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reSTify PEP 324 (#365)

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Huang Huang 2017-08-29 06:28:48 +08:00 committed by Brett Cannon
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@ -5,352 +5,359 @@ Last-Modified: $Date$
Author: Peter Astrand <astrand@lysator.liu.se> Author: Peter Astrand <astrand@lysator.liu.se>
Status: Final Status: Final
Type: Standards Track Type: Standards Track
Content-Type: text/plain Content-Type: text/x-rst
Created: 19-Nov-2003 Created: 19-Nov-2003
Python-Version: 2.4 Python-Version: 2.4
Post-History: Post-History:
Abstract Abstract
========
This PEP describes a new module for starting and communicating This PEP describes a new module for starting and communicating
with processes. with processes.
Motivation Motivation
==========
Starting new processes is a common task in any programming Starting new processes is a common task in any programming
language, and very common in a high-level language like Python. language, and very common in a high-level language like Python.
Good support for this task is needed, because: Good support for this task is needed, because:
- Inappropriate functions for starting processes could mean a - Inappropriate functions for starting processes could mean a
security risk: If the program is started through the shell, and security risk: If the program is started through the shell, and
the arguments contain shell meta characters, the result can be the arguments contain shell meta characters, the result can be
disastrous. [1] disastrous. [1]_
- It makes Python an even better replacement language for - It makes Python an even better replacement language for
over-complicated shell scripts. over-complicated shell scripts.
Currently, Python has a large number of different functions for Currently, Python has a large number of different functions for
process creation. This makes it hard for developers to choose. process creation. This makes it hard for developers to choose.
The subprocess module provides the following enhancements over The subprocess module provides the following enhancements over
previous functions: previous functions:
- One "unified" module provides all functionality from previous - One "unified" module provides all functionality from previous
functions. functions.
- Cross-process exceptions: Exceptions happening in the child - Cross-process exceptions: Exceptions happening in the child
before the new process has started to execute are re-raised in before the new process has started to execute are re-raised in
the parent. This means that it's easy to handle exec() the parent. This means that it's easy to handle ``exec()``
failures, for example. With popen2, for example, it's failures, for example. With popen2, for example, it's
impossible to detect if the execution failed. impossible to detect if the execution failed.
- A hook for executing custom code between fork and exec. This - A hook for executing custom code between fork and exec. This
can be used for, for example, changing uid. can be used for, for example, changing uid.
- No implicit call of /bin/sh. This means that there is no need - No implicit call of /bin/sh. This means that there is no need
for escaping dangerous shell meta characters. for escaping dangerous shell meta characters.
- All combinations of file descriptor redirection is possible. - All combinations of file descriptor redirection is possible.
For example, the "python-dialog" [2] needs to spawn a process For example, the "python-dialog" [2]_ needs to spawn a process
and redirect stderr, but not stdout. This is not possible with and redirect stderr, but not stdout. This is not possible with
current functions, without using temporary files. current functions, without using temporary files.
- With the subprocess module, it's possible to control if all open - With the subprocess module, it's possible to control if all open
file descriptors should be closed before the new program is file descriptors should be closed before the new program is
executed. executed.
- Support for connecting several subprocesses (shell "pipe"). - Support for connecting several subprocesses (shell "pipe").
- Universal newline support. - Universal newline support.
- A communicate() method, which makes it easy to send stdin data - A ``communicate()`` method, which makes it easy to send stdin data
and read stdout and stderr data, without risking deadlocks. and read stdout and stderr data, without risking deadlocks.
Most people are aware of the flow control issues involved with Most people are aware of the flow control issues involved with
child process communication, but not all have the patience or child process communication, but not all have the patience or
skills to write a fully correct and deadlock-free select loop. skills to write a fully correct and deadlock-free select loop.
This means that many Python applications contain race This means that many Python applications contain race
conditions. A communicate() method in the standard library conditions. A ``communicate()`` method in the standard library
solves this problem. solves this problem.
Rationale Rationale
=========
The following points summarizes the design: The following points summarizes the design:
- subprocess was based on popen2, which is tried-and-tested. - subprocess was based on popen2, which is tried-and-tested.
- The factory functions in popen2 have been removed, because I - The factory functions in popen2 have been removed, because I
consider the class constructor equally easy to work with. consider the class constructor equally easy to work with.
- popen2 contains several factory functions and classes for - popen2 contains several factory functions and classes for
different combinations of redirection. subprocess, however, different combinations of redirection. subprocess, however,
contains one single class. Since the subprocess module supports contains one single class. Since the subprocess module supports
12 different combinations of redirection, providing a class or 12 different combinations of redirection, providing a class or
function for each of them would be cumbersome and not very function for each of them would be cumbersome and not very
intuitive. Even with popen2, this is a readability problem. intuitive. Even with popen2, this is a readability problem.
For example, many people cannot tell the difference between For example, many people cannot tell the difference between
popen2.popen2 and popen2.popen4 without using the documentation. popen2.popen2 and popen2.popen4 without using the documentation.
- One small utility function is provided: subprocess.call(). It - One small utility function is provided: ``subprocess.call()``. It
aims to be an enhancement over os.system(), while still very aims to be an enhancement over ``os.system()``, while still very
easy to use: easy to use:
- It does not use the Standard C function system(), which has - It does not use the Standard C function system(), which has
limitations. limitations.
- It does not call the shell implicitly. - It does not call the shell implicitly.
- No need for quoting; using an argument list. - No need for quoting; using an argument list.
- The return value is easier to work with. - The return value is easier to work with.
The call() utility function accepts an 'args' argument, just The ``call()`` utility function accepts an 'args' argument, just
like the Popen class constructor. It waits for the command to like the ``Popen`` class constructor. It waits for the command to
complete, then returns the returncode attribute. The complete, then returns the ``returncode`` attribute. The
implementation is very simple: implementation is very simple::
def call(*args, **kwargs): def call(*args, **kwargs):
return Popen(*args, **kwargs).wait() return Popen(*args, **kwargs).wait()
The motivation behind the call() function is simple: Starting a The motivation behind the ``call()`` function is simple: Starting a
process and wait for it to finish is a common task. process and wait for it to finish is a common task.
While Popen supports a wide range of options, many users have While ``Popen`` supports a wide range of options, many users have
simple needs. Many people are using os.system() today, mainly simple needs. Many people are using ``os.system()`` today, mainly
because it provides a simple interface. Consider this example: because it provides a simple interface. Consider this example::
os.system("stty sane -F " + device) os.system("stty sane -F " + device)
With subprocess.call(), this would look like: With ``subprocess.call()``, this would look like::
subprocess.call(["stty", "sane", "-F", device]) subprocess.call(["stty", "sane", "-F", device])
or, if executing through the shell: or, if executing through the shell::
subprocess.call("stty sane -F " + device, shell=True) subprocess.call("stty sane -F " + device, shell=True)
- The "preexec" functionality makes it possible to run arbitrary - The "preexec" functionality makes it possible to run arbitrary
code between fork and exec. One might ask why there are special code between fork and exec. One might ask why there are special
arguments for setting the environment and current directory, but arguments for setting the environment and current directory, but
not for, for example, setting the uid. The answer is: not for, for example, setting the uid. The answer is:
- Changing environment and working directory is considered - Changing environment and working directory is considered
fairly common. fairly common.
- Old functions like spawn() has support for an - Old functions like ``spawn()`` has support for an
"env"-argument. "env"-argument.
- env and cwd are considered quite cross-platform: They make - env and cwd are considered quite cross-platform: They make
sense even on Windows. sense even on Windows.
- On POSIX platforms, no extension module is required: the module - On POSIX platforms, no extension module is required: the module
uses os.fork(), os.execvp() etc. uses ``os.fork()``, ``os.execvp()`` etc.
- On Windows platforms, the module requires either Mark Hammond's - On Windows platforms, the module requires either Mark Hammond's
Windows extensions[5], or a small extension module called Windows extensions [5]_, or a small extension module called
_subprocess. _subprocess.
Specification Specification
=============
This module defines one class called Popen: This module defines one class called Popen::
class Popen(args, bufsize=0, executable=None, class Popen(args, bufsize=0, executable=None,
stdin=None, stdout=None, stderr=None, stdin=None, stdout=None, stderr=None,
preexec_fn=None, close_fds=False, shell=False, preexec_fn=None, close_fds=False, shell=False,
cwd=None, env=None, universal_newlines=False, cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0): startupinfo=None, creationflags=0):
Arguments are: Arguments are:
- args should be a string, or a sequence of program arguments. - ``args`` should be a string, or a sequence of program arguments.
The program to execute is normally the first item in the args The program to execute is normally the first item in the args
sequence or string, but can be explicitly set by using the sequence or string, but can be explicitly set by using the
executable argument. executable argument.
On UNIX, with shell=False (default): In this case, the Popen On UNIX, with ``shell=False`` (default): In this case, the ``Popen``
class uses os.execvp() to execute the child program. args class uses ``os.execvp()`` to execute the child program. ``args``
should normally be a sequence. A string will be treated as a should normally be a sequence. A string will be treated as a
sequence with the string as the only item (the program to sequence with the string as the only item (the program to
execute). execute).
On UNIX, with shell=True: If args is a string, it specifies the On UNIX, with ``shell=True``: If ``args`` is a string, it specifies the
command string to execute through the shell. If args is a command string to execute through the shell. If ``args`` is a
sequence, the first item specifies the command string, and any sequence, the first item specifies the command string, and any
additional items will be treated as additional shell arguments. additional items will be treated as additional shell arguments.
On Windows: the Popen class uses CreateProcess() to execute the On Windows: the ``Popen`` class uses ``CreateProcess()`` to execute the
child program, which operates on strings. If args is a child program, which operates on strings. If ``args`` is a
sequence, it will be converted to a string using the sequence, it will be converted to a string using the
list2cmdline method. Please note that not all MS Windows ``list2cmdline`` method. Please note that not all MS Windows
applications interpret the command line the same way: The applications interpret the command line the same way: The
list2cmdline is designed for applications using the same rules ``list2cmdline`` is designed for applications using the same rules
as the MS C runtime. as the MS C runtime.
- bufsize, if given, has the same meaning as the corresponding - ``bufsize``, if given, has the same meaning as the corresponding
argument to the built-in open() function: 0 means unbuffered, 1 argument to the built-in ``open()`` function: 0 means unbuffered, 1
means line buffered, any other positive value means use a buffer means line buffered, any other positive value means use a buffer
of (approximately) that size. A negative bufsize means to use of (approximately) that size. A negative ``bufsize`` means to use
the system default, which usually means fully buffered. The the system default, which usually means fully buffered. The
default value for bufsize is 0 (unbuffered). default value for ``bufsize`` is 0 (unbuffered).
- stdin, stdout and stderr specify the executed programs' standard - ``stdin``, ``stdout`` and ``stderr`` specify the executed programs' standard
input, standard output and standard error file handles, input, standard output and standard error file handles,
respectively. Valid values are PIPE, an existing file respectively. Valid values are ``PIPE``, an existing file
descriptor (a positive integer), an existing file object, and descriptor (a positive integer), an existing file object, and
None. PIPE indicates that a new pipe to the child should be ``None``. ``PIPE`` indicates that a new pipe to the child should be
created. With None, no redirection will occur; the child's file created. With ``None``, no redirection will occur; the child's file
handles will be inherited from the parent. Additionally, stderr handles will be inherited from the parent. Additionally, ``stderr``
can be STDOUT, which indicates that the stderr data from the can be STDOUT, which indicates that the stderr data from the
applications should be captured into the same file handle as for applications should be captured into the same file handle as for
stdout. stdout.
- If preexec_fn is set to a callable object, this object will be - If ``preexec_fn`` is set to a callable object, this object will be
called in the child process just before the child is executed. called in the child process just before the child is executed.
- If close_fds is true, all file descriptors except 0, 1 and 2 - If ``close_fds`` is true, all file descriptors except 0, 1 and 2
will be closed before the child process is executed. will be closed before the child process is executed.
- If shell is true, the specified command will be executed through - If ``shell`` is true, the specified command will be executed through
the shell. the shell.
- If cwd is not None, the current directory will be changed to cwd - If ``cwd`` is not ``None``, the current directory will be changed to cwd
before the child is executed. before the child is executed.
- If env is not None, it defines the environment variables for the - If ``env`` is not ``None``, it defines the environment variables for the
new process. new process.
- If universal_newlines is true, the file objects stdout and - If ``universal_newlines`` is true, the file objects stdout and
stderr are opened as a text file, but lines may be terminated stderr are opened as a text file, but lines may be terminated
by any of '\n', the Unix end-of-line convention, '\r', the by any of ``\n``, the Unix end-of-line convention, ``\r``, the
Macintosh convention or '\r\n', the Windows convention. All of Macintosh convention or ``\r\n``, the Windows convention. All of
these external representations are seen as '\n' by the Python these external representations are seen as ``\n`` by the Python
program. Note: This feature is only available if Python is program. Note: This feature is only available if Python is
built with universal newline support (the default). Also, the built with universal newline support (the default). Also, the
newlines attribute of the file objects stdout, stdin and stderr newlines attribute of the file objects stdout, stdin and stderr
are not updated by the communicate() method. are not updated by the ``communicate()`` method.
- The startupinfo and creationflags, if given, will be passed to - The ``startupinfo`` and ``creationflags``, if given, will be passed to
the underlying CreateProcess() function. They can specify the underlying ``CreateProcess()`` function. They can specify
things such as appearance of the main window and priority for things such as appearance of the main window and priority for
the new process. (Windows only) the new process. (Windows only)
This module also defines two shortcut functions: This module also defines two shortcut functions:
- call(*args, **kwargs): - ``call(*args, **kwargs)``:
Run command with arguments. Wait for command to complete, Run command with arguments. Wait for command to complete,
then return the returncode attribute. then return the ``returncode`` attribute.
The arguments are the same as for the Popen constructor. The arguments are the same as for the Popen constructor.
Example: Example::
retcode = call(["ls", "-l"]) retcode = call(["ls", "-l"])
Exceptions Exceptions
---------- ----------
Exceptions raised in the child process, before the new program has Exceptions raised in the child process, before the new program has
started to execute, will be re-raised in the parent. started to execute, will be re-raised in the parent.
Additionally, the exception object will have one extra attribute Additionally, the exception object will have one extra attribute
called 'child_traceback', which is a string containing traceback called 'child_traceback', which is a string containing traceback
information from the child's point of view. information from the child's point of view.
The most common exception raised is OSError. This occurs, for The most common exception raised is ``OSError``. This occurs, for
example, when trying to execute a non-existent file. Applications example, when trying to execute a non-existent file. Applications
should prepare for OSErrors. should prepare for ``OSErrors``.
A ValueError will be raised if Popen is called with invalid A ``ValueError`` will be raised if Popen is called with invalid
arguments. arguments.
Security Security
-------- --------
Unlike some other popen functions, this implementation will never Unlike some other popen functions, this implementation will never
call /bin/sh implicitly. This means that all characters, call /bin/sh implicitly. This means that all characters,
including shell meta-characters, can safely be passed to child including shell meta-characters, can safely be passed to child
processes. processes.
Popen objects Popen objects
------------- -------------
Instances of the Popen class have the following methods: Instances of the Popen class have the following methods:
poll() ``poll()``
Check if child process has terminated. Returns returncode Check if child process has terminated. Returns ``returncode``
attribute. attribute.
wait() ``wait()``
Wait for child process to terminate. Returns returncode Wait for child process to terminate. Returns ``returncode``
attribute. attribute.
communicate(input=None) ``communicate(input=None)``
Interact with process: Send data to stdin. Read data from Interact with process: Send data to stdin. Read data from
stdout and stderr, until end-of-file is reached. Wait for stdout and stderr, until end-of-file is reached. Wait for
process to terminate. The optional stdin argument should be a process to terminate. The optional stdin argument should be a
string to be sent to the child process, or None, if no data string to be sent to the child process, or ``None``, if no data
should be sent to the child. should be sent to the child.
communicate() returns a tuple (stdout, stderr). ``communicate()`` returns a tuple ``(stdout, stderr)``.
Note: The data read is buffered in memory, so do not use this Note: The data read is buffered in memory, so do not use this
method if the data size is large or unlimited. method if the data size is large or unlimited.
The following attributes are also available: The following attributes are also available:
stdin ``stdin``
If the stdin argument is PIPE, this attribute is a file object If the ``stdin`` argument is ``PIPE``, this attribute is a file object
that provides input to the child process. Otherwise, it is that provides input to the child process. Otherwise, it is
None. ``None``.
stdout ``stdout``
If the stdout argument is PIPE, this attribute is a file If the ``stdout`` argument is ``PIPE``, this attribute is a file
object that provides output from the child process. object that provides output from the child process.
Otherwise, it is None. Otherwise, it is ``None``.
stderr ``stderr``
If the stderr argument is PIPE, this attribute is file object If the ``stderr`` argument is ``PIPE``, this attribute is file object
that provides error output from the child process. Otherwise, that provides error output from the child process. Otherwise,
it is None. it is ``None``.
pid ``pid``
The process ID of the child process. The process ID of the child process.
returncode ``returncode``
The child return code. A None value indicates that the The child return code. A ``None`` value indicates that the
process hasn't terminated yet. A negative value -N indicates process hasn't terminated yet. A negative value -N indicates
that the child was terminated by signal N (UNIX only). that the child was terminated by signal N (UNIX only).
Replacing older functions with the subprocess module Replacing older functions with the subprocess module
====================================================
In this section, "a ==> b" means that b can be used as a In this section, "a ==> b" means that b can be used as a
replacement for a. replacement for a.
Note: All functions in this section fail (more or less) silently Note: All functions in this section fail (more or less) silently
if the executed program cannot be found; this module raises an if the executed program cannot be found; this module raises an
OSError exception. OSError exception.
In the following examples, we assume that the subprocess module is In the following examples, we assume that the subprocess module is
imported with "from subprocess import *". imported with ``from subprocess import *``.
Replacing /bin/sh shell backquote Replacing /bin/sh shell backquote
--------------------------------- ---------------------------------
::
output=`mycmd myarg` output=`mycmd myarg`
==> ==>
output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0] output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
Replacing shell pipe line Replacing shell pipe line
------------------------- -------------------------
::
output=`dmesg | grep hda` output=`dmesg | grep hda`
==> ==>
@ -359,22 +366,23 @@ Replacing older functions with the subprocess module
output = p2.communicate()[0] output = p2.communicate()[0]
Replacing os.system() Replacing ``os.system()``
--------------------- -------------------------
::
sts = os.system("mycmd" + " myarg") sts = os.system("mycmd" + " myarg")
==> ==>
p = Popen("mycmd" + " myarg", shell=True) p = Popen("mycmd" + " myarg", shell=True)
sts = os.waitpid(p.pid, 0) sts = os.waitpid(p.pid, 0)
Note: Note:
* Calling the program through the shell is usually not required. * Calling the program through the shell is usually not required.
* It's easier to look at the returncode attribute than the * It's easier to look at the returncode attribute than the
exit status. exit status.
A more real-world example would look like this: A more real-world example would look like this::
try: try:
retcode = call("mycmd" + " myarg", shell=True) retcode = call("mycmd" + " myarg", shell=True)
@ -386,39 +394,40 @@ Replacing older functions with the subprocess module
print >>sys.stderr, "Execution failed:", e print >>sys.stderr, "Execution failed:", e
Replacing os.spawn* Replacing ``os.spawn*``
------------------- -----------------------
P_NOWAIT example: P_NOWAIT example::
pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg") pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
==> ==>
pid = Popen(["/bin/mycmd", "myarg"]).pid pid = Popen(["/bin/mycmd", "myarg"]).pid
P_WAIT example: P_WAIT example::
retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg") retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
==> ==>
retcode = call(["/bin/mycmd", "myarg"]) retcode = call(["/bin/mycmd", "myarg"])
Vector example: Vector example::
os.spawnvp(os.P_NOWAIT, path, args) os.spawnvp(os.P_NOWAIT, path, args)
==> ==>
Popen([path] + args[1:]) Popen([path] + args[1:])
Environment example: Environment example::
os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env) os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
==> ==>
Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"}) Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
Replacing os.popen* Replacing ``os.popen*``
------------------- -----------------------
::
pipe = os.popen(cmd, mode='r', bufsize) pipe = os.popen(cmd, mode='r', bufsize)
==> ==>
@ -454,12 +463,14 @@ Replacing older functions with the subprocess module
(child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout) (child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
Replacing popen2.* Replacing ``popen2.*``
------------------ ----------------------
Note: If the cmd argument to popen2 functions is a string, the Note: If the cmd argument to ``popen2`` functions is a string, the
command is executed through /bin/sh. If it is a list, the command command is executed through /bin/sh. If it is a list, the command
is directly executed. is directly executed.
::
(child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode) (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
==> ==>
@ -474,85 +485,90 @@ Replacing older functions with the subprocess module
stdin=PIPE, stdout=PIPE, close_fds=True) stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin) (child_stdout, child_stdin) = (p.stdout, p.stdin)
The popen2.Popen3 and popen3.Popen4 basically works as The ``popen2.Popen3`` and ``popen3.Popen4`` basically works as
subprocess.Popen, except that: ``subprocess.Popen``, except that:
* subprocess.Popen raises an exception if the execution fails * ``subprocess.Popen`` raises an exception if the execution fails
* the capturestderr argument is replaced with the stderr argument. * the ``capturestderr`` argument is replaced with the stderr argument.
* stdin=PIPE and stdout=PIPE must be specified. * ``stdin=PIPE`` and ``stdout=PIPE`` must be specified.
* popen2 closes all file descriptors by default, but you have to * ``popen2`` closes all file descriptors by default, but you have to
specify close_fds=True with subprocess.Popen. specify ``close_fds=True`` with ``subprocess.Popen``.
Open Issues Open Issues
===========
Some features have been requested but is not yet implemented. Some features have been requested but is not yet implemented.
This includes: This includes:
* Support for managing a whole flock of subprocesses * Support for managing a whole flock of subprocesses
* Support for managing "daemon" processes * Support for managing "daemon" processes
* Built-in method for killing subprocesses * Built-in method for killing subprocesses
While these are useful features, it's expected that these can be While these are useful features, it's expected that these can be
added later without problems. added later without problems.
* expect-like functionality, including pty support. * expect-like functionality, including pty support.
pty support is highly platform-dependent, which is a pty support is highly platform-dependent, which is a
problem. Also, there are already other modules that provide this problem. Also, there are already other modules that provide this
kind of functionality[6]. kind of functionality [6]_.
Backwards Compatibility Backwards Compatibility
=======================
Since this is a new module, no major backward compatible issues Since this is a new module, no major backward compatible issues
are expected. The module name "subprocess" might collide with are expected. The module name "subprocess" might collide with
other, previous modules[3] with the same name, but the name other, previous modules [3]_ with the same name, but the name
"subprocess" seems to be the best suggested name so far. The "subprocess" seems to be the best suggested name so far. The
first name of this module was "popen5", but this name was first name of this module was "popen5", but this name was
considered too unintuitive. For a while, the module was called considered too unintuitive. For a while, the module was called
"process", but this name is already used by Trent Mick's "process", but this name is already used by Trent Mick's
module[4]. module [4]_.
The functions and modules that this new module is trying to The functions and modules that this new module is trying to
replace (os.system, os.spawn*, os.popen*, popen2.*, commands.*) replace (``os.system``, ``os.spawn*``, ``os.popen*``, ``popen2.*``,
are expected to be available in future Python versions for a long ``commands.*``) are expected to be available in future Python versions
time, to preserve backwards compatibility. for a long time, to preserve backwards compatibility.
Reference Implementation Reference Implementation
========================
A reference implementation is available from A reference implementation is available from
http://www.lysator.liu.se/~astrand/popen5/. http://www.lysator.liu.se/~astrand/popen5/.
References References
==========
[1] Secure Programming for Linux and Unix HOWTO, section 8.3. .. [1] Secure Programming for Linux and Unix HOWTO, section 8.3.
http://www.dwheeler.com/secure-programs/ http://www.dwheeler.com/secure-programs/
[2] Python Dialog .. [2] Python Dialog
http://pythondialog.sourceforge.net/ http://pythondialog.sourceforge.net/
[3] http://www.iol.ie/~padraiga/libs/subProcess.py .. [3] http://www.iol.ie/~padraiga/libs/subProcess.py
[4] http://starship.python.net/crew/tmick/ .. [4] http://starship.python.net/crew/tmick/
[5] http://starship.python.net/crew/mhammond/win32/ .. [5] http://starship.python.net/crew/mhammond/win32/
[6] http://www.lysator.liu.se/~ceder/pcl-expect/ .. [6] http://www.lysator.liu.se/~ceder/pcl-expect/
Copyright Copyright
=========
This document has been placed in the public domain. This document has been placed in the public domain.
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