cpython/Lib/subprocess.py at 3.14 · python/cpython · GitHub

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# subprocess - Subprocesses with accessible I/O streams

# For more information about this module, see PEP 324.

# Licensed to PSF under a Contributor Agreement.

r"""Subprocesses with accessible I/O streams

This module allows you to spawn processes, connect to their

input/output/error pipes, and obtain their return codes.

For a complete description of this module see the Python documentation.

Main API

========

run(...): Runs a command, waits for it to complete, then returns a

CompletedProcess instance.

Popen(...): A class for flexibly executing a command in a new process

Constants

---------

DEVNULL: Special value that indicates that os.devnull should be used

PIPE: Special value that indicates a pipe should be created

STDOUT: Special value that indicates that stderr should go to stdout

Older API

=========

call(...): Runs a command, waits for it to complete, then returns

the return code.

check_call(...): Same as call() but raises CalledProcessError()

if return code is not 0

check_output(...): Same as check_call() but returns the contents of

stdout instead of a return code

getoutput(...): Runs a command in the shell, waits for it to complete,

then returns the output

getstatusoutput(...): Runs a command in the shell, waits for it to complete,

then returns a (exitcode, output) tuple

"""

import builtins

import errno

import io

import locale

import os

import time

import signal

import sys

import threading

import warnings

import contextlib

from time import monotonic as _time

import types

try:

import fcntl

except ImportError:

fcntl = None

__all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput",

"getoutput", "check_output", "run", "CalledProcessError", "DEVNULL",

"SubprocessError", "TimeoutExpired", "CompletedProcess"]

# NOTE: We intentionally exclude list2cmdline as it is

# considered an internal implementation detail. issue10838.

# use presence of msvcrt to detect Windows-like platforms (see bpo-8110)

try:

import msvcrt

except ModuleNotFoundError:

_mswindows = False

else:

_mswindows = True

# some platforms do not support subprocesses

_can_fork_exec = sys.platform not in {"emscripten", "wasi", "ios", "tvos", "watchos"}

if _mswindows:

import _winapi

from _winapi import (CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP, # noqa: F401

STD_INPUT_HANDLE, STD_OUTPUT_HANDLE,

STD_ERROR_HANDLE, SW_HIDE,

STARTF_USESTDHANDLES, STARTF_USESHOWWINDOW,

STARTF_FORCEONFEEDBACK, STARTF_FORCEOFFFEEDBACK,

ABOVE_NORMAL_PRIORITY_CLASS, BELOW_NORMAL_PRIORITY_CLASS,

HIGH_PRIORITY_CLASS, IDLE_PRIORITY_CLASS,

NORMAL_PRIORITY_CLASS, REALTIME_PRIORITY_CLASS,

CREATE_NO_WINDOW, DETACHED_PROCESS,

CREATE_DEFAULT_ERROR_MODE, CREATE_BREAKAWAY_FROM_JOB)

__all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP",

"STD_INPUT_HANDLE", "STD_OUTPUT_HANDLE",

"STD_ERROR_HANDLE", "SW_HIDE",

"STARTF_USESTDHANDLES", "STARTF_USESHOWWINDOW",

"STARTF_FORCEONFEEDBACK", "STARTF_FORCEOFFFEEDBACK",

"STARTUPINFO",

"ABOVE_NORMAL_PRIORITY_CLASS", "BELOW_NORMAL_PRIORITY_CLASS",

"HIGH_PRIORITY_CLASS", "IDLE_PRIORITY_CLASS",

"NORMAL_PRIORITY_CLASS", "REALTIME_PRIORITY_CLASS",

"CREATE_NO_WINDOW", "DETACHED_PROCESS",

"CREATE_DEFAULT_ERROR_MODE", "CREATE_BREAKAWAY_FROM_JOB"])

else:

if _can_fork_exec:

from _posixsubprocess import fork_exec as _fork_exec

# used in methods that are called by __del__

class _del_safe:

waitpid = os.waitpid

waitstatus_to_exitcode = os.waitstatus_to_exitcode

WIFSTOPPED = os.WIFSTOPPED

WSTOPSIG = os.WSTOPSIG

WNOHANG = os.WNOHANG

ECHILD = errno.ECHILD

else:

class _del_safe:

waitpid = None

waitstatus_to_exitcode = None

WIFSTOPPED = None

WSTOPSIG = None

WNOHANG = None

ECHILD = errno.ECHILD

import select

import selectors

# Exception classes used by this module.

class SubprocessError(Exception): pass

class CalledProcessError(SubprocessError):

"""Raised when run() is called with check=True and the process

returns a non-zero exit status.

Attributes:

cmd, returncode, stdout, stderr, output

"""

def __init__(self, returncode, cmd, output=None, stderr=None):

self.returncode = returncode

self.cmd = cmd

self.output = output

self.stderr = stderr

def __str__(self):

if isinstance(self.returncode, int) and self.returncode < 0:

try:

return "Command '%s' died with %r." % (

self.cmd, signal.Signals(-self.returncode))

except ValueError:

return "Command '%s' died with unknown signal %d." % (

self.cmd, -self.returncode)

else:

return (f"Command '{self.cmd}' returned non-zero "

f"exit status {self.returncode}.")

@property

def stdout(self):

"""Alias for output attribute, to match stderr"""

return self.output

@stdout.setter

def stdout(self, value):

# There's no obvious reason to set this, but allow it anyway so

# .stdout is a transparent alias for .output

self.output = value

class TimeoutExpired(SubprocessError):

"""This exception is raised when the timeout expires while waiting for a

child process.

Attributes:

cmd, output, stdout, stderr, timeout

"""

def __init__(self, cmd, timeout, output=None, stderr=None):

self.cmd = cmd

self.timeout = timeout

self.output = output

self.stderr = stderr

def __str__(self):

return ("Command '%s' timed out after %s seconds" %

(self.cmd, self.timeout))

@property

def stdout(self):

return self.output

@stdout.setter

def stdout(self, value):

# There's no obvious reason to set this, but allow it anyway so

# .stdout is a transparent alias for .output

self.output = value

if _mswindows:

class STARTUPINFO:

def __init__(self, *, dwFlags=0, hStdInput=None, hStdOutput=None,

hStdError=None, wShowWindow=0, lpAttributeList=None):

self.dwFlags = dwFlags

self.hStdInput = hStdInput

self.hStdOutput = hStdOutput

self.hStdError = hStdError

self.wShowWindow = wShowWindow

self.lpAttributeList = lpAttributeList or {"handle_list": []}

def copy(self):

attr_list = self.lpAttributeList.copy()

if 'handle_list' in attr_list:

attr_list['handle_list'] = list(attr_list['handle_list'])

return STARTUPINFO(dwFlags=self.dwFlags,

hStdInput=self.hStdInput,

hStdOutput=self.hStdOutput,

hStdError=self.hStdError,

wShowWindow=self.wShowWindow,

lpAttributeList=attr_list)

class Handle(int):

closed = False

def Close(self, CloseHandle=_winapi.CloseHandle):

if not self.closed:

self.closed = True

CloseHandle(self)

def Detach(self):

if not self.closed:

self.closed = True

return int(self)

raise ValueError("already closed")

def __repr__(self):

return "%s(%d)" % (self.__class__.__name__, int(self))

__del__ = Close

else:

# When select or poll has indicated that the file is writable,

# we can write up to _PIPE_BUF bytes without risk of blocking.

# POSIX defines PIPE_BUF as >= 512.

_PIPE_BUF = getattr(select, 'PIPE_BUF', 512)

# poll/select have the advantage of not requiring any extra file

# descriptor, contrarily to epoll/kqueue (also, they require a single

# syscall).

if hasattr(selectors, 'PollSelector'):

_PopenSelector = selectors.PollSelector

else:

_PopenSelector = selectors.SelectSelector

if _mswindows:

# On Windows we just need to close `Popen._handle` when we no longer need

# it, so that the kernel can free it. `Popen._handle` gets closed

# implicitly when the `Popen` instance is finalized (see `Handle.__del__`,

# which is calling `CloseHandle` as requested in [1]), so there is nothing

# for `_cleanup` to do.

# [1] https://docs.microsoft.com/en-us/windows/desktop/ProcThread/

# creating-processes

_active = None

def _cleanup():

pass

else:

# This lists holds Popen instances for which the underlying process had not

# exited at the time its __del__ method got called: those processes are

# wait()ed for synchronously from _cleanup() when a new Popen object is

# created, to avoid zombie processes.

_active = []

def _cleanup():

if _active is None:

return

for inst in _active[:]:

res = inst._internal_poll(_deadstate=sys.maxsize)

if res is not None:

try:

_active.remove(inst)

except ValueError:

# This can happen if two threads create a new Popen instance.

# It's harmless that it was already removed, so ignore.

pass

PIPE = -1

STDOUT = -2

DEVNULL = -3

# XXX This function is only used by multiprocessing and the test suite,

# but it's here so that it can be imported when Python is compiled without

# threads.

def _optim_args_from_interpreter_flags():

"""Return a list of command-line arguments reproducing the current

optimization settings in sys.flags."""

args = []

value = sys.flags.optimize

if value > 0:

args.append('-' + 'O' * value)

return args

def _args_from_interpreter_flags():

"""Return a list of command-line arguments reproducing the current

settings in sys.flags, sys.warnoptions and sys._xoptions."""

flag_opt_map = {

'debug': 'd',

# 'inspect': 'i',

# 'interactive': 'i',

'dont_write_bytecode': 'B',

'no_site': 'S',

'verbose': 'v',

'bytes_warning': 'b',

'quiet': 'q',

# -O is handled in _optim_args_from_interpreter_flags()

}

args = _optim_args_from_interpreter_flags()

for flag, opt in flag_opt_map.items():

v = getattr(sys.flags, flag)

if v > 0:

args.append('-' + opt * v)

if sys.flags.isolated:

args.append('-I')

else:

if sys.flags.ignore_environment:

args.append('-E')

if sys.flags.no_user_site:

args.append('-s')

if sys.flags.safe_path:

args.append('-P')

# -W options

warnopts = sys.warnoptions[:]

xoptions = getattr(sys, '_xoptions', {})

bytes_warning = sys.flags.bytes_warning

dev_mode = sys.flags.dev_mode

if bytes_warning > 1:

warnopts.remove("error::BytesWarning")

elif bytes_warning:

warnopts.remove("default::BytesWarning")

if dev_mode:

warnopts.remove('default')

for opt in warnopts:

args.append('-W' + opt)

# -X options

if dev_mode:

args.extend(('-X', 'dev'))

for opt in sorted(xoptions):

if opt == 'dev':

# handled above via sys.flags.dev_mode

continue

value = xoptions[opt]

if value is True:

arg = opt

else:

arg = '%s=%s' % (opt, value)

args.extend(('-X', arg))

return args

def _text_encoding():

# Return default text encoding and emit EncodingWarning if

# sys.flags.warn_default_encoding is true.

if sys.flags.warn_default_encoding:

f = sys._getframe()

filename = f.f_code.co_filename

stacklevel = 2

while f := f.f_back:

if f.f_code.co_filename != filename:

break

stacklevel += 1

warnings.warn("'encoding' argument not specified.",

EncodingWarning, stacklevel)

if sys.flags.utf8_mode:

return "utf-8"

else:

return locale.getencoding()

def call(*popenargs, timeout=None, **kwargs):

"""Run command with arguments. Wait for command to complete or

for timeout seconds, then return the returncode attribute.

The arguments are the same as for the Popen constructor. Example:

retcode = call(["ls", "-l"])

"""

with Popen(*popenargs, **kwargs) as p:

try:

return p.wait(timeout=timeout)

except: # Including KeyboardInterrupt, wait handled that.

p.kill()

# We don't call p.wait() again as p.__exit__ does that for us.

raise

def check_call(*popenargs, **kwargs):

"""Run command with arguments. Wait for command to complete. If

the exit code was zero then return, otherwise raise

CalledProcessError. The CalledProcessError object will have the

return code in the returncode attribute.

The arguments are the same as for the call function. Example:

check_call(["ls", "-l"])

"""

retcode = call(*popenargs, **kwargs)

if retcode:

cmd = kwargs.get("args")

if cmd is None:

cmd = popenargs[0]

raise CalledProcessError(retcode, cmd)

return 0

def check_output(*popenargs, timeout=None, **kwargs):

r"""Run command with arguments and return its output.

If the exit code was non-zero it raises a CalledProcessError. The

CalledProcessError object will have the return code in the returncode

attribute and output in the output attribute.

The arguments are the same as for the Popen constructor. Example:

>>> check_output(["ls", "-l", "/dev/null"])

b'crw-rw-rw- 1 root root 1, 3 Oct 18 2007 /dev/null\n'

The stdout argument is not allowed as it is used internally.

To capture standard error in the result, use stderr=STDOUT.

>>> check_output(["/bin/sh", "-c",

... "ls -l non_existent_file ; exit 0"],

... stderr=STDOUT)

b'ls: non_existent_file: No such file or directory\n'

There is an additional optional argument, "input", allowing you to

pass a string to the subprocess's stdin. If you use this argument

you may not also use the Popen constructor's "stdin" argument, as

it too will be used internally. Example:

>>> check_output(["sed", "-e", "s/foo/bar/"],

... input=b"when in the course of fooman events\n")

b'when in the course of barman events\n'

By default, all communication is in bytes, and therefore any "input"

should be bytes, and the return value will be bytes. If in text mode,

any "input" should be a string, and the return value will be a string

decoded according to locale encoding, or by "encoding" if set. Text mode

is triggered by setting any of text, encoding, errors or universal_newlines.

"""

for kw in ('stdout', 'check'):

if kw in kwargs:

raise ValueError(f'{kw} argument not allowed, it will be overridden.')

if 'input' in kwargs and kwargs['input'] is None:

# Explicitly passing input=None was previously equivalent to passing an

# empty string. That is maintained here for backwards compatibility.

if kwargs.get('universal_newlines') or kwargs.get('text') or kwargs.get('encoding') \

or kwargs.get('errors'):

empty = ''

else:

empty = b''

kwargs['input'] = empty

return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,

**kwargs).stdout

class CompletedProcess(object):

"""A process that has finished running.

This is returned by run().

Attributes:

args: The list or str args passed to run().

returncode: The exit code of the process, negative for signals.

stdout: The standard output (None if not captured).

stderr: The standard error (None if not captured).

"""

def __init__(self, args, returncode, stdout=None, stderr=None):

self.args = args

self.returncode = returncode

self.stdout = stdout

self.stderr = stderr

def __repr__(self):

args = ['args={!r}'.format(self.args),

'returncode={!r}'.format(self.returncode)]

if self.stdout is not None:

args.append('stdout={!r}'.format(self.stdout))

if self.stderr is not None:

args.append('stderr={!r}'.format(self.stderr))

return "{}({})".format(type(self).__name__, ', '.join(args))

__class_getitem__ = classmethod(types.GenericAlias)

def check_returncode(self):

"""Raise CalledProcessError if the exit code is non-zero."""

if self.returncode:

raise CalledProcessError(self.returncode, self.args, self.stdout,

self.stderr)

def run(*popenargs,

input=None, capture_output=False, timeout=None, check=False, **kwargs):

"""Run command with arguments and return a CompletedProcess instance.

The returned instance will have attributes args, returncode, stdout and

stderr. By default, stdout and stderr are not captured, and those attributes

will be None. Pass stdout=PIPE and/or stderr=PIPE in order to capture them,

or pass capture_output=True to capture both.

If check is True and the exit code was non-zero, it raises a

CalledProcessError. The CalledProcessError object will have the return code

in the returncode attribute, and output & stderr attributes if those streams

were captured.

If timeout (seconds) is given and the process takes too long,

a TimeoutExpired exception will be raised.

There is an optional argument "input", allowing you to

pass bytes or a string to the subprocess's stdin. If you use this argument

you may not also use the Popen constructor's "stdin" argument, as

it will be used internally.

By default, all communication is in bytes, and therefore any "input" should

be bytes, and the stdout and stderr will be bytes. If in text mode, any

"input" should be a string, and stdout and stderr will be strings decoded

according to locale encoding, or by "encoding" if set. Text mode is

triggered by setting any of text, encoding, errors or universal_newlines.

The other arguments are the same as for the Popen constructor.

"""

if input is not None:

if kwargs.get('stdin') is not None:

raise ValueError('stdin and input arguments may not both be used.')

kwargs['stdin'] = PIPE

if capture_output:

if kwargs.get('stdout') is not None or kwargs.get('stderr') is not None:

raise ValueError('stdout and stderr arguments may not be used '

'with capture_output.')

kwargs['stdout'] = PIPE

kwargs['stderr'] = PIPE

with Popen(*popenargs, **kwargs) as process:

try:

stdout, stderr = process.communicate(input, timeout=timeout)

except TimeoutExpired as exc:

process.kill()

if _mswindows:

# Windows accumulates the output in a single blocking

# read() call run on child threads, with the timeout

# being done in a join() on those threads. communicate()

# _after_ kill() is required to collect that and add it

# to the exception.

exc.stdout, exc.stderr = process.communicate()

else:

# POSIX _communicate already populated the output so

# far into the TimeoutExpired exception.

process.wait()

raise

except: # Including KeyboardInterrupt, communicate handled that.

process.kill()

# We don't call process.wait() as .__exit__ does that for us.

raise

retcode = process.poll()

if check and retcode:

raise CalledProcessError(retcode, process.args,

output=stdout, stderr=stderr)

return CompletedProcess(process.args, retcode, stdout, stderr)

def list2cmdline(seq):

"""

Translate a sequence of arguments into a command line

string, using the same rules as the MS C runtime:

1) Arguments are delimited by white space, which is either a

space or a tab.

2) A string surrounded by double quotation marks is

interpreted as a single argument, regardless of white space

contained within. A quoted string can be embedded in an

argument.

3) A double quotation mark preceded by a backslash is

interpreted as a literal double quotation mark.

4) Backslashes are interpreted literally, unless they

immediately precede a double quotation mark.

5) If backslashes immediately precede a double quotation mark,

every pair of backslashes is interpreted as a literal

backslash. If the number of backslashes is odd, the last

backslash escapes the next double quotation mark as

described in rule 3.

"""

# See

# http://msdn.microsoft.com/en-us/library/17w5ykft.aspx

# or search http://msdn.microsoft.com for

# "Parsing C++ Command-Line Arguments"

result = []

needquote = False

for arg in map(os.fsdecode, seq):

bs_buf = []

# Add a space to separate this argument from the others

if result:

result.append(' ')

needquote = (" " in arg) or ("\t" in arg) or not arg

if needquote:

result.append('"')

for c in arg:

if c == '\\':

# Don't know if we need to double yet.

bs_buf.append(c)

elif c == '"':

# Double backslashes.

result.append('\\' * len(bs_buf)*2)

bs_buf = []

result.append('\\"')

else:

# Normal char

if bs_buf:

result.extend(bs_buf)

bs_buf = []

result.append(c)

# Add remaining backslashes, if any.

if bs_buf:

result.extend(bs_buf)

if needquote:

result.extend(bs_buf)

result.append('"')

return ''.join(result)

# Various tools for executing commands and looking at their output and status.

def getstatusoutput(cmd, *, encoding=None, errors=None):

"""Return (exitcode, output) of executing cmd in a shell.

Execute the string 'cmd' in a shell with 'check_output' and

return a 2-tuple (status, output). The locale encoding is used

to decode the output and process newlines.

A trailing newline is stripped from the output.

The exit status for the command can be interpreted

according to the rules for the function 'wait'. Example:

>>> import subprocess

>>> subprocess.getstatusoutput('ls /bin/ls')

(0, '/bin/ls')

>>> subprocess.getstatusoutput('cat /bin/junk')

(1, 'cat: /bin/junk: No such file or directory')

>>> subprocess.getstatusoutput('/bin/junk')

(127, 'sh: /bin/junk: not found')

>>> subprocess.getstatusoutput('/bin/kill $$')

(-15, '')

"""

try:

data = check_output(cmd, shell=True, text=True, stderr=STDOUT,

encoding=encoding, errors=errors)

exitcode = 0

except CalledProcessError as ex:

data = ex.output

exitcode = ex.returncode

if data[-1:] == '\n':

data = data[:-1]

return exitcode, data

def getoutput(cmd, *, encoding=None, errors=None):

"""Return output (stdout or stderr) of executing cmd in a shell.

Like getstatusoutput(), except the exit status is ignored and the return

value is a string containing the command's output. Example:

>>> import subprocess

>>> subprocess.getoutput('ls /bin/ls')

'/bin/ls'

"""

return getstatusoutput(cmd, encoding=encoding, errors=errors)[1]

def _use_posix_spawn():

"""Check if posix_spawn() can be used for subprocess.

subprocess requires a posix_spawn() implementation that properly reports

errors to the parent process, & sets errno on the following failures:

* Process attribute actions failed.

* File actions failed.

* exec() failed.

Prefer an implementation which can use vfork() in some cases for best

performance.

"""

if _mswindows or not hasattr(os, 'posix_spawn'):

# os.posix_spawn() is not available

return False

if ((_env := os.environ.get('_PYTHON_SUBPROCESS_USE_POSIX_SPAWN')) in ('0', '1')):

return bool(int(_env))

if sys.platform in ('darwin', 'sunos5'):

# posix_spawn() is a syscall on both macOS and Solaris,

# and properly reports errors

return True

# Check libc name and runtime libc version

try:

ver = os.confstr('CS_GNU_LIBC_VERSION')

# parse 'glibc 2.28' as ('glibc', (2, 28))

parts = ver.split(maxsplit=1)

if len(parts) != 2:

# reject unknown format

raise ValueError

libc = parts[0]

version = tuple(map(int, parts[1].split('.')))

if sys.platform == 'linux' and libc == 'glibc' and version >= (2, 24):

# glibc 2.24 has a new Linux posix_spawn implementation using vfork

# which properly reports errors to the parent process.

return True

# Note: Don't use the implementation in earlier glibc because it doesn't

# use vfork (even if glibc 2.26 added a pipe to properly report errors

# to the parent process).

except (AttributeError, ValueError, OSError):

# os.confstr() or CS_GNU_LIBC_VERSION value not available

pass

# By default, assume that posix_spawn() does not properly report errors.

return False

# These are primarily fail-safe knobs for negatives. A True value does not

# guarantee the given libc/syscall API will be used.

_USE_POSIX_SPAWN = _use_posix_spawn()

_HAVE_POSIX_SPAWN_CLOSEFROM = hasattr(os, 'POSIX_SPAWN_CLOSEFROM')

class Popen:

""" Execute a child program in a new process.

For a complete description of the arguments see the Python documentation.

Arguments:

args: A string, or a sequence of program arguments.

bufsize: supplied as the buffering argument to the open() function when

creating the stdin/stdout/stderr pipe file objects

executable: A replacement program to execute.

stdin, stdout and stderr: These specify the executed programs' standard

input, standard output and standard error file handles, respectively.

preexec_fn: (POSIX only) An object to be called in the child process

just before the child is executed.

close_fds: Controls closing or inheriting of file descriptors.

shell: If true, the command will be executed through the shell.

cwd: Sets the current directory before the child is executed.

env: Defines the environment variables for the new process.

text: If true, decode stdin, stdout and stderr using the given encoding

(if set) or the system default otherwise.

universal_newlines: Alias of text, provided for backwards compatibility.

startupinfo and creationflags (Windows only)

restore_signals (POSIX only)

start_new_session (POSIX only)

process_group (POSIX only)

group (POSIX only)

extra_groups (POSIX only)

user (POSIX only)

umask (POSIX only)

pass_fds (POSIX only)

encoding and errors: Text mode encoding and error handling to use for

file objects stdin, stdout and stderr.

Attributes:

stdin, stdout, stderr, pid, returncode

"""

_child_created = False # Set here since __del__ checks it

def __init__(self, args, bufsize=-1, executable=None,

stdin=None, stdout=None, stderr=None,

preexec_fn=None, close_fds=True,

shell=False, cwd=None, env=None, universal_newlines=None,

startupinfo=None, creationflags=0,

restore_signals=True, start_new_session=False,

pass_fds=(), *, user=None, group=None, extra_groups=None,

encoding=None, errors=None, text=None, umask=-1, pipesize=-1,

process_group=None):

"""Create new Popen instance."""

if not _can_fork_exec:

raise OSError(

errno.ENOTSUP, f"{sys.platform} does not support processes."

)

_cleanup()

# Held while anything is calling waitpid before returncode has been

# updated to prevent clobbering returncode if wait() or poll() are

# called from multiple threads at once. After acquiring the lock,

# code must re-check self.returncode to see if another thread just

# finished a waitpid() call.

self._waitpid_lock = threading.Lock()

self._input = None

self._communication_started = False

if bufsize is None:

bufsize = -1 # Restore default

if not isinstance(bufsize, int):

raise TypeError("bufsize must be an integer")

if stdout is STDOUT:

raise ValueError("STDOUT can only be used for stderr")

if pipesize is None:

pipesize = -1 # Restore default

if not isinstance(pipesize, int):

raise TypeError("pipesize must be an integer")

if _mswindows:

if preexec_fn is not None:

raise ValueError("preexec_fn is not supported on Windows "

"platforms")

else:

# POSIX

if pass_fds and not close_fds:

warnings.warn("pass_fds overriding close_fds.", RuntimeWarning)

close_fds = True

if startupinfo is not None:

raise ValueError("startupinfo is only supported on Windows "

"platforms")

if creationflags != 0:

raise ValueError("creationflags is only supported on Windows "

"platforms")

self.args = args

self.stdin = None

self.stdout = None

self.stderr = None

self.pid = None

self.returncode = None

self.encoding = encoding

self.errors = errors

self.pipesize = pipesize

# Validate the combinations of text and universal_newlines

if (text is not None and universal_newlines is not None

and bool(universal_newlines) != bool(text)):

raise SubprocessError('Cannot disambiguate when both text '

'and universal_newlines are supplied but '

'different. Pass one or the other.')

self.text_mode = encoding or errors or text or universal_newlines

if self.text_mode and encoding is None:

self.encoding = encoding = _text_encoding()

# How long to resume waiting on a child after the first ^C.

# There is no right value for this. The purpose is to be polite

# yet remain good for interactive users trying to exit a tool.

self._sigint_wait_secs = 0.25 # 1/xkcd221.getRandomNumber()

self._closed_child_pipe_fds = False

if self.text_mode:

if bufsize == 1:

line_buffering = True

# Use the default buffer size for the underlying binary streams

# since they don't support line buffering.

bufsize = -1

else:

line_buffering = False

if process_group is None:

process_group = -1 # The internal APIs are int-only

gid = None

if group is not None:

if not hasattr(os, 'setregid'):

raise ValueError("The 'group' parameter is not supported on the "

"current platform")

elif isinstance(group, str):

try:

import grp

except ImportError:

raise ValueError("The group parameter cannot be a string "

"on systems without the grp module")

gid = grp.getgrnam(group).gr_gid

elif isinstance(group, int):

gid = group

else:

raise TypeError("Group must be a string or an integer, not {}"

.format(type(group)))

if gid < 0:

raise ValueError(f"Group ID cannot be negative, got {gid}")

gids = None

if extra_groups is not None:

if not hasattr(os, 'setgroups'):

raise ValueError("The 'extra_groups' parameter is not "

"supported on the current platform")

elif isinstance(extra_groups, str):

raise ValueError("Groups must be a list, not a string")

gids = []

for extra_group in extra_groups:

if isinstance(extra_group, str):

try:

import grp

except ImportError:

raise ValueError("Items in extra_groups cannot be "

"strings on systems without the "

"grp module")

gids.append(grp.getgrnam(extra_group).gr_gid)

elif isinstance(extra_group, int):

gids.append(extra_group)

else:

raise TypeError("Items in extra_groups must be a string "

"or integer, not {}"

.format(type(extra_group)))

# make sure that the gids are all positive here so we can do less

# checking in the C code

for gid_check in gids:

if gid_check < 0:

raise ValueError(f"Group ID cannot be negative, got {gid_check}")

uid = None

if user is not None:

if not hasattr(os, 'setreuid'):

raise ValueError("The 'user' parameter is not supported on "

"the current platform")

elif isinstance(user, str):

try:

import pwd

except ImportError:

raise ValueError("The user parameter cannot be a string "

"on systems without the pwd module")

uid = pwd.getpwnam(user).pw_uid

elif isinstance(user, int):

uid = user

else:

raise TypeError("User must be a string or an integer")

if uid < 0:

raise ValueError(f"User ID cannot be negative, got {uid}")

# Input and output objects. The general principle is like

# this:

# Parent Child

# ------ -----

# p2cwrite ---stdin---> p2cread

# c2pread <--stdout--- c2pwrite

# errread <--stderr--- errwrite

# On POSIX, the child objects are file descriptors. On

# Windows, these are Windows file handles. The parent objects

# are file descriptors on both platforms. The parent objects

# are -1 when not using PIPEs. The child objects are -1

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