function executed in a child process

def task():

    # report a message

    print(‘Child is running…’, flush=True)

    # block for a while

    sleep(10)

Next, the main process will create and configure a new multiprocessing.Process instance to run the function in a new child process. Then the child process is started.

...

# start a child process

child = Process(target=task)

child.start()

The parent process then blocks a moment to allow the child process to start, then reports the pid for the child process via the multiprocessing.Process.pid attribute.

...

# wait a moment

sleep(1)

# report a message

print(f‘Child is running with pid: {child.pid}’)

Next, the child process is killed via its process id and the SIGKILL signal.

...

# attempt to kill the child process

kill(child.pid, SIGKILL)

The parent process then blocks until the child process is completely stopped and then reports the status of the child process.

...

# wait for child to terminate

child.join()

# report status of the child

print(f‘Child process: {child}’)

Tying this together, the complete example is listed below.

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# SuperFastPython.com

# example of killing a child process by pid

from time import sleep

from multiprocessing import Process

from os import kill

from os import getpid

from signal import SIGKILL

# function executed in a child process

def task():

    # report a message

    print(‘Child is running…’, flush=True)

    # block for a while

    sleep(10)

# protect the entry point

if __name__ == ‘__main__’:

    # start a child process

    child = Process(target=task)

    child.start()

    # wait a moment

    sleep(1)

    # report a message

    print(f‘Child is running with pid: {child.pid}’)

    # attempt to kill the child process

    kill(child.pid, SIGKILL)

    # wait for child to terminate

    child.join()

    # report status of the child

    print(f‘Child process: {child}’)

Running the example first configures and starts the child process.

The child process starts, reports a message, then blocks for ten seconds.

The parent process blocks for one second, to allow the child process to start up completely.

The parent process then reports the pid of the child process and kills it via the pid.

The parent process waits for the child process to shutdown completely, then reports the status of the child process.

We can see that the child process is not marked as “stopped” and that its exit code was the negative value of the signal used to terminate it, e.g. -SIGKILL.

Child is running…

Child is running with pid: 21398

Child process: <Process name=’Process-1′ pid=21398 parent=21396 stopped exitcode=-SIGKILL>

Next, let’s look at how we might kill the parent process via pid.

Kill Parent Process via PID

We can kill the parent process via pid.

In this example we can create a child process that will get the pid for the parent process, then kill the parent process via its pid.

First, we can define a function to run in a child process.

# function executed in a child process

def task():

# …

First, the child process will block for a second.

...

# wait a moment

sleep(1)

Next, it will get a multiprocessing.Process instance for the parent process via the multiprocessing.parent_process() module function.

...

# get the parent process

parent = parent_process()

Next, the pid of the parent process is reported.

...

# report a message

print(f‘Parent is running with pid: {parent.pid}’, flush=True)

The parent process can then be killed via its pid.

...

# attempt to kill the parent process

kill(parent.pid, SIGKILL)

The child process then blocks until the parent process has stopped completely, then reports the details of the parent process.

...

# wait for parent to terminate

parent.join()

# report status of the parent

print(f‘Parent process: {parent}’, flush=True)

Tying this together, the complete task() function is listed below.

# function executed in a child process

def task():

    # wait a moment

    sleep(1)

    # get the parent process

    parent = parent_process()

    # report a message

    print(f‘Parent is running with pid: {parent.pid}’, flush=True)

    # attempt to kill the parent process

    kill(parent.pid, SIGKILL)

    # wait for parent to terminate

    parent.join()

    # report status of the parent

    print(f‘Parent process: {parent}’, flush=True)

Next, the main process, the child process is configured and started.

...

# start a child process

child = Process(target=task)

child.start()

The parent process then blocks for ten seconds, waiting to be killed.

...

# wait for a while

sleep(10)

# report a message

print(‘Parent is still running’)

Tying this together, the complete example is listed below.

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# SuperFastPython.com

# example of killing a parent process by pid

from time import sleep

from multiprocessing import parent_process

from multiprocessing import Process

from os import kill

from signal import SIGKILL

# function executed in a child process

def task():

    # wait a moment

    sleep(1)

    # get the parent process

    parent = parent_process()

    # report a message

    print(f‘Parent is running with pid: {parent.pid}’, flush=True)

    # attempt to kill the parent process

    kill(parent.pid, SIGKILL)

    # wait for parent to terminate

    parent.join()

    # report status of the parent

    print(f‘Parent process: {parent}’, flush=True)

# protect the entry point

if __name__ == ‘__main__’:

    # start a child process

    child = Process(target=task)

    child.start()

    # wait for a while

    sleep(10)

    # report a message

    print(‘Parent is still running’)

Running the example first configures and starts a child process.

The parent process then blocks for ten seconds.

The child process blocks for a second, then gets the parent process and reports its pid.

The child process then kills the parent process via its pid.

Next, the child process blocks until the parent process terminates completely, then reports the details of the parent process.

We can see the details of the parent process, which is the main process.

Parent is running with pid: 21421

Parent process: <_ParentProcess name=’MainProcess’ parent=None unknown>

Further Reading

This section provides additional resources that you may find helpful.

Books

  • Python Multiprocessing Jump-Start, Jason Brownlee, 2022 (my book!).
  • Multiprocessing API Interview Questions
  • Multiprocessing Module API Cheat Sheet

I would also recommend specific chapters in the books:

  • Effective Python, Brett Slatkin, 2019.
    • See: Chapter 7: Concurrency and Parallelism
  • High Performance Python, Ian Ozsvald and Micha Gorelick, 2020.
    • See: Chapter 9: The multiprocessing Module
  • Python in a Nutshell, Alex Martelli, et al., 2017.
    • See: Chapter: 14: Threads and Processes

Guides

  • Python Multiprocessing: The Complete Guide

APIs

  • multiprocessing — Process-based parallelism
  • PEP 371 — Addition of the multiprocessing package

    Takeaways

    You now know how to kill a process via its pid.

    Do you have any questions?
    Ask your questions in the comments below and I will do my best to answer.

    Photo by Gene Gallin on Unsplash

    Послать сигнал процессу или группе процессов.

    Синтаксис:

    import os
    
    os.kill(pid, sig)
    os.killpg(pgid, sig)
    

    Параметры:

    • pid — сигнал,
    • sigint процесс,
    • pgidint группа процессов,

    Возвращаемое значение:

    • None

    Вызывает событие аудита os.killpg с аргументами pgid, sig.

    Описание:

    Функция kill() модуля os посылает сигнал sig процессу pid. Константы для конкретных сигналов, доступных на хост-платформе, определяются в модуле signal.

    Функция os.kill() событие аудита os.kill с аргументами pid, sig.

    Функция killpg() посылает сигнал sig в группу процессов pgid. Константы для конкретных сигналов, доступных на хост-платформе, определяются в модуле signal.

    Функция os.killpg() событие аудита os.killpg с аргументами pgid, sig.

    Windows

    : сигналы signal.CTRL_C_EVENT и signal.CTRL_BREAK_EVENT являются специальными сигналами, которые могут отправляться только в консольные процессы, которые совместно используют общее окно консоли, например некоторые подпроцессы. Любое другое значение для sig приведет к безоговорочному завершению процесса API-интерфейсом TerminateProcess, а для кода выхода будет установлено значение sig. Версия os.kill() для Windows дополнительно использует дескрипторы процессов для уничтожения.

    Примеры использования:

    Родитель может отправлять сигналы дочернему процессу, используя функцию os.kill() используя модуль signal. В этом примере используется короткая пауза, чтобы дать дочернему процессу время для настройки обработчика сигнала. Реальное приложение, не будет нуждаться в вызове time.sleep(). В дочернем процессе установим обработчик сигнала и сделаем небольшую паузу, чтобы предоставить родительскому процессу достаточно времени для отправки сигнала.

    import os
    import signal
    import time
    
    def signal_usr1(signum, frame):
        "Обратный вызов вызывается при получении сигнала"
        pid = os.getpid()
        print(f'Получен USR1 в процессе {pid}')
    
    print('Forking...')
    child_pid = os.fork()
    if child_pid:
        print('PARENT: Пауза перед отправкой сигнала ...')
        time.sleep(1)
        print(f'PARENT: передача сигналов {child_pid}')
        os.kill(child_pid, signal.SIGUSR1)
    else:
        print('CHILD: Настройка обработчика сигнала')
        signal.signal(signal.SIGUSR1, signal_usr1)
        print('CHILD: Пауза в ожидании сигнала')
        time.sleep(5)
    
    # $ python3 test_kill.py
    # Forking...
    # PARENT: Пауза перед отправкой сигнала ...
    # CHILD: Настройка обработчика сигнала
    # CHILD: Пауза в ожидании сигнала
    # PARENT: передача сигналов 21168
    # Получен USR1 в процессе 21168
    

    Source code: Lib/os.py


    This module provides a portable way of using operating system dependent
    functionality. If you just want to read or write a file see open(), if
    you want to manipulate paths, see the os.path module, and if you want to
    read all the lines in all the files on the command line see the fileinput
    module. For creating temporary files and directories see the tempfile
    module, and for high-level file and directory handling see the shutil
    module.

    Notes on the availability of these functions:

    • The design of all built-in operating system dependent modules of Python is
      such that as long as the same functionality is available, it uses the same
      interface; for example, the function os.stat(path) returns stat
      information about path in the same format (which happens to have originated
      with the POSIX interface).
    • Extensions peculiar to a particular operating system are also available
      through the os module, but using them is of course a threat to
      portability.
    • All functions accepting path or file names accept both bytes and string
      objects, and result in an object of the same type, if a path or file name is
      returned.
    • An “Availability: Unix” note means that this function is commonly found on
      Unix systems. It does not make any claims about its existence on a specific
      operating system.
    • If not separately noted, all functions that claim “Availability: Unix” are
      supported on Mac OS X, which builds on a Unix core.

    Note

    All functions in this module raise OSError in the case of invalid or
    inaccessible file names and paths, or other arguments that have the correct
    type, but are not accepted by the operating system.

    exception os.error

    An alias for the built-in OSError exception.

    os.name

    The name of the operating system dependent module imported. The following
    names have currently been registered: 'posix', 'nt',
    'java'.

    See also

    sys.platform has a finer granularity. os.uname() gives
    system-dependent version information.

    The platform module provides detailed checks for the
    system’s identity.

    16.1.1. File Names, Command Line Arguments, and Environment Variables¶

    In Python, file names, command line arguments, and environment variables are
    represented using the string type. On some systems, decoding these strings to
    and from bytes is necessary before passing them to the operating system. Python
    uses the file system encoding to perform this conversion (see
    sys.getfilesystemencoding()).

    Changed in version 3.1: On some systems, conversion using the file system encoding may fail. In this
    case, Python uses the surrogateescape encoding error handler, which means that undecodable bytes are replaced by a
    Unicode character U+DCxx on decoding, and these are again translated to the
    original byte on encoding.

    The file system encoding must guarantee to successfully decode all bytes
    below 128. If the file system encoding fails to provide this guarantee, API
    functions may raise UnicodeErrors.

    16.1.2. Process Parameters¶

    These functions and data items provide information and operate on the current
    process and user.

    os.ctermid()

    Return the filename corresponding to the controlling terminal of the process.

    Availability: Unix.

    os.environ

    A mapping object representing the string environment. For example,
    environ['HOME'] is the pathname of your home directory (on some platforms),
    and is equivalent to getenv("HOME") in C.

    This mapping is captured the first time the os module is imported,
    typically during Python startup as part of processing site.py. Changes
    to the environment made after this time are not reflected in os.environ,
    except for changes made by modifying os.environ directly.

    If the platform supports the putenv() function, this mapping may be used
    to modify the environment as well as query the environment. putenv() will
    be called automatically when the mapping is modified.

    On Unix, keys and values use sys.getfilesystemencoding() and
    'surrogateescape' error handler. Use environb if you would like
    to use a different encoding.

    Note

    Calling putenv() directly does not change os.environ, so it’s better
    to modify os.environ.

    Note

    On some platforms, including FreeBSD and Mac OS X, setting environ may
    cause memory leaks. Refer to the system documentation for
    putenv().

    If putenv() is not provided, a modified copy of this mapping may be
    passed to the appropriate process-creation functions to cause child processes
    to use a modified environment.

    If the platform supports the unsetenv() function, you can delete items in
    this mapping to unset environment variables. unsetenv() will be called
    automatically when an item is deleted from os.environ, and when
    one of the pop() or clear() methods is called.

    os.environb

    Bytes version of environ: a mapping object representing the
    environment as byte strings. environ and environb are
    synchronized (modify environb updates environ, and vice
    versa).

    environb is only available if supports_bytes_environ is
    True.

    New in version 3.2.

    os.chdir(path)
    os.fchdir(fd)
    os.getcwd()

    These functions are described in Files and Directories.

    os.fsencode(filename)

    Encode path-like filename to the filesystem
    encoding with 'surrogateescape' error handler, or 'strict' on
    Windows; return bytes unchanged.

    fsdecode() is the reverse function.

    New in version 3.2.

    Changed in version 3.6: Support added to accept objects implementing the os.PathLike
    interface.

    os.fsdecode(filename)

    Decode the path-like filename from the
    filesystem encoding with 'surrogateescape' error handler, or 'strict'
    on Windows; return str unchanged.

    fsencode() is the reverse function.

    New in version 3.2.

    Changed in version 3.6: Support added to accept objects implementing the os.PathLike
    interface.

    os.fspath(path)

    Return the file system representation of the path.

    If str or bytes is passed in, it is returned unchanged.
    Otherwise __fspath__() is called and its value is
    returned as long as it is a str or bytes object.
    In all other cases, TypeError is raised.

    New in version 3.6.

    class os.PathLike

    An abstract base class for objects representing a file system path,
    e.g. pathlib.PurePath.

    New in version 3.6.

    abstractmethod __fspath__()

    Return the file system path representation of the object.

    The method should only return a str or bytes object,
    with the preference being for str.

    os.getenv(key, default=None)

    Return the value of the environment variable key if it exists, or
    default if it doesn’t. key, default and the result are str.

    On Unix, keys and values are decoded with sys.getfilesystemencoding()
    and 'surrogateescape' error handler. Use os.getenvb() if you
    would like to use a different encoding.

    Availability: most flavors of Unix, Windows.

    os.getenvb(key, default=None)

    Return the value of the environment variable key if it exists, or
    default if it doesn’t. key, default and the result are bytes.

    getenvb() is only available if supports_bytes_environ
    is True.

    Availability: most flavors of Unix.

    New in version 3.2.

    os.get_exec_path(env=None)

    Returns the list of directories that will be searched for a named
    executable, similar to a shell, when launching a process.
    env, when specified, should be an environment variable dictionary
    to lookup the PATH in.
    By default, when env is None, environ is used.

    New in version 3.2.

    os.getegid()

    Return the effective group id of the current process. This corresponds to the
    “set id” bit on the file being executed in the current process.

    Availability: Unix.

    os.geteuid()

    Return the current process’s effective user id.

    Availability: Unix.

    os.getgid()

    Return the real group id of the current process.

    Availability: Unix.

    os.getgrouplist(user, group)

    Return list of group ids that user belongs to. If group is not in the
    list, it is included; typically, group is specified as the group ID
    field from the password record for user.

    Availability: Unix.

    New in version 3.3.

    os.getgroups()

    Return list of supplemental group ids associated with the current process.

    Availability: Unix.

    Note

    On Mac OS X, getgroups() behavior differs somewhat from
    other Unix platforms. If the Python interpreter was built with a
    deployment target of 10.5 or earlier, getgroups() returns
    the list of effective group ids associated with the current user process;
    this list is limited to a system-defined number of entries, typically 16,
    and may be modified by calls to setgroups() if suitably privileged.
    If built with a deployment target greater than 10.5,
    getgroups() returns the current group access list for the user
    associated with the effective user id of the process; the group access
    list may change over the lifetime of the process, it is not affected by
    calls to setgroups(), and its length is not limited to 16. The
    deployment target value, MACOSX_DEPLOYMENT_TARGET, can be
    obtained with sysconfig.get_config_var().

    os.getlogin()

    Return the name of the user logged in on the controlling terminal of the
    process. For most purposes, it is more useful to use the environment
    variables LOGNAME or USERNAME to find out who the user
    is, or pwd.getpwuid(os.getuid())[0] to get the login name of the current
    real user id.

    Availability: Unix, Windows.

    os.getpgid(pid)

    Return the process group id of the process with process id pid. If pid is 0,
    the process group id of the current process is returned.

    Availability: Unix.

    os.getpgrp()

    Return the id of the current process group.

    Availability: Unix.

    os.getpid()

    Return the current process id.

    os.getppid()

    Return the parent’s process id. When the parent process has exited, on Unix
    the id returned is the one of the init process (1), on Windows it is still
    the same id, which may be already reused by another process.

    Availability: Unix, Windows.

    Changed in version 3.2: Added support for Windows.

    os.getpriority(which, who)

    Get program scheduling priority. The value which is one of
    PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who
    is interpreted relative to which (a process identifier for
    PRIO_PROCESS, process group identifier for PRIO_PGRP, and a
    user ID for PRIO_USER). A zero value for who denotes
    (respectively) the calling process, the process group of the calling process,
    or the real user ID of the calling process.

    Availability: Unix.

    New in version 3.3.

    os.PRIO_PROCESS
    os.PRIO_PGRP
    os.PRIO_USER

    Parameters for the getpriority() and setpriority() functions.

    Availability: Unix.

    New in version 3.3.

    os.getresuid()

    Return a tuple (ruid, euid, suid) denoting the current process’s
    real, effective, and saved user ids.

    Availability: Unix.

    New in version 3.2.

    os.getresgid()

    Return a tuple (rgid, egid, sgid) denoting the current process’s
    real, effective, and saved group ids.

    Availability: Unix.

    New in version 3.2.

    os.getuid()

    Return the current process’s real user id.

    Availability: Unix.

    os.initgroups(username, gid)

    Call the system initgroups() to initialize the group access list with all of
    the groups of which the specified username is a member, plus the specified
    group id.

    Availability: Unix.

    New in version 3.2.

    os.putenv(key, value)

    Set the environment variable named key to the string value. Such
    changes to the environment affect subprocesses started with os.system(),
    popen() or fork() and execv().

    Availability: most flavors of Unix, Windows.

    Note

    On some platforms, including FreeBSD and Mac OS X, setting environ may
    cause memory leaks. Refer to the system documentation for putenv.

    When putenv() is supported, assignments to items in os.environ are
    automatically translated into corresponding calls to putenv(); however,
    calls to putenv() don’t update os.environ, so it is actually
    preferable to assign to items of os.environ.

    os.setegid(egid)

    Set the current process’s effective group id.

    Availability: Unix.

    os.seteuid(euid)

    Set the current process’s effective user id.

    Availability: Unix.

    os.setgid(gid)

    Set the current process’ group id.

    Availability: Unix.

    os.setgroups(groups)

    Set the list of supplemental group ids associated with the current process to
    groups. groups must be a sequence, and each element must be an integer
    identifying a group. This operation is typically available only to the superuser.

    Availability: Unix.

    Note

    On Mac OS X, the length of groups may not exceed the
    system-defined maximum number of effective group ids, typically 16.
    See the documentation for getgroups() for cases where it may not
    return the same group list set by calling setgroups().

    os.setpgrp()

    Call the system call setpgrp() or setpgrp(0, 0) depending on
    which version is implemented (if any). See the Unix manual for the semantics.

    Availability: Unix.

    os.setpgid(pid, pgrp)

    Call the system call setpgid() to set the process group id of the
    process with id pid to the process group with id pgrp. See the Unix manual
    for the semantics.

    Availability: Unix.

    os.setpriority(which, who, priority)

    Set program scheduling priority. The value which is one of
    PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who
    is interpreted relative to which (a process identifier for
    PRIO_PROCESS, process group identifier for PRIO_PGRP, and a
    user ID for PRIO_USER). A zero value for who denotes
    (respectively) the calling process, the process group of the calling process,
    or the real user ID of the calling process.
    priority is a value in the range -20 to 19. The default priority is 0;
    lower priorities cause more favorable scheduling.

    Availability: Unix

    New in version 3.3.

    os.setregid(rgid, egid)

    Set the current process’s real and effective group ids.

    Availability: Unix.

    os.setresgid(rgid, egid, sgid)

    Set the current process’s real, effective, and saved group ids.

    Availability: Unix.

    New in version 3.2.

    os.setresuid(ruid, euid, suid)

    Set the current process’s real, effective, and saved user ids.

    Availability: Unix.

    New in version 3.2.

    os.setreuid(ruid, euid)

    Set the current process’s real and effective user ids.

    Availability: Unix.

    os.getsid(pid)

    Call the system call getsid(). See the Unix manual for the semantics.

    Availability: Unix.

    os.setsid()

    Call the system call setsid(). See the Unix manual for the semantics.

    Availability: Unix.

    os.setuid(uid)

    Set the current process’s user id.

    Availability: Unix.

    os.strerror(code)

    Return the error message corresponding to the error code in code.
    On platforms where strerror() returns NULL when given an unknown
    error number, ValueError is raised.

    os.supports_bytes_environ

    True if the native OS type of the environment is bytes (eg. False on
    Windows).

    New in version 3.2.

    os.umask(mask)

    Set the current numeric umask and return the previous umask.

    os.uname()

    Returns information identifying the current operating system.
    The return value is an object with five attributes:

    • sysname — operating system name
    • nodename — name of machine on network (implementation-defined)
    • release — operating system release
    • version — operating system version
    • machine — hardware identifier

    For backwards compatibility, this object is also iterable, behaving
    like a five-tuple containing sysname, nodename,
    release, version, and machine
    in that order.

    Some systems truncate nodename to 8 characters or to the
    leading component; a better way to get the hostname is
    socket.gethostname() or even
    socket.gethostbyaddr(socket.gethostname()).

    Availability: recent flavors of Unix.

    Changed in version 3.3: Return type changed from a tuple to a tuple-like object
    with named attributes.

    os.unsetenv(key)

    Unset (delete) the environment variable named key. Such changes to the
    environment affect subprocesses started with os.system(), popen() or
    fork() and execv().

    When unsetenv() is supported, deletion of items in os.environ is
    automatically translated into a corresponding call to unsetenv(); however,
    calls to unsetenv() don’t update os.environ, so it is actually
    preferable to delete items of os.environ.

    Availability: most flavors of Unix, Windows.

    16.1.3. File Object Creation¶

    This function creates new file objects. (See also
    open() for opening file descriptors.)

    os.fdopen(fd, *args, **kwargs)

    Return an open file object connected to the file descriptor fd. This is an
    alias of the open() built-in function and accepts the same arguments.
    The only difference is that the first argument of fdopen() must always
    be an integer.

    16.1.4. File Descriptor Operations¶

    These functions operate on I/O streams referenced using file descriptors.

    File descriptors are small integers corresponding to a file that has been opened
    by the current process. For example, standard input is usually file descriptor
    0, standard output is 1, and standard error is 2. Further files opened by a
    process will then be assigned 3, 4, 5, and so forth. The name “file descriptor”
    is slightly deceptive; on Unix platforms, sockets and pipes are also referenced
    by file descriptors.

    The fileno() method can be used to obtain the file descriptor
    associated with a file object when required. Note that using the file
    descriptor directly will bypass the file object methods, ignoring aspects such
    as internal buffering of data.

    os.close(fd)

    Close file descriptor fd.

    Note

    This function is intended for low-level I/O and must be applied to a file
    descriptor as returned by os.open() or pipe(). To close a “file
    object” returned by the built-in function open() or by popen() or
    fdopen(), use its close() method.

    os.closerange(fd_low, fd_high)

    Close all file descriptors from fd_low (inclusive) to fd_high (exclusive),
    ignoring errors. Equivalent to (but much faster than):

    for fd in range(fd_low, fd_high):
        try:
            os.close(fd)
        except OSError:
            pass
    
    os.device_encoding(fd)

    Return a string describing the encoding of the device associated with fd
    if it is connected to a terminal; else return None.

    os.dup(fd)

    Return a duplicate of file descriptor fd. The new file descriptor is
    non-inheritable.

    On Windows, when duplicating a standard stream (0: stdin, 1: stdout,
    2: stderr), the new file descriptor is inheritable.

    Changed in version 3.4: The new file descriptor is now non-inheritable.

    os.dup2(fd, fd2, inheritable=True)

    Duplicate file descriptor fd to fd2, closing the latter first if necessary.
    The file descriptor fd2 is inheritable by default,
    or non-inheritable if inheritable is False.

    Changed in version 3.4: Add the optional inheritable parameter.

    os.fchmod(fd, mode)

    Change the mode of the file given by fd to the numeric mode. See the
    docs for chmod() for possible values of mode. As of Python 3.3, this
    is equivalent to os.chmod(fd, mode).

    Availability: Unix.

    os.fchown(fd, uid, gid)

    Change the owner and group id of the file given by fd to the numeric uid
    and gid. To leave one of the ids unchanged, set it to -1. See
    chown(). As of Python 3.3, this is equivalent to os.chown(fd, uid,
    gid)
    .

    Availability: Unix.

    os.fdatasync(fd)

    Force write of file with filedescriptor fd to disk. Does not force update of
    metadata.

    Availability: Unix.

    Note

    This function is not available on MacOS.

    os.fpathconf(fd, name)

    Return system configuration information relevant to an open file. name
    specifies the configuration value to retrieve; it may be a string which is the
    name of a defined system value; these names are specified in a number of
    standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define
    additional names as well. The names known to the host operating system are
    given in the pathconf_names dictionary. For configuration variables not
    included in that mapping, passing an integer for name is also accepted.

    If name is a string and is not known, ValueError is raised. If a
    specific value for name is not supported by the host system, even if it is
    included in pathconf_names, an OSError is raised with
    errno.EINVAL for the error number.

    As of Python 3.3, this is equivalent to os.pathconf(fd, name).

    Availability: Unix.

    os.fstat(fd)

    Get the status of the file descriptor fd. Return a stat_result
    object.

    As of Python 3.3, this is equivalent to os.stat(fd).

    See also

    The stat() function.

    os.fstatvfs(fd)

    Return information about the filesystem containing the file associated with
    file descriptor fd, like statvfs(). As of Python 3.3, this is
    equivalent to os.statvfs(fd).

    Availability: Unix.

    os.fsync(fd)

    Force write of file with filedescriptor fd to disk. On Unix, this calls the
    native fsync() function; on Windows, the MS _commit() function.

    If you’re starting with a buffered Python file object f, first do
    f.flush(), and then do os.fsync(f.fileno()), to ensure that all internal
    buffers associated with f are written to disk.

    Availability: Unix, Windows.

    os.ftruncate(fd, length)

    Truncate the file corresponding to file descriptor fd, so that it is at
    most length bytes in size. As of Python 3.3, this is equivalent to
    os.truncate(fd, length).

    Availability: Unix, Windows.

    Changed in version 3.5: Added support for Windows

    os.get_blocking(fd)

    Get the blocking mode of the file descriptor: False if the
    O_NONBLOCK flag is set, True if the flag is cleared.

    See also set_blocking() and socket.socket.setblocking().

    Availability: Unix.

    New in version 3.5.

    os.isatty(fd)

    Return True if the file descriptor fd is open and connected to a
    tty(-like) device, else False.

    os.lockf(fd, cmd, len)

    Apply, test or remove a POSIX lock on an open file descriptor.
    fd is an open file descriptor.
    cmd specifies the command to use — one of F_LOCK, F_TLOCK,
    F_ULOCK or F_TEST.
    len specifies the section of the file to lock.

    Availability: Unix.

    New in version 3.3.

    os.F_LOCK
    os.F_TLOCK
    os.F_ULOCK
    os.F_TEST

    Flags that specify what action lockf() will take.

    Availability: Unix.

    New in version 3.3.

    os.lseek(fd, pos, how)

    Set the current position of file descriptor fd to position pos, modified
    by how: SEEK_SET or 0 to set the position relative to the
    beginning of the file; SEEK_CUR or 1 to set it relative to the
    current position; SEEK_END or 2 to set it relative to the end of
    the file. Return the new cursor position in bytes, starting from the beginning.

    os.SEEK_SET
    os.SEEK_CUR
    os.SEEK_END

    Parameters to the lseek() function. Their values are 0, 1, and 2,
    respectively.

    New in version 3.3: Some operating systems could support additional values, like
    os.SEEK_HOLE or os.SEEK_DATA.

    os.open(path, flags, mode=0o777, *, dir_fd=None)

    Open the file path and set various flags according to flags and possibly
    its mode according to mode. When computing mode, the current umask value
    is first masked out. Return the file descriptor for the newly opened file.
    The new file descriptor is non-inheritable.

    For a description of the flag and mode values, see the C run-time documentation;
    flag constants (like O_RDONLY and O_WRONLY) are defined in
    the os module. In particular, on Windows adding
    O_BINARY is needed to open files in binary mode.

    This function can support paths relative to directory descriptors with the dir_fd parameter.

    Changed in version 3.4: The new file descriptor is now non-inheritable.

    Note

    This function is intended for low-level I/O. For normal usage, use the
    built-in function open(), which returns a file object with
    read() and write() methods (and many more). To
    wrap a file descriptor in a file object, use fdopen().

    New in version 3.3: The dir_fd argument.

    Changed in version 3.5: If the system call is interrupted and the signal handler does not raise an
    exception, the function now retries the system call instead of raising an
    InterruptedError exception (see PEP 475 for the rationale).

    The following constants are options for the flags parameter to the
    open() function. They can be combined using the bitwise OR operator
    |. Some of them are not available on all platforms. For descriptions of
    their availability and use, consult the open(2) manual page on Unix
    or the MSDN on Windows.

    os.O_RDONLY
    os.O_WRONLY
    os.O_RDWR
    os.O_APPEND
    os.O_CREAT
    os.O_EXCL
    os.O_TRUNC

    The above constants are available on Unix and Windows.

    os.O_DSYNC
    os.O_RSYNC
    os.O_SYNC
    os.O_NDELAY
    os.O_NONBLOCK
    os.O_NOCTTY
    os.O_CLOEXEC

    The above constants are only available on Unix.

    Changed in version 3.3: Add O_CLOEXEC constant.

    os.O_BINARY
    os.O_NOINHERIT
    os.O_SHORT_LIVED
    os.O_TEMPORARY
    os.O_RANDOM
    os.O_SEQUENTIAL
    os.O_TEXT

    The above constants are only available on Windows.

    os.O_ASYNC
    os.O_DIRECT
    os.O_DIRECTORY
    os.O_NOFOLLOW
    os.O_NOATIME
    os.O_PATH
    os.O_TMPFILE
    os.O_SHLOCK
    os.O_EXLOCK

    The above constants are extensions and not present if they are not defined by
    the C library.

    Changed in version 3.4: Add O_PATH on systems that support it.
    Add O_TMPFILE, only available on Linux Kernel 3.11
    or newer.

    os.openpty()

    Open a new pseudo-terminal pair. Return a pair of file descriptors
    (master, slave) for the pty and the tty, respectively. The new file
    descriptors are non-inheritable. For a (slightly) more
    portable approach, use the pty module.

    Availability: some flavors of Unix.

    Changed in version 3.4: The new file descriptors are now non-inheritable.

    os.pipe()

    Create a pipe. Return a pair of file descriptors (r, w) usable for
    reading and writing, respectively. The new file descriptor is
    non-inheritable.

    Availability: Unix, Windows.

    Changed in version 3.4: The new file descriptors are now non-inheritable.

    os.pipe2(flags)

    Create a pipe with flags set atomically.
    flags can be constructed by ORing together one or more of these values:
    O_NONBLOCK, O_CLOEXEC.
    Return a pair of file descriptors (r, w) usable for reading and writing,
    respectively.

    Availability: some flavors of Unix.

    New in version 3.3.

    os.posix_fallocate(fd, offset, len)

    Ensures that enough disk space is allocated for the file specified by fd
    starting from offset and continuing for len bytes.

    Availability: Unix.

    New in version 3.3.

    os.posix_fadvise(fd, offset, len, advice)

    Announces an intention to access data in a specific pattern thus allowing
    the kernel to make optimizations.
    The advice applies to the region of the file specified by fd starting at
    offset and continuing for len bytes.
    advice is one of POSIX_FADV_NORMAL, POSIX_FADV_SEQUENTIAL,
    POSIX_FADV_RANDOM, POSIX_FADV_NOREUSE,
    POSIX_FADV_WILLNEED or POSIX_FADV_DONTNEED.

    Availability: Unix.

    New in version 3.3.

    os.POSIX_FADV_NORMAL
    os.POSIX_FADV_SEQUENTIAL
    os.POSIX_FADV_RANDOM
    os.POSIX_FADV_NOREUSE
    os.POSIX_FADV_WILLNEED
    os.POSIX_FADV_DONTNEED

    Flags that can be used in advice in posix_fadvise() that specify
    the access pattern that is likely to be used.

    Availability: Unix.

    New in version 3.3.

    os.pread(fd, buffersize, offset)

    Read from a file descriptor, fd, at a position of offset. It will read up
    to buffersize number of bytes. The file offset remains unchanged.

    Availability: Unix.

    New in version 3.3.

    os.pwrite(fd, str, offset)

    Write bytestring to a file descriptor, fd, from offset,
    leaving the file offset unchanged.

    Availability: Unix.

    New in version 3.3.

    os.read(fd, n)

    Read at most n bytes from file descriptor fd. Return a bytestring containing the
    bytes read. If the end of the file referred to by fd has been reached, an
    empty bytes object is returned.

    Note

    This function is intended for low-level I/O and must be applied to a file
    descriptor as returned by os.open() or pipe(). To read a
    “file object” returned by the built-in function open() or by
    popen() or fdopen(), or sys.stdin, use its
    read() or readline() methods.

    Changed in version 3.5: If the system call is interrupted and the signal handler does not raise an
    exception, the function now retries the system call instead of raising an
    InterruptedError exception (see PEP 475 for the rationale).

    os.sendfile(out, in, offset, count)
    os.sendfile(out, in, offset, count, [headers, ][trailers, ]flags=0)

    Copy count bytes from file descriptor in to file descriptor out
    starting at offset.
    Return the number of bytes sent. When EOF is reached return 0.

    The first function notation is supported by all platforms that define
    sendfile().

    On Linux, if offset is given as None, the bytes are read from the
    current position of in and the position of in is updated.

    The second case may be used on Mac OS X and FreeBSD where headers and
    trailers are arbitrary sequences of buffers that are written before and
    after the data from in is written. It returns the same as the first case.

    On Mac OS X and FreeBSD, a value of 0 for count specifies to send until
    the end of in is reached.

    All platforms support sockets as out file descriptor, and some platforms
    allow other types (e.g. regular file, pipe) as well.

    Cross-platform applications should not use headers, trailers and flags
    arguments.

    Availability: Unix.

    New in version 3.3.

    os.set_blocking(fd, blocking)

    Set the blocking mode of the specified file descriptor. Set the
    O_NONBLOCK flag if blocking is False, clear the flag otherwise.

    See also get_blocking() and socket.socket.setblocking().

    Availability: Unix.

    New in version 3.5.

    os.SF_NODISKIO
    os.SF_MNOWAIT
    os.SF_SYNC

    Parameters to the sendfile() function, if the implementation supports
    them.

    Availability: Unix.

    New in version 3.3.

    os.readv(fd, buffers)

    Read from a file descriptor fd into a number of mutable bytes-like
    objects
    buffers. readv() will transfer data
    into each buffer until it is full and then move on to the next buffer in the
    sequence to hold the rest of the data. readv() returns the total
    number of bytes read (which may be less than the total capacity of all the
    objects).

    Availability: Unix.

    New in version 3.3.

    os.tcgetpgrp(fd)

    Return the process group associated with the terminal given by fd (an open
    file descriptor as returned by os.open()).

    Availability: Unix.

    os.tcsetpgrp(fd, pg)

    Set the process group associated with the terminal given by fd (an open file
    descriptor as returned by os.open()) to pg.

    Availability: Unix.

    os.ttyname(fd)

    Return a string which specifies the terminal device associated with
    file descriptor fd. If fd is not associated with a terminal device, an
    exception is raised.

    Availability: Unix.

    os.write(fd, str)

    Write the bytestring in str to file descriptor fd. Return the number of
    bytes actually written.

    Note

    This function is intended for low-level I/O and must be applied to a file
    descriptor as returned by os.open() or pipe(). To write a “file
    object” returned by the built-in function open() or by popen() or
    fdopen(), or sys.stdout or sys.stderr, use its
    write() method.

    Changed in version 3.5: If the system call is interrupted and the signal handler does not raise an
    exception, the function now retries the system call instead of raising an
    InterruptedError exception (see PEP 475 for the rationale).

    os.writev(fd, buffers)

    Write the contents of buffers to file descriptor fd. buffers must be a
    sequence of bytes-like objects. Buffers are
    processed in array order. Entire contents of first buffer is written before
    proceeding to second, and so on. The operating system may set a limit
    (sysconf() value SC_IOV_MAX) on the number of buffers that can be used.

    writev() writes the contents of each object to the file descriptor
    and returns the total number of bytes written.

    Availability: Unix.

    New in version 3.3.

    16.1.4.1. Querying the size of a terminal¶

    New in version 3.3.

    os.get_terminal_size(fd=STDOUT_FILENO)

    Return the size of the terminal window as (columns, lines),
    tuple of type terminal_size.

    The optional argument fd (default STDOUT_FILENO, or standard
    output) specifies which file descriptor should be queried.

    If the file descriptor is not connected to a terminal, an OSError
    is raised.

    shutil.get_terminal_size() is the high-level function which
    should normally be used, os.get_terminal_size is the low-level
    implementation.

    Availability: Unix, Windows.

    class os.terminal_size

    A subclass of tuple, holding (columns, lines) of the terminal window size.

    columns

    Width of the terminal window in characters.

    lines

    Height of the terminal window in characters.

    16.1.4.2. Inheritance of File Descriptors¶

    New in version 3.4.

    A file descriptor has an “inheritable” flag which indicates if the file descriptor
    can be inherited by child processes. Since Python 3.4, file descriptors
    created by Python are non-inheritable by default.

    On UNIX, non-inheritable file descriptors are closed in child processes at the
    execution of a new program, other file descriptors are inherited.

    On Windows, non-inheritable handles and file descriptors are closed in child
    processes, except for standard streams (file descriptors 0, 1 and 2: stdin, stdout
    and stderr), which are always inherited. Using spawn* functions,
    all inheritable handles and all inheritable file descriptors are inherited.
    Using the subprocess module, all file descriptors except standard
    streams are closed, and inheritable handles are only inherited if the
    close_fds parameter is False.

    os.get_inheritable(fd)

    Get the “inheritable” flag of the specified file descriptor (a boolean).

    os.set_inheritable(fd, inheritable)

    Set the “inheritable” flag of the specified file descriptor.

    os.get_handle_inheritable(handle)

    Get the “inheritable” flag of the specified handle (a boolean).

    Availability: Windows.

    os.set_handle_inheritable(handle, inheritable)

    Set the “inheritable” flag of the specified handle.

    Availability: Windows.

    16.1.5. Files and Directories¶

    On some Unix platforms, many of these functions support one or more of these
    features:

    • specifying a file descriptor:
      For some functions, the path argument can be not only a string giving a path
      name, but also a file descriptor. The function will then operate on the file
      referred to by the descriptor. (For POSIX systems, Python will call the
      f... version of the function.)

      You can check whether or not path can be specified as a file descriptor on
      your platform using os.supports_fd. If it is unavailable, using it
      will raise a NotImplementedError.

      If the function also supports dir_fd or follow_symlinks arguments, it is
      an error to specify one of those when supplying path as a file descriptor.

    • paths relative to directory descriptors: If dir_fd is not None, it
      should be a file descriptor referring to a directory, and the path to operate
      on should be relative; path will then be relative to that directory. If the
      path is absolute, dir_fd is ignored. (For POSIX systems, Python will call
      the ...at or f...at version of the function.)

      You can check whether or not dir_fd is supported on your platform using
      os.supports_dir_fd. If it is unavailable, using it will raise a
      NotImplementedError.

    • not following symlinks: If follow_symlinks is
      False, and the last element of the path to operate on is a symbolic link,
      the function will operate on the symbolic link itself instead of the file the
      link points to. (For POSIX systems, Python will call the l... version of
      the function.)

      You can check whether or not follow_symlinks is supported on your platform
      using os.supports_follow_symlinks. If it is unavailable, using it
      will raise a NotImplementedError.

    os.access(path, mode, *, dir_fd=None, effective_ids=False, follow_symlinks=True)

    Use the real uid/gid to test for access to path. Note that most operations
    will use the effective uid/gid, therefore this routine can be used in a
    suid/sgid environment to test if the invoking user has the specified access to
    path. mode should be F_OK to test the existence of path, or it
    can be the inclusive OR of one or more of R_OK, W_OK, and
    X_OK to test permissions. Return True if access is allowed,
    False if not. See the Unix man page access(2) for more
    information.

    This function can support specifying paths relative to directory
    descriptors
    and not following symlinks.

    If effective_ids is True, access() will perform its access
    checks using the effective uid/gid instead of the real uid/gid.
    effective_ids may not be supported on your platform; you can check whether
    or not it is available using os.supports_effective_ids. If it is
    unavailable, using it will raise a NotImplementedError.

    Note

    Using access() to check if a user is authorized to e.g. open a file
    before actually doing so using open() creates a security hole,
    because the user might exploit the short time interval between checking
    and opening the file to manipulate it. It’s preferable to use EAFP
    techniques. For example:

    if os.access("myfile", os.R_OK):
        with open("myfile") as fp:
            return fp.read()
    return "some default data"
    

    is better written as:

    try:
        fp = open("myfile")
    except PermissionError:
        return "some default data"
    else:
        with fp:
            return fp.read()
    

    Note

    I/O operations may fail even when access() indicates that they would
    succeed, particularly for operations on network filesystems which may have
    permissions semantics beyond the usual POSIX permission-bit model.

    Changed in version 3.3: Added the dir_fd, effective_ids, and follow_symlinks parameters.

    os.F_OK
    os.R_OK
    os.W_OK
    os.X_OK

    Values to pass as the mode parameter of access() to test the
    existence, readability, writability and executability of path,
    respectively.

    os.chdir(path)

    Change the current working directory to path.

    This function can support specifying a file descriptor. The
    descriptor must refer to an opened directory, not an open file.

    New in version 3.3: Added support for specifying path as a file descriptor
    on some platforms.

    os.chflags(path, flags, *, follow_symlinks=True)

    Set the flags of path to the numeric flags. flags may take a combination
    (bitwise OR) of the following values (as defined in the stat module):

    • stat.UF_NODUMP
    • stat.UF_IMMUTABLE
    • stat.UF_APPEND
    • stat.UF_OPAQUE
    • stat.UF_NOUNLINK
    • stat.UF_COMPRESSED
    • stat.UF_HIDDEN
    • stat.SF_ARCHIVED
    • stat.SF_IMMUTABLE
    • stat.SF_APPEND
    • stat.SF_NOUNLINK
    • stat.SF_SNAPSHOT

    This function can support not following symlinks.

    Availability: Unix.

    New in version 3.3: The follow_symlinks argument.

    os.chmod(path, mode, *, dir_fd=None, follow_symlinks=True)

    Change the mode of path to the numeric mode. mode may take one of the
    following values (as defined in the stat module) or bitwise ORed
    combinations of them:

    • stat.S_ISUID
    • stat.S_ISGID
    • stat.S_ENFMT
    • stat.S_ISVTX
    • stat.S_IREAD
    • stat.S_IWRITE
    • stat.S_IEXEC
    • stat.S_IRWXU
    • stat.S_IRUSR
    • stat.S_IWUSR
    • stat.S_IXUSR
    • stat.S_IRWXG
    • stat.S_IRGRP
    • stat.S_IWGRP
    • stat.S_IXGRP
    • stat.S_IRWXO
    • stat.S_IROTH
    • stat.S_IWOTH
    • stat.S_IXOTH

    This function can support specifying a file descriptor,
    paths relative to directory descriptors and not
    following symlinks
    .

    Note

    Although Windows supports chmod(), you can only set the file’s
    read-only flag with it (via the stat.S_IWRITE and stat.S_IREAD
    constants or a corresponding integer value). All other bits are ignored.

    New in version 3.3: Added support for specifying path as an open file descriptor,
    and the dir_fd and follow_symlinks arguments.

    os.chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True)

    Change the owner and group id of path to the numeric uid and gid. To
    leave one of the ids unchanged, set it to -1.

    This function can support specifying a file descriptor,
    paths relative to directory descriptors and not
    following symlinks
    .

    See shutil.chown() for a higher-level function that accepts names in
    addition to numeric ids.

    Availability: Unix.

    New in version 3.3: Added support for specifying an open file descriptor for path,
    and the dir_fd and follow_symlinks arguments.

    os.chroot(path)

    Change the root directory of the current process to path.

    Availability: Unix.

    os.fchdir(fd)

    Change the current working directory to the directory represented by the file
    descriptor fd. The descriptor must refer to an opened directory, not an
    open file. As of Python 3.3, this is equivalent to os.chdir(fd).

    Availability: Unix.

    os.getcwd()

    Return a string representing the current working directory.

    os.getcwdb()

    Return a bytestring representing the current working directory.

    os.lchflags(path, flags)

    Set the flags of path to the numeric flags, like chflags(), but do
    not follow symbolic links. As of Python 3.3, this is equivalent to
    os.chflags(path, flags, follow_symlinks=False).

    Availability: Unix.

    os.lchmod(path, mode)

    Change the mode of path to the numeric mode. If path is a symlink, this
    affects the symlink rather than the target. See the docs for chmod()
    for possible values of mode. As of Python 3.3, this is equivalent to
    os.chmod(path, mode, follow_symlinks=False).

    Availability: Unix.

    os.lchown(path, uid, gid)

    Change the owner and group id of path to the numeric uid and gid. This
    function will not follow symbolic links. As of Python 3.3, this is equivalent
    to os.chown(path, uid, gid, follow_symlinks=False).

    Availability: Unix.

    os.link(src, dst, *, src_dir_fd=None, dst_dir_fd=None, follow_symlinks=True)

    Create a hard link pointing to src named dst.

    This function can support specifying src_dir_fd and/or dst_dir_fd to
    supply paths relative to directory descriptors, and not
    following symlinks
    .

    Availability: Unix, Windows.

    Changed in version 3.2: Added Windows support.

    New in version 3.3: Added the src_dir_fd, dst_dir_fd, and follow_symlinks arguments.

    Changed in version 3.6: Accepts a path-like object for src and dst.

    os.listdir(path=’.’)

    Return a list containing the names of the entries in the directory given by
    path. The list is in arbitrary order, and does not include the special
    entries '.' and '..' even if they are present in the directory.

    path may be a path-like object. If path is of type bytes
    (directly or indirectly through the PathLike interface),
    the filenames returned will also be of type bytes;
    in all other circumstances, they will be of type str.

    This function can also support specifying a file descriptor; the file descriptor must refer to a directory.

    Note

    To encode str filenames to bytes, use fsencode().

    See also

    The scandir() function returns directory entries along with
    file attribute information, giving better performance for many
    common use cases.

    Changed in version 3.2: The path parameter became optional.

    New in version 3.3: Added support for specifying an open file descriptor for path.

    os.lstat(path, *, dir_fd=None)

    Perform the equivalent of an lstat() system call on the given path.
    Similar to stat(), but does not follow symbolic links. Return a
    stat_result object.

    On platforms that do not support symbolic links, this is an alias for
    stat().

    As of Python 3.3, this is equivalent to os.stat(path, dir_fd=dir_fd,
    follow_symlinks=False)
    .

    This function can also support paths relative to directory descriptors.

    See also

    The stat() function.

    Changed in version 3.2: Added support for Windows 6.0 (Vista) symbolic links.

    Changed in version 3.3: Added the dir_fd parameter.

    Changed in version 3.6: Accepts a path-like object for src and dst.

    os.mkdir(path, mode=0o777, *, dir_fd=None)

    Create a directory named path with numeric mode mode.

    If the directory already exists, FileExistsError is raised.

    On some systems, mode is ignored. Where it is used, the current umask
    value is first masked out. If bits other than the last 9 (i.e. the last 3
    digits of the octal representation of the mode) are set, their meaning is
    platform-dependent. On some platforms, they are ignored and you should call
    chmod() explicitly to set them.

    This function can also support paths relative to directory descriptors.

    It is also possible to create temporary directories; see the
    tempfile module’s tempfile.mkdtemp() function.

    New in version 3.3: The dir_fd argument.

    os.makedirs(name, mode=0o777, exist_ok=False)

    Recursive directory creation function. Like mkdir(), but makes all
    intermediate-level directories needed to contain the leaf directory.

    The mode parameter is passed to mkdir() for creating the leaf
    directory; see the mkdir() description for how it
    is interpreted. To set the file permission bits of any newly-created parent
    directories you can set the umask before invoking makedirs(). The
    file permission bits of existing parent directories are not changed.

    If exist_ok is False (the default), an OSError is raised if the
    target directory already exists.

    Note

    makedirs() will become confused if the path elements to create
    include pardir (eg. ”..” on UNIX systems).

    This function handles UNC paths correctly.

    New in version 3.2: The exist_ok parameter.

    Changed in version 3.4.1: Before Python 3.4.1, if exist_ok was True and the directory existed,
    makedirs() would still raise an error if mode did not match the
    mode of the existing directory. Since this behavior was impossible to
    implement safely, it was removed in Python 3.4.1. See bpo-21082.

    Changed in version 3.7: The mode argument no longer affects the file permission bits of
    newly-created intermediate-level directories.

    os.mkfifo(path, mode=0o666, *, dir_fd=None)

    Create a FIFO (a named pipe) named path with numeric mode mode.
    The current umask value is first masked out from the mode.

    This function can also support paths relative to directory descriptors.

    FIFOs are pipes that can be accessed like regular files. FIFOs exist until they
    are deleted (for example with os.unlink()). Generally, FIFOs are used as
    rendezvous between “client” and “server” type processes: the server opens the
    FIFO for reading, and the client opens it for writing. Note that mkfifo()
    doesn’t open the FIFO — it just creates the rendezvous point.

    Availability: Unix.

    New in version 3.3: The dir_fd argument.

    os.mknod(path, mode=0o600, device=0, *, dir_fd=None)

    Create a filesystem node (file, device special file or named pipe) named
    path. mode specifies both the permissions to use and the type of node
    to be created, being combined (bitwise OR) with one of stat.S_IFREG,
    stat.S_IFCHR, stat.S_IFBLK, and stat.S_IFIFO (those constants are
    available in stat). For stat.S_IFCHR and stat.S_IFBLK,
    device defines the newly created device special file (probably using
    os.makedev()), otherwise it is ignored.

    This function can also support paths relative to directory descriptors.

    Availability: Unix.

    New in version 3.3: The dir_fd argument.

    os.major(device)

    Extract the device major number from a raw device number (usually the
    st_dev or st_rdev field from stat).

    os.minor(device)

    Extract the device minor number from a raw device number (usually the
    st_dev or st_rdev field from stat).

    os.makedev(major, minor)

    Compose a raw device number from the major and minor device numbers.

    os.pathconf(path, name)

    Return system configuration information relevant to a named file. name
    specifies the configuration value to retrieve; it may be a string which is the
    name of a defined system value; these names are specified in a number of
    standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define
    additional names as well. The names known to the host operating system are
    given in the pathconf_names dictionary. For configuration variables not
    included in that mapping, passing an integer for name is also accepted.

    If name is a string and is not known, ValueError is raised. If a
    specific value for name is not supported by the host system, even if it is
    included in pathconf_names, an OSError is raised with
    errno.EINVAL for the error number.

    This function can support specifying a file descriptor.

    Availability: Unix.

    os.pathconf_names

    Dictionary mapping names accepted by pathconf() and fpathconf() to
    the integer values defined for those names by the host operating system. This
    can be used to determine the set of names known to the system.

    Availability: Unix.

    os.readlink(path, *, dir_fd=None)

    Return a string representing the path to which the symbolic link points. The
    result may be either an absolute or relative pathname; if it is relative, it
    may be converted to an absolute pathname using
    os.path.join(os.path.dirname(path), result).

    If the path is a string object (directly or indirectly through a
    PathLike interface), the result will also be a string object,
    and the call may raise a UnicodeDecodeError. If the path is a bytes
    object (direct or indirectly), the result will be a bytes object.

    This function can also support paths relative to directory descriptors.

    Availability: Unix, Windows

    Changed in version 3.2: Added support for Windows 6.0 (Vista) symbolic links.

    New in version 3.3: The dir_fd argument.

    os.remove(path, *, dir_fd=None)

    Remove (delete) the file path. If path is a directory, OSError is
    raised. Use rmdir() to remove directories.

    This function can support paths relative to directory descriptors.

    On Windows, attempting to remove a file that is in use causes an exception to
    be raised; on Unix, the directory entry is removed but the storage allocated
    to the file is not made available until the original file is no longer in use.

    This function is semantically identical to unlink().

    New in version 3.3: The dir_fd argument.

    os.removedirs(name)

    Remove directories recursively. Works like rmdir() except that, if the
    leaf directory is successfully removed, removedirs() tries to
    successively remove every parent directory mentioned in path until an error
    is raised (which is ignored, because it generally means that a parent directory
    is not empty). For example, os.removedirs('foo/bar/baz') will first remove
    the directory 'foo/bar/baz', and then remove 'foo/bar' and 'foo' if
    they are empty. Raises OSError if the leaf directory could not be
    successfully removed.

    os.rename(src, dst, *, src_dir_fd=None, dst_dir_fd=None)

    Rename the file or directory src to dst. If dst is a directory,
    OSError will be raised. On Unix, if dst exists and is a file, it will
    be replaced silently if the user has permission. The operation may fail on some
    Unix flavors if src and dst are on different filesystems. If successful,
    the renaming will be an atomic operation (this is a POSIX requirement). On
    Windows, if dst already exists, OSError will be raised even if it is a
    file.

    This function can support specifying src_dir_fd and/or dst_dir_fd to
    supply paths relative to directory descriptors.

    If you want cross-platform overwriting of the destination, use replace().

    New in version 3.3: The src_dir_fd and dst_dir_fd arguments.

    Changed in version 3.6: Accepts a path-like object for src and dst.

    os.renames(old, new)

    Recursive directory or file renaming function. Works like rename(), except
    creation of any intermediate directories needed to make the new pathname good is
    attempted first. After the rename, directories corresponding to rightmost path
    segments of the old name will be pruned away using removedirs().

    Note

    This function can fail with the new directory structure made if you lack
    permissions needed to remove the leaf directory or file.

    Changed in version 3.6: Accepts a path-like object for old and new.

    os.replace(src, dst, *, src_dir_fd=None, dst_dir_fd=None)

    Rename the file or directory src to dst. If dst is a directory,
    OSError will be raised. If dst exists and is a file, it will
    be replaced silently if the user has permission. The operation may fail
    if src and dst are on different filesystems. If successful,
    the renaming will be an atomic operation (this is a POSIX requirement).

    This function can support specifying src_dir_fd and/or dst_dir_fd to
    supply paths relative to directory descriptors.

    New in version 3.3.

    Changed in version 3.6: Accepts a path-like object for src and dst.

    os.rmdir(path, *, dir_fd=None)

    Remove (delete) the directory path. Only works when the directory is
    empty, otherwise, OSError is raised. In order to remove whole
    directory trees, shutil.rmtree() can be used.

    This function can support paths relative to directory descriptors.

    New in version 3.3: The dir_fd parameter.

    os.scandir(path=’.’)

    Return an iterator of os.DirEntry objects corresponding to the
    entries in the directory given by path. The entries are yielded in
    arbitrary order, and the special entries '.' and '..' are not
    included.

    Using scandir() instead of listdir() can significantly
    increase the performance of code that also needs file type or file
    attribute information, because os.DirEntry objects expose this
    information if the operating system provides it when scanning a directory.
    All os.DirEntry methods may perform a system call, but
    is_dir() and is_file() usually only
    require a system call for symbolic links; os.DirEntry.stat()
    always requires a system call on Unix but only requires one for
    symbolic links on Windows.

    path may be a path-like object. If path is of type bytes
    (directly or indirectly through the PathLike interface),
    the type of the name and path
    attributes of each os.DirEntry will be bytes; in all other
    circumstances, they will be of type str.

    This function can also support specifying a file descriptor; the file descriptor must refer to a directory.

    The scandir() iterator supports the context manager protocol
    and has the following method:

    scandir.close()

    Close the iterator and free acquired resources.

    This is called automatically when the iterator is exhausted or garbage
    collected, or when an error happens during iterating. However it
    is advisable to call it explicitly or use the with
    statement.

    New in version 3.6.

    The following example shows a simple use of scandir() to display all
    the files (excluding directories) in the given path that don’t start with
    '.'. The entry.is_file() call will generally not make an additional
    system call:

    with os.scandir(path) as it:
        for entry in it:
            if not entry.name.startswith('.') and entry.is_file():
                print(entry.name)
    

    New in version 3.5.

    Changed in version 3.7: Added support for file descriptors on Unix.

    class os.DirEntry

    Object yielded by scandir() to expose the file path and other file
    attributes of a directory entry.

    scandir() will provide as much of this information as possible without
    making additional system calls. When a stat() or lstat() system call
    is made, the os.DirEntry object will cache the result.

    os.DirEntry instances are not intended to be stored in long-lived data
    structures; if you know the file metadata has changed or if a long time has
    elapsed since calling scandir(), call os.stat(entry.path) to fetch
    up-to-date information.

    Because the os.DirEntry methods can make operating system calls, they may
    also raise OSError. If you need very fine-grained
    control over errors, you can catch OSError when calling one of the
    os.DirEntry methods and handle as appropriate.

    To be directly usable as a path-like object, os.DirEntry
    implements the PathLike interface.

    Attributes and methods on a os.DirEntry instance are as follows:

    name

    The entry’s base filename, relative to the scandir() path
    argument.

    The name attribute will be bytes if the scandir()
    path argument is of type bytes and str otherwise. Use
    fsdecode() to decode byte filenames.

    path

    The entry’s full path name: equivalent to os.path.join(scandir_path,
    entry.name)
    where scandir_path is the scandir() path
    argument. The path is only absolute if the scandir() path
    argument was absolute. If the scandir() path
    argument was a file descriptor, the path
    attribute is the same as the name attribute.

    The path attribute will be bytes if the scandir()
    path argument is of type bytes and str otherwise. Use
    fsdecode() to decode byte filenames.

    inode()

    Return the inode number of the entry.

    The result is cached on the os.DirEntry object. Use
    os.stat(entry.path, follow_symlinks=False).st_ino to fetch up-to-date
    information.

    On the first, uncached call, a system call is required on Windows but
    not on Unix.

    is_dir(*, follow_symlinks=True)

    Return True if this entry is a directory or a symbolic link pointing
    to a directory; return False if the entry is or points to any other
    kind of file, or if it doesn’t exist anymore.

    If follow_symlinks is False, return True only if this entry
    is a directory (without following symlinks); return False if the
    entry is any other kind of file or if it doesn’t exist anymore.

    The result is cached on the os.DirEntry object, with a separate cache
    for follow_symlinks True and False. Call os.stat() along
    with stat.S_ISDIR() to fetch up-to-date information.

    On the first, uncached call, no system call is required in most cases.
    Specifically, for non-symlinks, neither Windows or Unix require a system
    call, except on certain Unix file systems, such as network file systems,
    that return dirent.d_type == DT_UNKNOWN. If the entry is a symlink,
    a system call will be required to follow the symlink unless
    follow_symlinks is False.

    This method can raise OSError, such as PermissionError,
    but FileNotFoundError is caught and not raised.

    is_file(*, follow_symlinks=True)

    Return True if this entry is a file or a symbolic link pointing to a
    file; return False if the entry is or points to a directory or other
    non-file entry, or if it doesn’t exist anymore.

    If follow_symlinks is False, return True only if this entry
    is a file (without following symlinks); return False if the entry is
    a directory or other non-file entry, or if it doesn’t exist anymore.

    The result is cached on the os.DirEntry object. Caching, system calls
    made, and exceptions raised are as per is_dir().

    is_symlink()

    Return True if this entry is a symbolic link (even if broken);
    return False if the entry points to a directory or any kind of file,
    or if it doesn’t exist anymore.

    The result is cached on the os.DirEntry object. Call
    os.path.islink() to fetch up-to-date information.

    On the first, uncached call, no system call is required in most cases.
    Specifically, neither Windows or Unix require a system call, except on
    certain Unix file systems, such as network file systems, that return
    dirent.d_type == DT_UNKNOWN.

    This method can raise OSError, such as PermissionError,
    but FileNotFoundError is caught and not raised.

    stat(*, follow_symlinks=True)

    Return a stat_result object for this entry. This method
    follows symbolic links by default; to stat a symbolic link add the
    follow_symlinks=False argument.

    On Unix, this method always requires a system call. On Windows, it
    only requires a system call if follow_symlinks is True and the
    entry is a symbolic link.

    On Windows, the st_ino, st_dev and st_nlink attributes of the
    stat_result are always set to zero. Call os.stat() to
    get these attributes.

    The result is cached on the os.DirEntry object, with a separate cache
    for follow_symlinks True and False. Call os.stat() to
    fetch up-to-date information.

    Note that there is a nice correspondence between several attributes
    and methods of os.DirEntry and of pathlib.Path. In
    particular, the name attribute has the same
    meaning, as do the is_dir(), is_file(), is_symlink()
    and stat() methods.

    New in version 3.5.

    Changed in version 3.6: Added support for the PathLike interface. Added support
    for bytes paths on Windows.

    os.stat(path, *, dir_fd=None, follow_symlinks=True)

    Get the status of a file or a file descriptor. Perform the equivalent of a
    stat() system call on the given path. path may be specified as
    either a string or bytes – directly or indirectly through the PathLike
    interface – or as an open file descriptor. Return a stat_result
    object.

    This function normally follows symlinks; to stat a symlink add the argument
    follow_symlinks=False, or use lstat().

    This function can support specifying a file descriptor and
    not following symlinks.

    Example:

    >>> import os
    >>> statinfo = os.stat('somefile.txt')
    >>> statinfo
    os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
    st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
    st_mtime=1297230027, st_ctime=1297230027)
    >>> statinfo.st_size
    264
    

    See also

    fstat() and lstat() functions.

    New in version 3.3: Added the dir_fd and follow_symlinks arguments, specifying a file
    descriptor instead of a path.

    class os.stat_result

    Object whose attributes correspond roughly to the members of the
    stat structure. It is used for the result of os.stat(),
    os.fstat() and os.lstat().

    Attributes:

    st_mode

    File mode: file type and file mode bits (permissions).

    st_ino

    Inode number.

    st_dev

    Identifier of the device on which this file resides.

    st_nlink

    Number of hard links.

    st_uid

    User identifier of the file owner.

    st_gid

    Group identifier of the file owner.

    st_size

    Size of the file in bytes, if it is a regular file or a symbolic link.
    The size of a symbolic link is the length of the pathname it contains,
    without a terminating null byte.

    Timestamps:

    st_atime

    Time of most recent access expressed in seconds.

    st_mtime

    Time of most recent content modification expressed in seconds.

    st_ctime

    Platform dependent:

    • the time of most recent metadata change on Unix,
    • the time of creation on Windows, expressed in seconds.
    st_atime_ns

    Time of most recent access expressed in nanoseconds as an integer.

    st_mtime_ns

    Time of most recent content modification expressed in nanoseconds as an
    integer.

    st_ctime_ns

    Platform dependent:

    • the time of most recent metadata change on Unix,
    • the time of creation on Windows, expressed in nanoseconds as an
      integer.

    Note

    The exact meaning and resolution of the st_atime,
    st_mtime, and st_ctime attributes depend on the operating
    system and the file system. For example, on Windows systems using the FAT
    or FAT32 file systems, st_mtime has 2-second resolution, and
    st_atime has only 1-day resolution. See your operating system
    documentation for details.

    Similarly, although st_atime_ns, st_mtime_ns,
    and st_ctime_ns are always expressed in nanoseconds, many
    systems do not provide nanosecond precision. On systems that do
    provide nanosecond precision, the floating-point object used to
    store st_atime, st_mtime, and st_ctime
    cannot preserve all of it, and as such will be slightly inexact.
    If you need the exact timestamps you should always use
    st_atime_ns, st_mtime_ns, and st_ctime_ns.

    On some Unix systems (such as Linux), the following attributes may also be
    available:

    st_blocks

    Number of 512-byte blocks allocated for file.
    This may be smaller than st_size/512 when the file has holes.

    st_blksize

    “Preferred” blocksize for efficient file system I/O. Writing to a file in
    smaller chunks may cause an inefficient read-modify-rewrite.

    st_rdev

    Type of device if an inode device.

    st_flags

    User defined flags for file.

    On other Unix systems (such as FreeBSD), the following attributes may be
    available (but may be only filled out if root tries to use them):

    st_gen

    File generation number.

    st_birthtime

    Time of file creation.

    On Mac OS systems, the following attributes may also be available:

    st_rsize

    Real size of the file.

    st_creator

    Creator of the file.

    st_type

    File type.

    On Windows systems, the following attribute is also available:

    st_file_attributes

    Windows file attributes: dwFileAttributes member of the
    BY_HANDLE_FILE_INFORMATION structure returned by
    GetFileInformationByHandle(). See the FILE_ATTRIBUTE_*
    constants in the stat module.

    The standard module stat defines functions and constants that are
    useful for extracting information from a stat structure. (On
    Windows, some items are filled with dummy values.)

    For backward compatibility, a stat_result instance is also
    accessible as a tuple of at least 10 integers giving the most important (and
    portable) members of the stat structure, in the order
    st_mode, st_ino, st_dev, st_nlink,
    st_uid, st_gid, st_size, st_atime,
    st_mtime, st_ctime. More items may be added at the end by
    some implementations. For compatibility with older Python versions,
    accessing stat_result as a tuple always returns integers.

    New in version 3.3: Added the st_atime_ns, st_mtime_ns, and
    st_ctime_ns members.

    New in version 3.5: Added the st_file_attributes member on Windows.

    os.statvfs(path)

    Perform a statvfs() system call on the given path. The return value is
    an object whose attributes describe the filesystem on the given path, and
    correspond to the members of the statvfs structure, namely:
    f_bsize, f_frsize, f_blocks, f_bfree,
    f_bavail, f_files, f_ffree, f_favail,
    f_flag, f_namemax.

    Two module-level constants are defined for the f_flag attribute’s
    bit-flags: if ST_RDONLY is set, the filesystem is mounted
    read-only, and if ST_NOSUID is set, the semantics of
    setuid/setgid bits are disabled or not supported.

    Additional module-level constants are defined for GNU/glibc based systems.
    These are ST_NODEV (disallow access to device special files),
    ST_NOEXEC (disallow program execution), ST_SYNCHRONOUS
    (writes are synced at once), ST_MANDLOCK (allow mandatory locks on an FS),
    ST_WRITE (write on file/directory/symlink), ST_APPEND
    (append-only file), ST_IMMUTABLE (immutable file), ST_NOATIME
    (do not update access times), ST_NODIRATIME (do not update directory access
    times), ST_RELATIME (update atime relative to mtime/ctime).

    This function can support specifying a file descriptor.

    Availability: Unix.

    Changed in version 3.2: The ST_RDONLY and ST_NOSUID constants were added.

    New in version 3.3: Added support for specifying an open file descriptor for path.

    Changed in version 3.4: The ST_NODEV, ST_NOEXEC, ST_SYNCHRONOUS,
    ST_MANDLOCK, ST_WRITE, ST_APPEND,
    ST_IMMUTABLE, ST_NOATIME, ST_NODIRATIME,
    and ST_RELATIME constants were added.

    os.supports_dir_fd

    A Set object indicating which functions in the
    os module permit use of their dir_fd parameter. Different platforms
    provide different functionality, and an option that might work on one might
    be unsupported on another. For consistency’s sakes, functions that support
    dir_fd always allow specifying the parameter, but will raise an exception
    if the functionality is not actually available.

    To check whether a particular function permits use of its dir_fd
    parameter, use the in operator on supports_dir_fd. As an example,
    this expression determines whether the dir_fd parameter of os.stat()
    is locally available:

    os.stat in os.supports_dir_fd
    

    Currently dir_fd parameters only work on Unix platforms; none of them work
    on Windows.

    New in version 3.3.

    os.supports_effective_ids

    A Set object indicating which functions in the
    os module permit use of the effective_ids parameter for
    os.access(). If the local platform supports it, the collection will
    contain os.access(), otherwise it will be empty.

    To check whether you can use the effective_ids parameter for
    os.access(), use the in operator on supports_effective_ids,
    like so:

    os.access in os.supports_effective_ids
    

    Currently effective_ids only works on Unix platforms; it does not work on
    Windows.

    New in version 3.3.

    os.supports_fd

    A Set object indicating which functions in the
    os module permit specifying their path parameter as an open file
    descriptor. Different platforms provide different functionality, and an
    option that might work on one might be unsupported on another. For
    consistency’s sakes, functions that support fd always allow specifying
    the parameter, but will raise an exception if the functionality is not
    actually available.

    To check whether a particular function permits specifying an open file
    descriptor for its path parameter, use the in operator on
    supports_fd. As an example, this expression determines whether
    os.chdir() accepts open file descriptors when called on your local
    platform:

    os.chdir in os.supports_fd
    

    New in version 3.3.

    os.supports_follow_symlinks

    A Set object indicating which functions in the
    os module permit use of their follow_symlinks parameter. Different
    platforms provide different functionality, and an option that might work on
    one might be unsupported on another. For consistency’s sakes, functions that
    support follow_symlinks always allow specifying the parameter, but will
    raise an exception if the functionality is not actually available.

    To check whether a particular function permits use of its follow_symlinks
    parameter, use the in operator on supports_follow_symlinks. As an
    example, this expression determines whether the follow_symlinks parameter
    of os.stat() is locally available:

    os.stat in os.supports_follow_symlinks
    

    New in version 3.3.

    os.symlink(src, dst, target_is_directory=False, *, dir_fd=None)

    Create a symbolic link pointing to src named dst.

    On Windows, a symlink represents either a file or a directory, and does not
    morph to the target dynamically. If the target is present, the type of the
    symlink will be created to match. Otherwise, the symlink will be created
    as a directory if target_is_directory is True or a file symlink (the
    default) otherwise. On non-Window platforms, target_is_directory is ignored.

    Symbolic link support was introduced in Windows 6.0 (Vista). symlink()
    will raise a NotImplementedError on Windows versions earlier than 6.0.

    This function can support paths relative to directory descriptors.

    Note

    On Windows, the SeCreateSymbolicLinkPrivilege is required in order to
    successfully create symlinks. This privilege is not typically granted to
    regular users but is available to accounts which can escalate privileges
    to the administrator level. Either obtaining the privilege or running your
    application as an administrator are ways to successfully create symlinks.

    OSError is raised when the function is called by an unprivileged
    user.

    Availability: Unix, Windows.

    Changed in version 3.2: Added support for Windows 6.0 (Vista) symbolic links.

    New in version 3.3: Added the dir_fd argument, and now allow target_is_directory
    on non-Windows platforms.

    Changed in version 3.6: Accepts a path-like object for src and dst.

    os.sync()

    Force write of everything to disk.

    Availability: Unix.

    New in version 3.3.

    os.truncate(path, length)

    Truncate the file corresponding to path, so that it is at most
    length bytes in size.

    This function can support specifying a file descriptor.

    Availability: Unix, Windows.

    New in version 3.3.

    Changed in version 3.5: Added support for Windows

    os.unlink(path, *, dir_fd=None)

    Remove (delete) the file path. This function is semantically
    identical to remove(); the unlink name is its
    traditional Unix name. Please see the documentation for
    remove() for further information.

    New in version 3.3: The dir_fd parameter.

    os.utime(path, times=None, *, [ns, ]dir_fd=None, follow_symlinks=True)

    Set the access and modified times of the file specified by path.

    utime() takes two optional parameters, times and ns.
    These specify the times set on path and are used as follows:

    • If ns is specified,
      it must be a 2-tuple of the form (atime_ns, mtime_ns)
      where each member is an int expressing nanoseconds.
    • If times is not None,
      it must be a 2-tuple of the form (atime, mtime)
      where each member is an int or float expressing seconds.
    • If times is None and ns is unspecified,
      this is equivalent to specifying ns=(atime_ns, mtime_ns)
      where both times are the current time.

    It is an error to specify tuples for both times and ns.

    Whether a directory can be given for path
    depends on whether the operating system implements directories as files
    (for example, Windows does not). Note that the exact times you set here may
    not be returned by a subsequent stat() call, depending on the
    resolution with which your operating system records access and modification
    times; see stat(). The best way to preserve exact times is to
    use the st_atime_ns and st_mtime_ns fields from the os.stat()
    result object with the ns parameter to utime.

    This function can support specifying a file descriptor,
    paths relative to directory descriptors and not
    following symlinks
    .

    New in version 3.3: Added support for specifying an open file descriptor for path,
    and the dir_fd, follow_symlinks, and ns parameters.

    os.walk(top, topdown=True, onerror=None, followlinks=False)

    Generate the file names in a directory tree by walking the tree
    either top-down or bottom-up. For each directory in the tree rooted at directory
    top (including top itself), it yields a 3-tuple (dirpath, dirnames,
    filenames)
    .

    dirpath is a string, the path to the directory. dirnames is a list of the
    names of the subdirectories in dirpath (excluding '.' and '..').
    filenames is a list of the names of the non-directory files in dirpath.
    Note that the names in the lists contain no path components. To get a full path
    (which begins with top) to a file or directory in dirpath, do
    os.path.join(dirpath, name).

    If optional argument topdown is True or not specified, the triple for a
    directory is generated before the triples for any of its subdirectories
    (directories are generated top-down). If topdown is False, the triple
    for a directory is generated after the triples for all of its subdirectories
    (directories are generated bottom-up). No matter the value of topdown, the
    list of subdirectories is retrieved before the tuples for the directory and
    its subdirectories are generated.

    When topdown is True, the caller can modify the dirnames list in-place
    (perhaps using del or slice assignment), and walk() will only
    recurse into the subdirectories whose names remain in dirnames; this can be
    used to prune the search, impose a specific order of visiting, or even to inform
    walk() about directories the caller creates or renames before it resumes
    walk() again. Modifying dirnames when topdown is False has
    no effect on the behavior of the walk, because in bottom-up mode the directories
    in dirnames are generated before dirpath itself is generated.

    By default, errors from the listdir() call are ignored. If optional
    argument onerror is specified, it should be a function; it will be called with
    one argument, an OSError instance. It can report the error to continue
    with the walk, or raise the exception to abort the walk. Note that the filename
    is available as the filename attribute of the exception object.

    By default, walk() will not walk down into symbolic links that resolve to
    directories. Set followlinks to True to visit directories pointed to by
    symlinks, on systems that support them.

    Note

    Be aware that setting followlinks to True can lead to infinite
    recursion if a link points to a parent directory of itself. walk()
    does not keep track of the directories it visited already.

    Note

    If you pass a relative pathname, don’t change the current working directory
    between resumptions of walk(). walk() never changes the current
    directory, and assumes that its caller doesn’t either.

    This example displays the number of bytes taken by non-directory files in each
    directory under the starting directory, except that it doesn’t look under any
    CVS subdirectory:

    import os
    from os.path import join, getsize
    for root, dirs, files in os.walk('python/Lib/email'):
        print(root, "consumes", end=" ")
        print(sum(getsize(join(root, name)) for name in files), end=" ")
        print("bytes in", len(files), "non-directory files")
        if 'CVS' in dirs:
            dirs.remove('CVS')  # don't visit CVS directories
    

    In the next example (simple implementation of shutil.rmtree()),
    walking the tree bottom-up is essential, rmdir() doesn’t allow
    deleting a directory before the directory is empty:

    # Delete everything reachable from the directory named in "top",
    # assuming there are no symbolic links.
    # CAUTION:  This is dangerous!  For example, if top == '/', it
    # could delete all your disk files.
    import os
    for root, dirs, files in os.walk(top, topdown=False):
        for name in files:
            os.remove(os.path.join(root, name))
        for name in dirs:
            os.rmdir(os.path.join(root, name))
    

    Changed in version 3.5: This function now calls os.scandir() instead of os.listdir(),
    making it faster by reducing the number of calls to os.stat().

    os.fwalk(top=’.’, topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=None)

    This behaves exactly like walk(), except that it yields a 4-tuple
    (dirpath, dirnames, filenames, dirfd), and it supports dir_fd.

    dirpath, dirnames and filenames are identical to walk() output,
    and dirfd is a file descriptor referring to the directory dirpath.

    This function always supports paths relative to directory descriptors and not following symlinks. Note however
    that, unlike other functions, the fwalk() default value for
    follow_symlinks is False.

    Note

    Since fwalk() yields file descriptors, those are only valid until
    the next iteration step, so you should duplicate them (e.g. with
    dup()) if you want to keep them longer.

    This example displays the number of bytes taken by non-directory files in each
    directory under the starting directory, except that it doesn’t look under any
    CVS subdirectory:

    import os
    for root, dirs, files, rootfd in os.fwalk('python/Lib/email'):
        print(root, "consumes", end="")
        print(sum([os.stat(name, dir_fd=rootfd).st_size for name in files]),
              end="")
        print("bytes in", len(files), "non-directory files")
        if 'CVS' in dirs:
            dirs.remove('CVS')  # don't visit CVS directories
    

    In the next example, walking the tree bottom-up is essential:
    rmdir() doesn’t allow deleting a directory before the directory is
    empty:

    # Delete everything reachable from the directory named in "top",
    # assuming there are no symbolic links.
    # CAUTION:  This is dangerous!  For example, if top == '/', it
    # could delete all your disk files.
    import os
    for root, dirs, files, rootfd in os.fwalk(top, topdown=False):
        for name in files:
            os.unlink(name, dir_fd=rootfd)
        for name in dirs:
            os.rmdir(name, dir_fd=rootfd)
    

    Availability: Unix.

    New in version 3.3.

    Changed in version 3.7: Added support for bytes paths.

    16.1.5.1. Linux extended attributes¶

    New in version 3.3.

    These functions are all available on Linux only.

    os.getxattr(path, attribute, *, follow_symlinks=True)

    Return the value of the extended filesystem attribute attribute for
    path. attribute can be bytes or str (directly or indirectly through the
    PathLike interface). If it is str, it is encoded with the filesystem
    encoding.

    This function can support specifying a file descriptor and
    not following symlinks.

    Changed in version 3.6: Accepts a path-like object for path and attribute.

    os.listxattr(path=None, *, follow_symlinks=True)

    Return a list of the extended filesystem attributes on path. The
    attributes in the list are represented as strings decoded with the filesystem
    encoding. If path is None, listxattr() will examine the current
    directory.

    This function can support specifying a file descriptor and
    not following symlinks.

    os.removexattr(path, attribute, *, follow_symlinks=True)

    Removes the extended filesystem attribute attribute from path.
    attribute should be bytes or str (directly or indirectly through the
    PathLike interface). If it is a string, it is encoded
    with the filesystem encoding.

    This function can support specifying a file descriptor and
    not following symlinks.

    Changed in version 3.6: Accepts a path-like object for path and attribute.

    os.setxattr(path, attribute, value, flags=0, *, follow_symlinks=True)

    Set the extended filesystem attribute attribute on path to value.
    attribute must be a bytes or str with no embedded NULs (directly or
    indirectly through the PathLike interface). If it is a str,
    it is encoded with the filesystem encoding. flags may be
    XATTR_REPLACE or XATTR_CREATE. If XATTR_REPLACE is
    given and the attribute does not exist, EEXISTS will be raised.
    If XATTR_CREATE is given and the attribute already exists, the
    attribute will not be created and ENODATA will be raised.

    This function can support specifying a file descriptor and
    not following symlinks.

    Note

    A bug in Linux kernel versions less than 2.6.39 caused the flags argument
    to be ignored on some filesystems.

    Changed in version 3.6: Accepts a path-like object for path and attribute.

    os.XATTR_SIZE_MAX

    The maximum size the value of an extended attribute can be. Currently, this
    is 64 KiB on Linux.

    os.XATTR_CREATE

    This is a possible value for the flags argument in setxattr(). It
    indicates the operation must create an attribute.

    os.XATTR_REPLACE

    This is a possible value for the flags argument in setxattr(). It
    indicates the operation must replace an existing attribute.

    16.1.6. Process Management¶

    These functions may be used to create and manage processes.

    The various exec* functions take a list of arguments for the new
    program loaded into the process. In each case, the first of these arguments is
    passed to the new program as its own name rather than as an argument a user may
    have typed on a command line. For the C programmer, this is the argv[0]
    passed to a program’s main(). For example, os.execv('/bin/echo',
    ['foo', 'bar'])
    will only print bar on standard output; foo will seem
    to be ignored.

    os.abort()

    Generate a SIGABRT signal to the current process. On Unix, the default
    behavior is to produce a core dump; on Windows, the process immediately returns
    an exit code of 3. Be aware that calling this function will not call the
    Python signal handler registered for SIGABRT with
    signal.signal().

    os.execl(path, arg0, arg1, )
    os.execle(path, arg0, arg1, , env)
    os.execlp(file, arg0, arg1, )
    os.execlpe(file, arg0, arg1, , env)
    os.execv(path, args)
    os.execve(path, args, env)
    os.execvp(file, args)
    os.execvpe(file, args, env)

    These functions all execute a new program, replacing the current process; they
    do not return. On Unix, the new executable is loaded into the current process,
    and will have the same process id as the caller. Errors will be reported as
    OSError exceptions.

    The current process is replaced immediately. Open file objects and
    descriptors are not flushed, so if there may be data buffered
    on these open files, you should flush them using
    sys.stdout.flush() or os.fsync() before calling an
    exec* function.

    The “l” and “v” variants of the exec* functions differ in how
    command-line arguments are passed. The “l” variants are perhaps the easiest
    to work with if the number of parameters is fixed when the code is written; the
    individual parameters simply become additional parameters to the execl*()
    functions. The “v” variants are good when the number of parameters is
    variable, with the arguments being passed in a list or tuple as the args
    parameter. In either case, the arguments to the child process should start with
    the name of the command being run, but this is not enforced.

    The variants which include a “p” near the end (execlp(),
    execlpe(), execvp(), and execvpe()) will use the
    PATH environment variable to locate the program file. When the
    environment is being replaced (using one of the exec*e variants,
    discussed in the next paragraph), the new environment is used as the source of
    the PATH variable. The other variants, execl(), execle(),
    execv(), and execve(), will not use the PATH variable to
    locate the executable; path must contain an appropriate absolute or relative
    path.

    For execle(), execlpe(), execve(), and execvpe() (note
    that these all end in “e”), the env parameter must be a mapping which is
    used to define the environment variables for the new process (these are used
    instead of the current process’ environment); the functions execl(),
    execlp(), execv(), and execvp() all cause the new process to
    inherit the environment of the current process.

    For execve() on some platforms, path may also be specified as an open
    file descriptor. This functionality may not be supported on your platform;
    you can check whether or not it is available using os.supports_fd.
    If it is unavailable, using it will raise a NotImplementedError.

    Availability: Unix, Windows.

    New in version 3.3: Added support for specifying an open file descriptor for path
    for execve().

    os._exit(n)

    Exit the process with status n, without calling cleanup handlers, flushing
    stdio buffers, etc.

    Note

    The standard way to exit is sys.exit(n). _exit() should
    normally only be used in the child process after a fork().

    The following exit codes are defined and can be used with _exit(),
    although they are not required. These are typically used for system programs
    written in Python, such as a mail server’s external command delivery program.

    Note

    Some of these may not be available on all Unix platforms, since there is some
    variation. These constants are defined where they are defined by the underlying
    platform.

    os.EX_OK

    Exit code that means no error occurred.

    Availability: Unix.

    os.EX_USAGE

    Exit code that means the command was used incorrectly, such as when the wrong
    number of arguments are given.

    Availability: Unix.

    os.EX_DATAERR

    Exit code that means the input data was incorrect.

    Availability: Unix.

    os.EX_NOINPUT

    Exit code that means an input file did not exist or was not readable.

    Availability: Unix.

    os.EX_NOUSER

    Exit code that means a specified user did not exist.

    Availability: Unix.

    os.EX_NOHOST

    Exit code that means a specified host did not exist.

    Availability: Unix.

    os.EX_UNAVAILABLE

    Exit code that means that a required service is unavailable.

    Availability: Unix.

    os.EX_SOFTWARE

    Exit code that means an internal software error was detected.

    Availability: Unix.

    os.EX_OSERR

    Exit code that means an operating system error was detected, such as the
    inability to fork or create a pipe.

    Availability: Unix.

    os.EX_OSFILE

    Exit code that means some system file did not exist, could not be opened, or had
    some other kind of error.

    Availability: Unix.

    os.EX_CANTCREAT

    Exit code that means a user specified output file could not be created.

    Availability: Unix.

    os.EX_IOERR

    Exit code that means that an error occurred while doing I/O on some file.

    Availability: Unix.

    os.EX_TEMPFAIL

    Exit code that means a temporary failure occurred. This indicates something
    that may not really be an error, such as a network connection that couldn’t be
    made during a retryable operation.

    Availability: Unix.

    os.EX_PROTOCOL

    Exit code that means that a protocol exchange was illegal, invalid, or not
    understood.

    Availability: Unix.

    os.EX_NOPERM

    Exit code that means that there were insufficient permissions to perform the
    operation (but not intended for file system problems).

    Availability: Unix.

    os.EX_CONFIG

    Exit code that means that some kind of configuration error occurred.

    Availability: Unix.

    os.EX_NOTFOUND

    Exit code that means something like “an entry was not found”.

    Availability: Unix.

    os.fork()

    Fork a child process. Return 0 in the child and the child’s process id in the
    parent. If an error occurs OSError is raised.

    Note that some platforms including FreeBSD <= 6.3 and Cygwin have
    known issues when using fork() from a thread.

    Warning

    See ssl for applications that use the SSL module with fork().

    Availability: Unix.

    os.forkpty()

    Fork a child process, using a new pseudo-terminal as the child’s controlling
    terminal. Return a pair of (pid, fd), where pid is 0 in the child, the
    new child’s process id in the parent, and fd is the file descriptor of the
    master end of the pseudo-terminal. For a more portable approach, use the
    pty module. If an error occurs OSError is raised.

    Availability: some flavors of Unix.

    os.kill(pid, sig)

    Send signal sig to the process pid. Constants for the specific signals
    available on the host platform are defined in the signal module.

    Windows: The signal.CTRL_C_EVENT and
    signal.CTRL_BREAK_EVENT signals are special signals which can
    only be sent to console processes which share a common console window,
    e.g., some subprocesses. Any other value for sig will cause the process
    to be unconditionally killed by the TerminateProcess API, and the exit code
    will be set to sig. The Windows version of kill() additionally takes
    process handles to be killed.

    See also signal.pthread_kill().

    New in version 3.2: Windows support.

    os.killpg(pgid, sig)

    Send the signal sig to the process group pgid.

    Availability: Unix.

    os.nice(increment)

    Add increment to the process’s “niceness”. Return the new niceness.

    Availability: Unix.

    os.plock(op)

    Lock program segments into memory. The value of op (defined in
    <sys/lock.h>) determines which segments are locked.

    Availability: Unix.

    os.popen(cmd, mode=’r’, buffering=-1)

    Open a pipe to or from command cmd.
    The return value is an open file object
    connected to the pipe, which can be read or written depending on whether mode
    is 'r' (default) or 'w'. The buffering argument has the same meaning as
    the corresponding argument to the built-in open() function. The
    returned file object reads or writes text strings rather than bytes.

    The close method returns None if the subprocess exited
    successfully, or the subprocess’s return code if there was an
    error. On POSIX systems, if the return code is positive it
    represents the return value of the process left-shifted by one
    byte. If the return code is negative, the process was terminated
    by the signal given by the negated value of the return code. (For
    example, the return value might be - signal.SIGKILL if the
    subprocess was killed.) On Windows systems, the return value
    contains the signed integer return code from the child process.

    This is implemented using subprocess.Popen; see that class’s
    documentation for more powerful ways to manage and communicate with
    subprocesses.

    os.register_at_fork(*, before=None, after_in_parent=None, after_in_child=None)

    Register callables to be executed when a new child process is forked
    using os.fork() or similar process cloning APIs.
    The parameters are optional and keyword-only.
    Each specifies a different call point.

    • before is a function called before forking a child process.
    • after_in_parent is a function called from the parent process
      after forking a child process.
    • after_in_child is a function called from the child process.

    These calls are only made if control is expected to return to the
    Python interpreter. A typical subprocess launch will not
    trigger them as the child is not going to re-enter the interpreter.

    Functions registered for execution before forking are called in
    reverse registration order. Functions registered for execution
    after forking (either in the parent or in the child) are called
    in registration order.

    Note that fork() calls made by third-party C code may not
    call those functions, unless it explicitly calls PyOS_BeforeFork(),
    PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

    There is no way to unregister a function.

    Availability: Unix.

    New in version 3.7.

    os.spawnl(mode, path, )
    os.spawnle(mode, path, , env)
    os.spawnlp(mode, file, )
    os.spawnlpe(mode, file, , env)
    os.spawnv(mode, path, args)
    os.spawnve(mode, path, args, env)
    os.spawnvp(mode, file, args)
    os.spawnvpe(mode, file, args, env)

    Execute the program path in a new process.

    (Note that the subprocess module provides more powerful facilities for
    spawning new processes and retrieving their results; using that module is
    preferable to using these functions. Check especially the
    Replacing Older Functions with the subprocess Module section.)

    If mode is P_NOWAIT, this function returns the process id of the new
    process; if mode is P_WAIT, returns the process’s exit code if it
    exits normally, or -signal, where signal is the signal that killed the
    process. On Windows, the process id will actually be the process handle, so can
    be used with the waitpid() function.

    The “l” and “v” variants of the spawn* functions differ in how
    command-line arguments are passed. The “l” variants are perhaps the easiest
    to work with if the number of parameters is fixed when the code is written; the
    individual parameters simply become additional parameters to the
    spawnl*() functions. The “v” variants are good when the number of
    parameters is variable, with the arguments being passed in a list or tuple as
    the args parameter. In either case, the arguments to the child process must
    start with the name of the command being run.

    The variants which include a second “p” near the end (spawnlp(),
    spawnlpe(), spawnvp(), and spawnvpe()) will use the
    PATH environment variable to locate the program file. When the
    environment is being replaced (using one of the spawn*e variants,
    discussed in the next paragraph), the new environment is used as the source of
    the PATH variable. The other variants, spawnl(),
    spawnle(), spawnv(), and spawnve(), will not use the
    PATH variable to locate the executable; path must contain an
    appropriate absolute or relative path.

    For spawnle(), spawnlpe(), spawnve(), and spawnvpe()
    (note that these all end in “e”), the env parameter must be a mapping
    which is used to define the environment variables for the new process (they are
    used instead of the current process’ environment); the functions
    spawnl(), spawnlp(), spawnv(), and spawnvp() all cause
    the new process to inherit the environment of the current process. Note that
    keys and values in the env dictionary must be strings; invalid keys or
    values will cause the function to fail, with a return value of 127.

    As an example, the following calls to spawnlp() and spawnvpe() are
    equivalent:

    import os
    os.spawnlp(os.P_WAIT, 'cp', 'cp', 'index.html', '/dev/null')
    
    L = ['cp', 'index.html', '/dev/null']
    os.spawnvpe(os.P_WAIT, 'cp', L, os.environ)
    

    Availability: Unix, Windows. spawnlp(), spawnlpe(), spawnvp()
    and spawnvpe() are not available on Windows. spawnle() and
    spawnve() are not thread-safe on Windows; we advise you to use the
    subprocess module instead.

    os.P_NOWAIT
    os.P_NOWAITO

    Possible values for the mode parameter to the spawn* family of
    functions. If either of these values is given, the spawn*() functions
    will return as soon as the new process has been created, with the process id as
    the return value.

    Availability: Unix, Windows.

    os.P_WAIT

    Possible value for the mode parameter to the spawn* family of
    functions. If this is given as mode, the spawn*() functions will not
    return until the new process has run to completion and will return the exit code
    of the process the run is successful, or -signal if a signal kills the
    process.

    Availability: Unix, Windows.

    os.P_DETACH
    os.P_OVERLAY

    Possible values for the mode parameter to the spawn* family of
    functions. These are less portable than those listed above. P_DETACH
    is similar to P_NOWAIT, but the new process is detached from the
    console of the calling process. If P_OVERLAY is used, the current
    process will be replaced; the spawn* function will not return.

    Availability: Windows.

    os.startfile(path[, operation])

    Start a file with its associated application.

    When operation is not specified or 'open', this acts like double-clicking
    the file in Windows Explorer, or giving the file name as an argument to the
    start command from the interactive command shell: the file is opened
    with whatever application (if any) its extension is associated.

    When another operation is given, it must be a “command verb” that specifies
    what should be done with the file. Common verbs documented by Microsoft are
    'print' and 'edit' (to be used on files) as well as 'explore' and
    'find' (to be used on directories).

    startfile() returns as soon as the associated application is launched.
    There is no option to wait for the application to close, and no way to retrieve
    the application’s exit status. The path parameter is relative to the current
    directory. If you want to use an absolute path, make sure the first character
    is not a slash ('/'); the underlying Win32 ShellExecute() function
    doesn’t work if it is. Use the os.path.normpath() function to ensure that
    the path is properly encoded for Win32.

    To reduce interpreter startup overhead, the Win32 ShellExecute()
    function is not resolved until this function is first called. If the function
    cannot be resolved, NotImplementedError will be raised.

    Availability: Windows.

    os.system(command)

    Execute the command (a string) in a subshell. This is implemented by calling
    the Standard C function system(), and has the same limitations.
    Changes to sys.stdin, etc. are not reflected in the environment of
    the executed command. If command generates any output, it will be sent to
    the interpreter standard output stream.

    On Unix, the return value is the exit status of the process encoded in the
    format specified for wait(). Note that POSIX does not specify the
    meaning of the return value of the C system() function, so the return
    value of the Python function is system-dependent.

    On Windows, the return value is that returned by the system shell after
    running command. The shell is given by the Windows environment variable
    COMSPEC: it is usually cmd.exe, which returns the exit
    status of the command run; on systems using a non-native shell, consult your
    shell documentation.

    The subprocess module provides more powerful facilities for spawning
    new processes and retrieving their results; using that module is preferable
    to using this function. See the Replacing Older Functions with the subprocess Module section in
    the subprocess documentation for some helpful recipes.

    Availability: Unix, Windows.

    os.times()

    Returns the current global process times.
    The return value is an object with five attributes:

    • user — user time
    • system — system time
    • children_user — user time of all child processes
    • children_system — system time of all child processes
    • elapsed — elapsed real time since a fixed point in the past

    For backwards compatibility, this object also behaves like a five-tuple
    containing user, system, children_user,
    children_system, and elapsed in that order.

    See the Unix manual page
    times(2) or the corresponding Windows Platform API documentation.
    On Windows, only user and system are known; the other
    attributes are zero.

    Availability: Unix, Windows.

    Changed in version 3.3: Return type changed from a tuple to a tuple-like object
    with named attributes.

    os.wait()

    Wait for completion of a child process, and return a tuple containing its pid
    and exit status indication: a 16-bit number, whose low byte is the signal number
    that killed the process, and whose high byte is the exit status (if the signal
    number is zero); the high bit of the low byte is set if a core file was
    produced.

    Availability: Unix.

    os.waitid(idtype, id, options)

    Wait for the completion of one or more child processes.
    idtype can be P_PID, P_PGID or P_ALL.
    id specifies the pid to wait on.
    options is constructed from the ORing of one or more of WEXITED,
    WSTOPPED or WCONTINUED and additionally may be ORed with
    WNOHANG or WNOWAIT. The return value is an object
    representing the data contained in the siginfo_t structure, namely:
    si_pid, si_uid, si_signo, si_status,
    si_code or None if WNOHANG is specified and there are no
    children in a waitable state.

    Availability: Unix.

    New in version 3.3.

    os.P_PID
    os.P_PGID
    os.P_ALL

    These are the possible values for idtype in waitid(). They affect
    how id is interpreted.

    Availability: Unix.

    New in version 3.3.

    os.WEXITED
    os.WSTOPPED
    os.WNOWAIT

    Flags that can be used in options in waitid() that specify what
    child signal to wait for.

    Availability: Unix.

    New in version 3.3.

    os.CLD_EXITED
    os.CLD_DUMPED
    os.CLD_TRAPPED
    os.CLD_CONTINUED

    These are the possible values for si_code in the result returned by
    waitid().

    Availability: Unix.

    New in version 3.3.

    os.waitpid(pid, options)

    The details of this function differ on Unix and Windows.

    On Unix: Wait for completion of a child process given by process id pid, and
    return a tuple containing its process id and exit status indication (encoded as
    for wait()). The semantics of the call are affected by the value of the
    integer options, which should be 0 for normal operation.

    If pid is greater than 0, waitpid() requests status information for
    that specific process. If pid is 0, the request is for the status of any
    child in the process group of the current process. If pid is -1, the
    request pertains to any child of the current process. If pid is less than
    -1, status is requested for any process in the process group -pid (the
    absolute value of pid).

    An OSError is raised with the value of errno when the syscall
    returns -1.

    On Windows: Wait for completion of a process given by process handle pid, and
    return a tuple containing pid, and its exit status shifted left by 8 bits
    (shifting makes cross-platform use of the function easier). A pid less than or
    equal to 0 has no special meaning on Windows, and raises an exception. The
    value of integer options has no effect. pid can refer to any process whose
    id is known, not necessarily a child process. The spawn*
    functions called with P_NOWAIT return suitable process handles.

    Changed in version 3.5: If the system call is interrupted and the signal handler does not raise an
    exception, the function now retries the system call instead of raising an
    InterruptedError exception (see PEP 475 for the rationale).

    os.wait3(options)

    Similar to waitpid(), except no process id argument is given and a
    3-element tuple containing the child’s process id, exit status indication, and
    resource usage information is returned. Refer to resource.getrusage() for details on resource usage information. The
    option argument is the same as that provided to waitpid() and
    wait4().

    Availability: Unix.

    os.wait4(pid, options)

    Similar to waitpid(), except a 3-element tuple, containing the child’s
    process id, exit status indication, and resource usage information is returned.
    Refer to resource.getrusage() for details on
    resource usage information. The arguments to wait4() are the same
    as those provided to waitpid().

    Availability: Unix.

    os.WNOHANG

    The option for waitpid() to return immediately if no child process status
    is available immediately. The function returns (0, 0) in this case.

    Availability: Unix.

    os.WCONTINUED

    This option causes child processes to be reported if they have been continued
    from a job control stop since their status was last reported.

    Availability: some Unix systems.

    os.WUNTRACED

    This option causes child processes to be reported if they have been stopped but
    their current state has not been reported since they were stopped.

    Availability: Unix.

    The following functions take a process status code as returned by
    system(), wait(), or waitpid() as a parameter. They may be
    used to determine the disposition of a process.

    os.WCOREDUMP(status)

    Return True if a core dump was generated for the process, otherwise
    return False.

    Availability: Unix.

    os.WIFCONTINUED(status)

    Return True if the process has been continued from a job control stop,
    otherwise return False.

    Availability: Unix.

    os.WIFSTOPPED(status)

    Return True if the process has been stopped, otherwise return
    False.

    Availability: Unix.

    os.WIFSIGNALED(status)

    Return True if the process exited due to a signal, otherwise return
    False.

    Availability: Unix.

    os.WIFEXITED(status)

    Return True if the process exited using the exit(2) system call,
    otherwise return False.

    Availability: Unix.

    os.WEXITSTATUS(status)

    If WIFEXITED(status) is true, return the integer parameter to the
    exit(2) system call. Otherwise, the return value is meaningless.

    Availability: Unix.

    os.WSTOPSIG(status)

    Return the signal which caused the process to stop.

    Availability: Unix.

    os.WTERMSIG(status)

    Return the signal which caused the process to exit.

    Availability: Unix.

    16.1.7. Interface to the scheduler¶

    These functions control how a process is allocated CPU time by the operating
    system. They are only available on some Unix platforms. For more detailed
    information, consult your Unix manpages.

    New in version 3.3.

    The following scheduling policies are exposed if they are supported by the
    operating system.

    os.SCHED_OTHER

    The default scheduling policy.

    os.SCHED_BATCH

    Scheduling policy for CPU-intensive processes that tries to preserve
    interactivity on the rest of the computer.

    os.SCHED_IDLE

    Scheduling policy for extremely low priority background tasks.

    os.SCHED_SPORADIC

    Scheduling policy for sporadic server programs.

    os.SCHED_FIFO

    A First In First Out scheduling policy.

    os.SCHED_RR

    A round-robin scheduling policy.

    os.SCHED_RESET_ON_FORK

    This flag can be OR’ed with any other scheduling policy. When a process with
    this flag set forks, its child’s scheduling policy and priority are reset to
    the default.

    class os.sched_param(sched_priority)

    This class represents tunable scheduling parameters used in
    sched_setparam(), sched_setscheduler(), and
    sched_getparam(). It is immutable.

    At the moment, there is only one possible parameter:

    sched_priority

    The scheduling priority for a scheduling policy.

    os.sched_get_priority_min(policy)

    Get the minimum priority value for policy. policy is one of the
    scheduling policy constants above.

    os.sched_get_priority_max(policy)

    Get the maximum priority value for policy. policy is one of the
    scheduling policy constants above.

    os.sched_setscheduler(pid, policy, param)

    Set the scheduling policy for the process with PID pid. A pid of 0 means
    the calling process. policy is one of the scheduling policy constants
    above. param is a sched_param instance.

    os.sched_getscheduler(pid)

    Return the scheduling policy for the process with PID pid. A pid of 0
    means the calling process. The result is one of the scheduling policy
    constants above.

    os.sched_setparam(pid, param)

    Set a scheduling parameters for the process with PID pid. A pid of 0 means
    the calling process. param is a sched_param instance.

    os.sched_getparam(pid)

    Return the scheduling parameters as a sched_param instance for the
    process with PID pid. A pid of 0 means the calling process.

    os.sched_rr_get_interval(pid)

    Return the round-robin quantum in seconds for the process with PID pid. A
    pid of 0 means the calling process.

    os.sched_yield()

    Voluntarily relinquish the CPU.

    os.sched_setaffinity(pid, mask)

    Restrict the process with PID pid (or the current process if zero) to a
    set of CPUs. mask is an iterable of integers representing the set of
    CPUs to which the process should be restricted.

    os.sched_getaffinity(pid)

    Return the set of CPUs the process with PID pid (or the current process
    if zero) is restricted to.

    16.1.8. Miscellaneous System Information¶

    os.confstr(name)

    Return string-valued system configuration values. name specifies the
    configuration value to retrieve; it may be a string which is the name of a
    defined system value; these names are specified in a number of standards (POSIX,
    Unix 95, Unix 98, and others). Some platforms define additional names as well.
    The names known to the host operating system are given as the keys of the
    confstr_names dictionary. For configuration variables not included in that
    mapping, passing an integer for name is also accepted.

    If the configuration value specified by name isn’t defined, None is
    returned.

    If name is a string and is not known, ValueError is raised. If a
    specific value for name is not supported by the host system, even if it is
    included in confstr_names, an OSError is raised with
    errno.EINVAL for the error number.

    Availability: Unix.

    os.confstr_names

    Dictionary mapping names accepted by confstr() to the integer values
    defined for those names by the host operating system. This can be used to
    determine the set of names known to the system.

    Availability: Unix.

    os.cpu_count()

    Return the number of CPUs in the system. Returns None if undetermined.

    This number is not equivalent to the number of CPUs the current process can
    use. The number of usable CPUs can be obtained with
    len(os.sched_getaffinity(0))

    New in version 3.4.

    os.getloadavg()

    Return the number of processes in the system run queue averaged over the last
    1, 5, and 15 minutes or raises OSError if the load average was
    unobtainable.

    Availability: Unix.

    os.sysconf(name)

    Return integer-valued system configuration values. If the configuration value
    specified by name isn’t defined, -1 is returned. The comments regarding
    the name parameter for confstr() apply here as well; the dictionary that
    provides information on the known names is given by sysconf_names.

    Availability: Unix.

    os.sysconf_names

    Dictionary mapping names accepted by sysconf() to the integer values
    defined for those names by the host operating system. This can be used to
    determine the set of names known to the system.

    Availability: Unix.

    The following data values are used to support path manipulation operations. These
    are defined for all platforms.

    Higher-level operations on pathnames are defined in the os.path module.

    os.curdir

    The constant string used by the operating system to refer to the current
    directory. This is '.' for Windows and POSIX. Also available via
    os.path.

    os.pardir

    The constant string used by the operating system to refer to the parent
    directory. This is '..' for Windows and POSIX. Also available via
    os.path.

    os.sep

    The character used by the operating system to separate pathname components.
    This is '/' for POSIX and '\' for Windows. Note that knowing this
    is not sufficient to be able to parse or concatenate pathnames — use
    os.path.split() and os.path.join() — but it is occasionally
    useful. Also available via os.path.

    os.altsep

    An alternative character used by the operating system to separate pathname
    components, or None if only one separator character exists. This is set to
    '/' on Windows systems where sep is a backslash. Also available via
    os.path.

    os.extsep

    The character which separates the base filename from the extension; for example,
    the '.' in os.py. Also available via os.path.

    os.pathsep

    The character conventionally used by the operating system to separate search
    path components (as in PATH), such as ':' for POSIX or ';' for
    Windows. Also available via os.path.

    os.defpath

    The default search path used by exec*p* and
    spawn*p* if the environment doesn’t have a 'PATH'
    key. Also available via os.path.

    os.linesep

    The string used to separate (or, rather, terminate) lines on the current
    platform. This may be a single character, such as 'n' for POSIX, or
    multiple characters, for example, 'rn' for Windows. Do not use
    os.linesep as a line terminator when writing files opened in text mode (the
    default); use a single 'n' instead, on all platforms.

    os.devnull

    The file path of the null device. For example: '/dev/null' for
    POSIX, 'nul' for Windows. Also available via os.path.

    os.RTLD_LAZY
    os.RTLD_NOW
    os.RTLD_GLOBAL
    os.RTLD_LOCAL
    os.RTLD_NODELETE
    os.RTLD_NOLOAD
    os.RTLD_DEEPBIND

    Flags for use with the setdlopenflags() and
    getdlopenflags() functions. See the Unix manual page
    dlopen(3) for what the different flags mean.

    New in version 3.3.

    16.1.9. Random numbers¶

    os.getrandom(size, flags=0)

    Get up to size random bytes. The function can return less bytes than
    requested.

    These bytes can be used to seed user-space random number generators or for
    cryptographic purposes.

    getrandom() relies on entropy gathered from device drivers and other
    sources of environmental noise. Unnecessarily reading large quantities of
    data will have a negative impact on other users of the /dev/random and
    /dev/urandom devices.

    The flags argument is a bit mask that can contain zero or more of the
    following values ORed together: os.GRND_RANDOM and
    GRND_NONBLOCK.

    See also the Linux getrandom() manual page.

    Availability: Linux 3.17 and newer.

    New in version 3.6.

    os.urandom(size)

    Return a string of size random bytes suitable for cryptographic use.

    This function returns random bytes from an OS-specific randomness source. The
    returned data should be unpredictable enough for cryptographic applications,
    though its exact quality depends on the OS implementation.

    On Linux, if the getrandom() syscall is available, it is used in
    blocking mode: block until the system urandom entropy pool is initialized
    (128 bits of entropy are collected by the kernel). See the PEP 524 for
    the rationale. On Linux, the getrandom() function can be used to get
    random bytes in non-blocking mode (using the GRND_NONBLOCK flag) or
    to poll until the system urandom entropy pool is initialized.

    On a Unix-like system, random bytes are read from the /dev/urandom
    device. If the /dev/urandom device is not available or not readable, the
    NotImplementedError exception is raised.

    On Windows, it will use CryptGenRandom().

    See also

    The secrets module provides higher level functions. For an
    easy-to-use interface to the random number generator provided by your
    platform, please see random.SystemRandom.

    Changed in version 3.6.0: On Linux, getrandom() is now used in blocking mode to increase the
    security.

    Changed in version 3.5.2: On Linux, if the getrandom() syscall blocks (the urandom entropy pool
    is not initialized yet), fall back on reading /dev/urandom.

    Changed in version 3.5: On Linux 3.17 and newer, the getrandom() syscall is now used
    when available. On OpenBSD 5.6 and newer, the C getentropy()
    function is now used. These functions avoid the usage of an internal file
    descriptor.

    os.GRND_NONBLOCK

    By default, when reading from /dev/random, getrandom() blocks if
    no random bytes are available, and when reading from /dev/urandom, it blocks
    if the entropy pool has not yet been initialized.

    If the GRND_NONBLOCK flag is set, then getrandom() does not
    block in these cases, but instead immediately raises BlockingIOError.

    New in version 3.6.

    os.GRND_RANDOM

    If this bit is set, then random bytes are drawn from the
    /dev/random pool instead of the /dev/urandom pool.

    New in version 3.6.

    1. Reference
    2. Python Functions
    3. Python os.kill() Method
    1. Syntax of the os.kill() Method
    2. Example Codes: Working With the os.kill() Method in Python
    3. Example Codes: Understanding the os.kill() Method in Python

    Python os.kill() Method

    Python os.kill() method is an efficient way of killing or terminating a process using its process identifier (pid).

    Syntax of the os.kill() Method

    Parameters

    pid It is an integer representing an ID of the process we are addressing.
    signal It is an integer representing a signal number needed to send to the process.

    Return

    In the execution process, this method does not return any value.

    Example Codes: Working With the os.kill() Method in Python

    import os, signal
    
    pID = os.fork()
    
    if pID :
        print("---PARENT PROCESS---")
    
        os.kill(pID, signal.SIGSTOP)
    
        print("The parent process has been killed.")
    
        os.kill(pID, signal.SIGCONT)
    
    else :
    
        print("Hello, World!")
    

    Output:

    ---PARENT PROCESS---
    The parent process has been killed.
    Hello, World!
    

    Python offers different signal modules. In the above code, variables signal.SIGSTOP are used to stop the current process.

    Another variable, signal.SIGCONT, is used, which continues the current process.

    Example Codes: Understanding the os.kill() Method in Python

    import os
    
    import signal
    
    def process():
        print ("The process ID:", os.getpid())
    
        os.kill(os.getpid(), signal.SIGKILL)
    
    process()
    

    Output:

    Every time we run the above code, a new process executes; thus, different process IDs are obtained. In the above code, the variable signal.SIGKILL is used to kill the current process.

    Musfirah Waseem avatar
    Musfirah Waseem avatar

    Musfirah is a student of computer science from the best university in Pakistan. She has a knack for programming and everything related. She is a tech geek who loves to help people as much as possible.

    LinkedIn

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  • July 4, 2020May 26, 2021

    When automating some tasks in Windows OS, you may wonder how to automatically close Windows process if you do not have the direct control of the running application or when the application is just running for too long time. In this article, I will be sharing with you how to close the Windows process with some python library, to be more specific, the pywin32 library.

    Prerequisites

    You will need to install the pywin32 library if you have not yet installed:

    Find the process name from Windows Task Manager

    You will need to first find out the application name which you intend to close, the application name can be found from the Windows task manager. E.g. If you expand the “Windows Command Processor” process, you can see the running process is “cmd.exe”.

    python close Windows process

    Let’s get started with the code!

    Import the below modules that we will be using later:

    from win32com.client import GetObject
    from datetime import datetime
    
    import os

    And we need to get the WMI (Windows Management Instrumentation) service via the below code, where we can further access the window processes. For more information about WMI, please check this.

    WMI = GetObject('winmgmts:')

    Next, we will use the WMI SQL query to get the processes from the Win32_Process table by passing in the application name. Remember we have already found the application name earlier from the task manager.

    for p in WMI.ExecQuery('select * from Win32_Process where Name="cmd.exe"'):
        #the date format is something like this 20200613144903.166769+480
        create_dt, *_ = p.CreationDate.split('.')
        diff = datetime.now() - datetime.strptime(create_dt,'%Y%m%d%H%M%S')
    
    

    There are other properties such as Description, Status, Executable Path, etc. You can check the full list of the process properties from this win32-process documentation. Here we want to base on the creation date to calculate how much time the application has been running to determine if we want to kill it.

    Assuming we need to close windows process after it is running for 5 minutes.

        if diff.seconds/60 > 5:		
            print("Terminating PID:", p.ProcessId)
    	os.system("taskkill /pid "+str(p.ProcessId))

    With this taskkill command, we will be able to terminate all the threads under this Windows process peacefully.

    Conclusion

    The pywin32 is super powerful python library especially when dealing with the Windows applications. You can use it to read & save attachments from outlook, send emails via outlook , open excel files and some more. Do have a check on these articles.

    As per always, welcome any comments or questions.

    Post tagspythonpywin32Win32_Process

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    Sometimes you need to kill processes running on your machine, for example to clean up after an application has hung, or when you want to wipe out some background tasks in a hurry. Killing processes, particularly on Windows, can be a bit of a manual process. There are command line programs like taskill.exe, but it’s useful to be able to combine process killing with a programming language like Python which lets you easily add pattern matching to selectively pick the processes.

    Let’s go through the steps of listing, matching, and killing processes running on the machine.

     
    How to list processes
     

    The first step is to list the processes that are running. This can be accomplished using the psutil Python library – a cross-platform library for process and system monitoring.

    '''list running processes'''
    import psutil
    
    for proc in psutil.process_iter():
        print(proc.name())
    

    When you run this code on Windows, the list of process names will not always match the display names listed in Task Manager. You can see the process names in Task Manager when you right-click and select properties. This is important when it comes to matching strings to kill a process, and why listing the processes first is useful.

    How to kill a process

    Once you have selected a process the command to kill it using psutil looks like this:

       proc.kill()
    

    However, if you didn’t create the process in the first place, or it wasn’t created on your behalf, you won’t have permission to kill it, unless you’re running the code as “Administrator” or “superuser”. For example on Windows you could start a PowerShell window by right-clicking and selecting “Run as Administrator”, or on Linux run using sudo.

     
    How to kill processes based on partial strings

    In this example, a friend of mine who spends too much time gaming wants to run a game that is highly demanding of CPU and memory, so they want to kill the Adobe Creative Cloud processes that are running and don’t currently need, (but also want to leave it all installed so they can use the video editing when they need it).

    After checking the process list, the process names to kill contain the strings: “Adobe”, “CCXProcess”, “CoreSync” and “Creative Cloud”. You could match the strings with a set of “or” statements, but another way to match a name from a list of strings in Python is to use the built-in function: any.

    A simple Python 3 program to match and kill processes looks like this:

    '''pykill.py - selective process kill prog'''
    import psutil
    
    
    def main():
        '''Process kill function'''    
        for proc in psutil.process_iter():
            # check whether the process name matches
            # print(proc.name())
            if any(procstr in proc.name() for procstr in
                ['Adobe', 'CCXProcess', 'CoreSync', 'Creative Cloud']):
                print(f'Killing {proc.name()}')
                proc.kill()
    
    
    if __name__ == "__main__":
        main()
    

    Before running your own version of this and breaking your OS, it’s a good idea to test it. E.g. start something like notepad and replace the string list with [‘notepad’]. You wouldn’t need to run a notepad killer as Administrator (unless other people are also logged in and you wanted to kill their notepads).

    Python kills the Windows process

    tags: LQ-Other  python  windows  Operation and maintenance

    1 Batch kill the same process:

    CMD = 'Taskkill / F / IM' + Process Name
    os.system(cmd)
    

    2 Kill a process by PID:

    CMD = 'taskkill / f / pid' + PID value
    os.system(cmd)
    

    1 Query all PIDs:

    list_process = list()
    pid_list = psutil.pids()
    for sub_pid in pid_list:
        try:
            process_info = psutil.Process(sub_pid)
            IF process name == Process_info.name ():
                list_process.append(sub_pid)
        except (psutil.NoSuchProcess, psutil.AccessDenied, psutil.ZombieProcess):
            pass
    

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