Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | :mod:`subprocess` --- Subprocess management |
| 2 | =========================================== |
| 3 | |
| 4 | .. module:: subprocess |
| 5 | :synopsis: Subprocess management. |
| 6 | .. moduleauthor:: Peter Åstrand <astrand@lysator.liu.se> |
| 7 | .. sectionauthor:: Peter Åstrand <astrand@lysator.liu.se> |
| 8 | |
| 9 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 10 | The :mod:`subprocess` module allows you to spawn new processes, connect to their |
| 11 | input/output/error pipes, and obtain their return codes. This module intends to |
Benjamin Peterson | 5eea8a7 | 2014-03-12 21:41:35 -0500 | [diff] [blame] | 12 | replace several older modules and functions:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 13 | |
| 14 | os.system |
| 15 | os.spawn* |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 16 | |
| 17 | Information about how the :mod:`subprocess` module can be used to replace these |
| 18 | modules and functions can be found in the following sections. |
| 19 | |
Benjamin Peterson | 4118174 | 2008-07-02 20:22:54 +0000 | [diff] [blame] | 20 | .. seealso:: |
| 21 | |
| 22 | :pep:`324` -- PEP proposing the subprocess module |
| 23 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 24 | |
Ezio Melotti | 402f75d | 2012-11-08 10:07:10 +0200 | [diff] [blame] | 25 | Using the :mod:`subprocess` Module |
| 26 | ---------------------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 27 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 28 | The recommended approach to invoking subprocesses is to use the :func:`run` |
Benjamin Peterson | ef9ffcb | 2015-04-14 22:12:14 -0400 | [diff] [blame] | 29 | function for all use cases it can handle. For more advanced use cases, the |
| 30 | underlying :class:`Popen` interface can be used directly. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 31 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 32 | The :func:`run` function was added in Python 3.5; if you need to retain |
| 33 | compatibility with older versions, see the :ref:`call-function-trio` section. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 34 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 35 | |
| 36 | .. function:: run(args, *, stdin=None, input=None, stdout=None, stderr=None,\ |
| 37 | shell=False, timeout=None, check=False) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 38 | |
| 39 | Run the command described by *args*. Wait for command to complete, then |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 40 | return a :class:`CompletedProcess` instance. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 41 | |
| 42 | The arguments shown above are merely the most common ones, described below |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 43 | in :ref:`frequently-used-arguments` (hence the use of keyword-only notation |
| 44 | in the abbreviated signature). The full function signature is largely the |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 45 | same as that of the :class:`Popen` constructor - apart from *timeout*, |
| 46 | *input* and *check*, all the arguments to this function are passed through to |
| 47 | that interface. |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 48 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 49 | This does not capture stdout or stderr by default. To do so, pass |
| 50 | :data:`PIPE` for the *stdout* and/or *stderr* arguments. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 51 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 52 | The *timeout* argument is passed to :meth:`Popen.communicate`. If the timeout |
| 53 | expires, the child process will be killed and waited for. The |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 54 | :exc:`TimeoutExpired` exception will be re-raised after the child process |
| 55 | has terminated. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 56 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 57 | The *input* argument is passed to :meth:`Popen.communicate` and thus to the |
| 58 | subprocess's stdin. If used it must be a byte sequence, or a string if |
| 59 | ``universal_newlines=True``. When used, the internal :class:`Popen` object |
| 60 | is automatically created with ``stdin=PIPE``, and the *stdin* argument may |
| 61 | not be used as well. |
| 62 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 63 | If *check* is True, and the process exits with a non-zero exit code, a |
| 64 | :exc:`CalledProcessError` exception will be raised. Attributes of that |
| 65 | exception hold the arguments, the exit code, and stdout and stderr if they |
| 66 | were captured. |
| 67 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 68 | Examples:: |
| 69 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 70 | >>> subprocess.run(["ls", "-l"]) # doesn't capture output |
| 71 | CompletedProcess(args=['ls', '-l'], returncode=0) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 72 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 73 | >>> subprocess.run("exit 1", shell=True, check=True) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 74 | Traceback (most recent call last): |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 75 | ... |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 76 | subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 |
| 77 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 78 | >>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE) |
| 79 | CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0, |
| 80 | stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n') |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 81 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 82 | .. versionadded:: 3.5 |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 83 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 84 | .. class:: CompletedProcess |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 85 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 86 | The return value from :func:`run`, representing a process that has finished. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 87 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 88 | .. attribute:: args |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 89 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 90 | The arguments used to launch the process. This may be a list or a string. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 91 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 92 | .. attribute:: returncode |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 93 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 94 | Exit status of the child process. Typically, an exit status of 0 indicates |
| 95 | that it ran successfully. |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 96 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 97 | A negative value ``-N`` indicates that the child was terminated by signal |
| 98 | ``N`` (POSIX only). |
| 99 | |
| 100 | .. attribute:: stdout |
| 101 | |
| 102 | Captured stdout from the child process. A bytes sequence, or a string if |
| 103 | :func:`run` was called with ``universal_newlines=True``. None if stdout |
| 104 | was not captured. |
| 105 | |
| 106 | If you ran the process with ``stderr=subprocess.STDOUT``, stdout and |
| 107 | stderr will be combined in this attribute, and :attr:`stderr` will be |
| 108 | None. |
| 109 | |
| 110 | .. attribute:: stderr |
| 111 | |
| 112 | Captured stderr from the child process. A bytes sequence, or a string if |
| 113 | :func:`run` was called with ``universal_newlines=True``. None if stderr |
| 114 | was not captured. |
| 115 | |
| 116 | .. method:: check_returncode() |
| 117 | |
| 118 | If :attr:`returncode` is non-zero, raise a :exc:`CalledProcessError`. |
| 119 | |
| 120 | .. versionadded:: 3.5 |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 121 | |
| 122 | .. data:: DEVNULL |
| 123 | |
| 124 | Special value that can be used as the *stdin*, *stdout* or *stderr* argument |
| 125 | to :class:`Popen` and indicates that the special file :data:`os.devnull` |
| 126 | will be used. |
| 127 | |
| 128 | .. versionadded:: 3.3 |
| 129 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 130 | |
| 131 | .. data:: PIPE |
| 132 | |
| 133 | Special value that can be used as the *stdin*, *stdout* or *stderr* argument |
| 134 | to :class:`Popen` and indicates that a pipe to the standard stream should be |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 135 | opened. Most useful with :meth:`Popen.communicate`. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 136 | |
| 137 | |
| 138 | .. data:: STDOUT |
| 139 | |
| 140 | Special value that can be used as the *stderr* argument to :class:`Popen` and |
| 141 | indicates that standard error should go into the same handle as standard |
| 142 | output. |
| 143 | |
| 144 | |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 145 | .. exception:: SubprocessError |
| 146 | |
| 147 | Base class for all other exceptions from this module. |
| 148 | |
| 149 | .. versionadded:: 3.3 |
| 150 | |
| 151 | |
| 152 | .. exception:: TimeoutExpired |
| 153 | |
| 154 | Subclass of :exc:`SubprocessError`, raised when a timeout expires |
| 155 | while waiting for a child process. |
| 156 | |
| 157 | .. attribute:: cmd |
| 158 | |
| 159 | Command that was used to spawn the child process. |
| 160 | |
| 161 | .. attribute:: timeout |
| 162 | |
| 163 | Timeout in seconds. |
| 164 | |
| 165 | .. attribute:: output |
| 166 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 167 | Output of the child process if it was captured by :func:`run` or |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 168 | :func:`check_output`. Otherwise, ``None``. |
| 169 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 170 | .. attribute:: stdout |
| 171 | |
| 172 | Alias for output, for symmetry with :attr:`stderr`. |
| 173 | |
| 174 | .. attribute:: stderr |
| 175 | |
| 176 | Stderr output of the child process if it was captured by :func:`run`. |
| 177 | Otherwise, ``None``. |
| 178 | |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 179 | .. versionadded:: 3.3 |
| 180 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 181 | .. versionchanged:: 3.5 |
| 182 | *stdout* and *stderr* attributes added |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 183 | |
| 184 | .. exception:: CalledProcessError |
| 185 | |
| 186 | Subclass of :exc:`SubprocessError`, raised when a process run by |
| 187 | :func:`check_call` or :func:`check_output` returns a non-zero exit status. |
| 188 | |
| 189 | .. attribute:: returncode |
| 190 | |
| 191 | Exit status of the child process. |
| 192 | |
| 193 | .. attribute:: cmd |
| 194 | |
| 195 | Command that was used to spawn the child process. |
| 196 | |
| 197 | .. attribute:: output |
| 198 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 199 | Output of the child process if it was captured by :func:`run` or |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 200 | :func:`check_output`. Otherwise, ``None``. |
| 201 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 202 | .. attribute:: stdout |
| 203 | |
| 204 | Alias for output, for symmetry with :attr:`stderr`. |
| 205 | |
| 206 | .. attribute:: stderr |
| 207 | |
| 208 | Stderr output of the child process if it was captured by :func:`run`. |
| 209 | Otherwise, ``None``. |
| 210 | |
| 211 | .. versionchanged:: 3.5 |
| 212 | *stdout* and *stderr* attributes added |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 213 | |
| 214 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 215 | .. _frequently-used-arguments: |
| 216 | |
| 217 | Frequently Used Arguments |
| 218 | ^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 219 | |
| 220 | To support a wide variety of use cases, the :class:`Popen` constructor (and |
| 221 | the convenience functions) accept a large number of optional arguments. For |
| 222 | most typical use cases, many of these arguments can be safely left at their |
| 223 | default values. The arguments that are most commonly needed are: |
| 224 | |
| 225 | *args* is required for all calls and should be a string, or a sequence of |
| 226 | program arguments. Providing a sequence of arguments is generally |
| 227 | preferred, as it allows the module to take care of any required escaping |
| 228 | and quoting of arguments (e.g. to permit spaces in file names). If passing |
| 229 | a single string, either *shell* must be :const:`True` (see below) or else |
| 230 | the string must simply name the program to be executed without specifying |
| 231 | any arguments. |
| 232 | |
| 233 | *stdin*, *stdout* and *stderr* specify the executed program's standard input, |
| 234 | standard output and standard error file handles, respectively. Valid values |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 235 | are :data:`PIPE`, :data:`DEVNULL`, an existing file descriptor (a positive |
| 236 | integer), an existing file object, and ``None``. :data:`PIPE` indicates |
| 237 | that a new pipe to the child should be created. :data:`DEVNULL` indicates |
| 238 | that the special file :data:`os.devnull` will be used. With the default |
| 239 | settings of ``None``, no redirection will occur; the child's file handles |
| 240 | will be inherited from the parent. Additionally, *stderr* can be |
| 241 | :data:`STDOUT`, which indicates that the stderr data from the child |
| 242 | process should be captured into the same file handle as for *stdout*. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 243 | |
R David Murray | 1b00f25 | 2012-08-15 10:43:58 -0400 | [diff] [blame] | 244 | .. index:: |
| 245 | single: universal newlines; subprocess module |
| 246 | |
Ronald Oussoren | 385521c | 2013-07-07 09:26:45 +0200 | [diff] [blame] | 247 | If *universal_newlines* is ``False`` the file objects *stdin*, *stdout* and |
| 248 | *stderr* will be opened as binary streams, and no line ending conversion is |
| 249 | done. |
| 250 | |
| 251 | If *universal_newlines* is ``True``, these file objects |
| 252 | will be opened as text streams in :term:`universal newlines` mode |
R David Murray | 0689ce4 | 2012-08-15 11:13:31 -0400 | [diff] [blame] | 253 | using the encoding returned by :func:`locale.getpreferredencoding(False) |
Ronald Oussoren | 385521c | 2013-07-07 09:26:45 +0200 | [diff] [blame] | 254 | <locale.getpreferredencoding>`. For *stdin*, line ending characters |
R David Murray | 0689ce4 | 2012-08-15 11:13:31 -0400 | [diff] [blame] | 255 | ``'\n'`` in the input will be converted to the default line separator |
| 256 | :data:`os.linesep`. For *stdout* and *stderr*, all line endings in the |
| 257 | output will be converted to ``'\n'``. For more information see the |
| 258 | documentation of the :class:`io.TextIOWrapper` class when the *newline* |
| 259 | argument to its constructor is ``None``. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 260 | |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 261 | .. note:: |
| 262 | |
Gregory P. Smith | 1f8a40b | 2013-03-20 18:32:03 -0700 | [diff] [blame] | 263 | The newlines attribute of the file objects :attr:`Popen.stdin`, |
| 264 | :attr:`Popen.stdout` and :attr:`Popen.stderr` are not updated by |
| 265 | the :meth:`Popen.communicate` method. |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 266 | |
| 267 | If *shell* is ``True``, the specified command will be executed through |
Ezio Melotti | 186d523 | 2012-09-15 08:34:08 +0300 | [diff] [blame] | 268 | the shell. This can be useful if you are using Python primarily for the |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 269 | enhanced control flow it offers over most system shells and still want |
Ezio Melotti | 186d523 | 2012-09-15 08:34:08 +0300 | [diff] [blame] | 270 | convenient access to other shell features such as shell pipes, filename |
| 271 | wildcards, environment variable expansion, and expansion of ``~`` to a |
| 272 | user's home directory. However, note that Python itself offers |
| 273 | implementations of many shell-like features (in particular, :mod:`glob`, |
| 274 | :mod:`fnmatch`, :func:`os.walk`, :func:`os.path.expandvars`, |
| 275 | :func:`os.path.expanduser`, and :mod:`shutil`). |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 276 | |
Andrew Svetlov | 4805fa8 | 2012-08-13 22:11:14 +0300 | [diff] [blame] | 277 | .. versionchanged:: 3.3 |
| 278 | When *universal_newlines* is ``True``, the class uses the encoding |
| 279 | :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>` |
| 280 | instead of ``locale.getpreferredencoding()``. See the |
| 281 | :class:`io.TextIOWrapper` class for more information on this change. |
| 282 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 283 | .. note:: |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 284 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 285 | Read the `Security Considerations`_ section before using ``shell=True``. |
Andrew Svetlov | c2415eb | 2012-10-28 11:42:26 +0200 | [diff] [blame] | 286 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 287 | These options, along with all of the other options, are described in more |
| 288 | detail in the :class:`Popen` constructor documentation. |
| 289 | |
| 290 | |
Sandro Tosi | 1526ad1 | 2011-12-25 11:27:37 +0100 | [diff] [blame] | 291 | Popen Constructor |
Sandro Tosi | 3e6c814 | 2011-12-25 17:14:11 +0100 | [diff] [blame] | 292 | ^^^^^^^^^^^^^^^^^ |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 293 | |
| 294 | The underlying process creation and management in this module is handled by |
| 295 | the :class:`Popen` class. It offers a lot of flexibility so that developers |
| 296 | are able to handle the less common cases not covered by the convenience |
| 297 | functions. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 298 | |
| 299 | |
Gregory P. Smith | a1ed539 | 2013-03-23 11:44:25 -0700 | [diff] [blame] | 300 | .. class:: Popen(args, bufsize=-1, executable=None, stdin=None, stdout=None, \ |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 301 | stderr=None, preexec_fn=None, close_fds=True, shell=False, \ |
| 302 | cwd=None, env=None, universal_newlines=False, \ |
| 303 | startupinfo=None, creationflags=0, restore_signals=True, \ |
| 304 | start_new_session=False, pass_fds=()) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 305 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 306 | Execute a child program in a new process. On POSIX, the class uses |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 307 | :meth:`os.execvp`-like behavior to execute the child program. On Windows, |
| 308 | the class uses the Windows ``CreateProcess()`` function. The arguments to |
| 309 | :class:`Popen` are as follows. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 310 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 311 | *args* should be a sequence of program arguments or else a single string. |
| 312 | By default, the program to execute is the first item in *args* if *args* is |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 313 | a sequence. If *args* is a string, the interpretation is |
| 314 | platform-dependent and described below. See the *shell* and *executable* |
| 315 | arguments for additional differences from the default behavior. Unless |
| 316 | otherwise stated, it is recommended to pass *args* as a sequence. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 317 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 318 | On POSIX, if *args* is a string, the string is interpreted as the name or |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 319 | path of the program to execute. However, this can only be done if not |
| 320 | passing arguments to the program. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 321 | |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 322 | .. note:: |
| 323 | |
| 324 | :meth:`shlex.split` can be useful when determining the correct |
| 325 | tokenization for *args*, especially in complex cases:: |
| 326 | |
| 327 | >>> import shlex, subprocess |
R. David Murray | 73bc75b | 2010-02-05 16:25:12 +0000 | [diff] [blame] | 328 | >>> command_line = input() |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 329 | /bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'" |
| 330 | >>> args = shlex.split(command_line) |
| 331 | >>> print(args) |
| 332 | ['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"] |
| 333 | >>> p = subprocess.Popen(args) # Success! |
| 334 | |
| 335 | Note in particular that options (such as *-input*) and arguments (such |
| 336 | as *eggs.txt*) that are separated by whitespace in the shell go in separate |
| 337 | list elements, while arguments that need quoting or backslash escaping when |
| 338 | used in the shell (such as filenames containing spaces or the *echo* command |
| 339 | shown above) are single list elements. |
| 340 | |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 341 | On Windows, if *args* is a sequence, it will be converted to a string in a |
| 342 | manner described in :ref:`converting-argument-sequence`. This is because |
| 343 | the underlying ``CreateProcess()`` operates on strings. |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 344 | |
| 345 | The *shell* argument (which defaults to *False*) specifies whether to use |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 346 | the shell as the program to execute. If *shell* is *True*, it is |
| 347 | recommended to pass *args* as a string rather than as a sequence. |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 348 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 349 | On POSIX with ``shell=True``, the shell defaults to :file:`/bin/sh`. If |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 350 | *args* is a string, the string specifies the command |
| 351 | to execute through the shell. This means that the string must be |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 352 | formatted exactly as it would be when typed at the shell prompt. This |
| 353 | includes, for example, quoting or backslash escaping filenames with spaces in |
| 354 | them. If *args* is a sequence, the first item specifies the command string, and |
| 355 | any additional items will be treated as additional arguments to the shell |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 356 | itself. That is to say, :class:`Popen` does the equivalent of:: |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 357 | |
| 358 | Popen(['/bin/sh', '-c', args[0], args[1], ...]) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 359 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 360 | On Windows with ``shell=True``, the :envvar:`COMSPEC` environment variable |
| 361 | specifies the default shell. The only time you need to specify |
| 362 | ``shell=True`` on Windows is when the command you wish to execute is built |
| 363 | into the shell (e.g. :command:`dir` or :command:`copy`). You do not need |
| 364 | ``shell=True`` to run a batch file or console-based executable. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 365 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 366 | .. note:: |
Chris Jerdonek | cc32a68 | 2012-10-10 22:52:22 -0700 | [diff] [blame] | 367 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 368 | Read the `Security Considerations`_ section before using ``shell=True``. |
Chris Jerdonek | cc32a68 | 2012-10-10 22:52:22 -0700 | [diff] [blame] | 369 | |
Antoine Pitrou | afe8d06 | 2014-09-21 21:10:56 +0200 | [diff] [blame] | 370 | *bufsize* will be supplied as the corresponding argument to the |
| 371 | :func:`open` function when creating the stdin/stdout/stderr pipe |
| 372 | file objects: |
| 373 | |
| 374 | - :const:`0` means unbuffered (read and write are one |
| 375 | system call and can return short) |
| 376 | - :const:`1` means line buffered |
| 377 | (only usable if ``universal_newlines=True`` i.e., in a text mode) |
| 378 | - any other positive value means use a buffer of approximately that |
| 379 | size |
| 380 | - negative bufsize (the default) means the system default of |
| 381 | io.DEFAULT_BUFFER_SIZE will be used. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 382 | |
Georg Brandl | 37b70bb | 2013-11-25 08:48:37 +0100 | [diff] [blame] | 383 | .. versionchanged:: 3.3.1 |
Gregory P. Smith | a1ed539 | 2013-03-23 11:44:25 -0700 | [diff] [blame] | 384 | *bufsize* now defaults to -1 to enable buffering by default to match the |
Georg Brandl | 37b70bb | 2013-11-25 08:48:37 +0100 | [diff] [blame] | 385 | behavior that most code expects. In versions prior to Python 3.2.4 and |
| 386 | 3.3.1 it incorrectly defaulted to :const:`0` which was unbuffered |
| 387 | and allowed short reads. This was unintentional and did not match the |
| 388 | behavior of Python 2 as most code expected. |
Antoine Pitrou | 4b87620 | 2010-06-02 17:10:49 +0000 | [diff] [blame] | 389 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 390 | The *executable* argument specifies a replacement program to execute. It |
| 391 | is very seldom needed. When ``shell=False``, *executable* replaces the |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 392 | program to execute specified by *args*. However, the original *args* is |
| 393 | still passed to the program. Most programs treat the program specified |
| 394 | by *args* as the command name, which can then be different from the program |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 395 | actually executed. On POSIX, the *args* name |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 396 | becomes the display name for the executable in utilities such as |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 397 | :program:`ps`. If ``shell=True``, on POSIX the *executable* argument |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 398 | specifies a replacement shell for the default :file:`/bin/sh`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 399 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 400 | *stdin*, *stdout* and *stderr* specify the executed program's standard input, |
Georg Brandl | af265f4 | 2008-12-07 15:06:20 +0000 | [diff] [blame] | 401 | standard output and standard error file handles, respectively. Valid values |
Ross Lagerwall | ba102ec | 2011-03-16 18:40:25 +0200 | [diff] [blame] | 402 | are :data:`PIPE`, :data:`DEVNULL`, an existing file descriptor (a positive |
| 403 | integer), an existing :term:`file object`, and ``None``. :data:`PIPE` |
| 404 | indicates that a new pipe to the child should be created. :data:`DEVNULL` |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 405 | indicates that the special file :data:`os.devnull` will be used. With the |
| 406 | default settings of ``None``, no redirection will occur; the child's file |
| 407 | handles will be inherited from the parent. Additionally, *stderr* can be |
| 408 | :data:`STDOUT`, which indicates that the stderr data from the applications |
| 409 | should be captured into the same file handle as for stdout. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 410 | |
| 411 | If *preexec_fn* is set to a callable object, this object will be called in the |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 412 | child process just before the child is executed. |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 413 | (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 414 | |
| 415 | .. warning:: |
| 416 | |
| 417 | The *preexec_fn* parameter is not safe to use in the presence of threads |
| 418 | in your application. The child process could deadlock before exec is |
| 419 | called. |
| 420 | If you must use it, keep it trivial! Minimize the number of libraries |
| 421 | you call into. |
| 422 | |
| 423 | .. note:: |
| 424 | |
| 425 | If you need to modify the environment for the child use the *env* |
| 426 | parameter rather than doing it in a *preexec_fn*. |
| 427 | The *start_new_session* parameter can take the place of a previously |
| 428 | common use of *preexec_fn* to call os.setsid() in the child. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 429 | |
| 430 | If *close_fds* is true, all file descriptors except :const:`0`, :const:`1` and |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 431 | :const:`2` will be closed before the child process is executed. (POSIX only). |
| 432 | The default varies by platform: Always true on POSIX. On Windows it is |
Gregory P. Smith | 8edd99d | 2010-12-14 13:43:30 +0000 | [diff] [blame] | 433 | true when *stdin*/*stdout*/*stderr* are :const:`None`, false otherwise. |
Gregory P. Smith | d23047b | 2010-12-04 09:10:44 +0000 | [diff] [blame] | 434 | On Windows, if *close_fds* is true then no handles will be inherited by the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 435 | child process. Note that on Windows, you cannot set *close_fds* to true and |
| 436 | also redirect the standard handles by setting *stdin*, *stdout* or *stderr*. |
| 437 | |
Gregory P. Smith | 8edd99d | 2010-12-14 13:43:30 +0000 | [diff] [blame] | 438 | .. versionchanged:: 3.2 |
| 439 | The default for *close_fds* was changed from :const:`False` to |
| 440 | what is described above. |
| 441 | |
| 442 | *pass_fds* is an optional sequence of file descriptors to keep open |
| 443 | between the parent and child. Providing any *pass_fds* forces |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 444 | *close_fds* to be :const:`True`. (POSIX only) |
Gregory P. Smith | 8edd99d | 2010-12-14 13:43:30 +0000 | [diff] [blame] | 445 | |
| 446 | .. versionadded:: 3.2 |
| 447 | The *pass_fds* parameter was added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 448 | |
Chris Jerdonek | ec3ea94 | 2012-09-30 00:10:28 -0700 | [diff] [blame] | 449 | If *cwd* is not ``None``, the function changes the working directory to |
| 450 | *cwd* before executing the child. In particular, the function looks for |
| 451 | *executable* (or for the first item in *args*) relative to *cwd* if the |
| 452 | executable path is a relative path. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 453 | |
Serhiy Storchaka | fbc1c26 | 2013-11-29 12:17:13 +0200 | [diff] [blame] | 454 | If *restore_signals* is true (the default) all signals that Python has set to |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 455 | SIG_IGN are restored to SIG_DFL in the child process before the exec. |
| 456 | Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 457 | (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 458 | |
| 459 | .. versionchanged:: 3.2 |
| 460 | *restore_signals* was added. |
| 461 | |
Serhiy Storchaka | fbc1c26 | 2013-11-29 12:17:13 +0200 | [diff] [blame] | 462 | If *start_new_session* is true the setsid() system call will be made in the |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 463 | child process prior to the execution of the subprocess. (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 464 | |
| 465 | .. versionchanged:: 3.2 |
| 466 | *start_new_session* was added. |
| 467 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 468 | If *env* is not ``None``, it must be a mapping that defines the environment |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 469 | variables for the new process; these are used instead of the default |
| 470 | behavior of inheriting the current process' environment. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 471 | |
R. David Murray | 1055e89 | 2009-04-16 18:15:32 +0000 | [diff] [blame] | 472 | .. note:: |
R. David Murray | f4ac149 | 2009-04-15 22:35:15 +0000 | [diff] [blame] | 473 | |
Georg Brandl | 2708f3a | 2009-12-20 14:38:23 +0000 | [diff] [blame] | 474 | If specified, *env* must provide any variables required for the program to |
| 475 | execute. On Windows, in order to run a `side-by-side assembly`_ the |
| 476 | specified *env* **must** include a valid :envvar:`SystemRoot`. |
R. David Murray | f4ac149 | 2009-04-15 22:35:15 +0000 | [diff] [blame] | 477 | |
R. David Murray | 1055e89 | 2009-04-16 18:15:32 +0000 | [diff] [blame] | 478 | .. _side-by-side assembly: http://en.wikipedia.org/wiki/Side-by-Side_Assembly |
| 479 | |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 480 | If *universal_newlines* is ``True``, the file objects *stdin*, *stdout* |
R David Murray | 1b00f25 | 2012-08-15 10:43:58 -0400 | [diff] [blame] | 481 | and *stderr* are opened as text streams in universal newlines mode, as |
Ronald Oussoren | a686505 | 2013-07-06 10:23:59 +0200 | [diff] [blame] | 482 | described above in :ref:`frequently-used-arguments`, otherwise they are |
| 483 | opened as binary streams. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 484 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 485 | If given, *startupinfo* will be a :class:`STARTUPINFO` object, which is |
| 486 | passed to the underlying ``CreateProcess`` function. |
Brian Curtin | 3040193 | 2011-04-29 22:20:57 -0500 | [diff] [blame] | 487 | *creationflags*, if given, can be :data:`CREATE_NEW_CONSOLE` or |
| 488 | :data:`CREATE_NEW_PROCESS_GROUP`. (Windows only) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 489 | |
Gregory P. Smith | 6b65745 | 2011-05-11 21:42:08 -0700 | [diff] [blame] | 490 | Popen objects are supported as context managers via the :keyword:`with` statement: |
| 491 | on exit, standard file descriptors are closed, and the process is waited for. |
Brian Curtin | 79cdb66 | 2010-12-03 02:46:02 +0000 | [diff] [blame] | 492 | :: |
| 493 | |
| 494 | with Popen(["ifconfig"], stdout=PIPE) as proc: |
| 495 | log.write(proc.stdout.read()) |
| 496 | |
| 497 | .. versionchanged:: 3.2 |
| 498 | Added context manager support. |
| 499 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 500 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 501 | Exceptions |
| 502 | ^^^^^^^^^^ |
| 503 | |
| 504 | Exceptions raised in the child process, before the new program has started to |
| 505 | execute, will be re-raised in the parent. Additionally, the exception object |
| 506 | will have one extra attribute called :attr:`child_traceback`, which is a string |
Georg Brandl | 8167561 | 2010-08-26 14:30:56 +0000 | [diff] [blame] | 507 | containing traceback information from the child's point of view. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 508 | |
| 509 | The most common exception raised is :exc:`OSError`. This occurs, for example, |
| 510 | when trying to execute a non-existent file. Applications should prepare for |
| 511 | :exc:`OSError` exceptions. |
| 512 | |
| 513 | A :exc:`ValueError` will be raised if :class:`Popen` is called with invalid |
| 514 | arguments. |
| 515 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 516 | :func:`check_call` and :func:`check_output` will raise |
| 517 | :exc:`CalledProcessError` if the called process returns a non-zero return |
| 518 | code. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 519 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 520 | All of the functions and methods that accept a *timeout* parameter, such as |
| 521 | :func:`call` and :meth:`Popen.communicate` will raise :exc:`TimeoutExpired` if |
| 522 | the timeout expires before the process exits. |
| 523 | |
Ronald Oussoren | c157790 | 2011-03-16 10:03:10 -0400 | [diff] [blame] | 524 | Exceptions defined in this module all inherit from :exc:`SubprocessError`. |
Gregory P. Smith | 54d412e | 2011-03-14 14:08:43 -0400 | [diff] [blame] | 525 | |
| 526 | .. versionadded:: 3.3 |
| 527 | The :exc:`SubprocessError` base class was added. |
| 528 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 529 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 530 | Security Considerations |
| 531 | ----------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 532 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 533 | Unlike some other popen functions, this implementation will never |
| 534 | implicitly call a system shell. This means that all characters, |
| 535 | including shell metacharacters, can safely be passed to child processes. |
| 536 | If the shell is invoked explicitly, via ``shell=True``, it is the application's |
| 537 | responsibility to ensure that all whitespace and metacharacters are |
| 538 | quoted appropriately to avoid |
| 539 | `shell injection <http://en.wikipedia.org/wiki/Shell_injection#Shell_injection>`_ |
| 540 | vulnerabilities. |
| 541 | |
| 542 | When using ``shell=True``, the :func:`shlex.quote` function can be |
| 543 | used to properly escape whitespace and shell metacharacters in strings |
| 544 | that are going to be used to construct shell commands. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 545 | |
| 546 | |
| 547 | Popen Objects |
| 548 | ------------- |
| 549 | |
| 550 | Instances of the :class:`Popen` class have the following methods: |
| 551 | |
| 552 | |
| 553 | .. method:: Popen.poll() |
| 554 | |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 555 | Check if child process has terminated. Set and return |
| 556 | :attr:`~Popen.returncode` attribute. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 557 | |
| 558 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 559 | .. method:: Popen.wait(timeout=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 560 | |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 561 | Wait for child process to terminate. Set and return |
| 562 | :attr:`~Popen.returncode` attribute. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 563 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 564 | If the process does not terminate after *timeout* seconds, raise a |
| 565 | :exc:`TimeoutExpired` exception. It is safe to catch this exception and |
| 566 | retry the wait. |
| 567 | |
Victor Stinner | 0717124 | 2014-02-24 13:18:47 +0100 | [diff] [blame] | 568 | .. note:: |
| 569 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 570 | This will deadlock when using ``stdout=PIPE`` or ``stderr=PIPE`` |
| 571 | and the child process generates enough output to a pipe such that |
| 572 | it blocks waiting for the OS pipe buffer to accept more data. |
| 573 | Use :meth:`Popen.communicate` when using pipes to avoid that. |
| 574 | |
| 575 | .. note:: |
| 576 | |
Victor Stinner | 0717124 | 2014-02-24 13:18:47 +0100 | [diff] [blame] | 577 | The function is implemented using a busy loop (non-blocking call and |
| 578 | short sleeps). Use the :mod:`asyncio` module for an asynchronous wait: |
| 579 | see :class:`asyncio.create_subprocess_exec`. |
| 580 | |
Reid Kleckner | 28f1303 | 2011-03-14 12:36:53 -0400 | [diff] [blame] | 581 | .. versionchanged:: 3.3 |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 582 | *timeout* was added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 583 | |
Gregory P. Smith | bbe3335 | 2014-02-11 09:21:03 -0800 | [diff] [blame] | 584 | .. deprecated:: 3.4 |
| 585 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 586 | Do not use the *endtime* parameter. It is was unintentionally |
| 587 | exposed in 3.3 but was left undocumented as it was intended to be |
| 588 | private for internal use. Use *timeout* instead. |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 589 | |
| 590 | .. method:: Popen.communicate(input=None, timeout=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 591 | |
| 592 | Interact with process: Send data to stdin. Read data from stdout and stderr, |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 593 | until end-of-file is reached. Wait for process to terminate. The optional |
Gregory P. Smith | a454ef6 | 2011-05-22 22:29:49 -0700 | [diff] [blame] | 594 | *input* argument should be data to be sent to the child process, or |
| 595 | ``None``, if no data should be sent to the child. The type of *input* |
| 596 | must be bytes or, if *universal_newlines* was ``True``, a string. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 597 | |
Victor Stinner | 3989205 | 2014-10-14 00:52:07 +0200 | [diff] [blame] | 598 | :meth:`communicate` returns a tuple ``(stdout_data, stderr_data)``. |
Andrew Kuchling | 4f7b0c3 | 2014-04-14 15:08:18 -0400 | [diff] [blame] | 599 | The data will be bytes or, if *universal_newlines* was ``True``, strings. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 600 | |
Guido van Rossum | 0d3fb8a | 2007-11-26 23:23:18 +0000 | [diff] [blame] | 601 | Note that if you want to send data to the process's stdin, you need to create |
| 602 | the Popen object with ``stdin=PIPE``. Similarly, to get anything other than |
| 603 | ``None`` in the result tuple, you need to give ``stdout=PIPE`` and/or |
| 604 | ``stderr=PIPE`` too. |
| 605 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 606 | If the process does not terminate after *timeout* seconds, a |
| 607 | :exc:`TimeoutExpired` exception will be raised. Catching this exception and |
| 608 | retrying communication will not lose any output. |
| 609 | |
| 610 | The child process is not killed if the timeout expires, so in order to |
| 611 | cleanup properly a well-behaved application should kill the child process and |
| 612 | finish communication:: |
| 613 | |
| 614 | proc = subprocess.Popen(...) |
| 615 | try: |
| 616 | outs, errs = proc.communicate(timeout=15) |
| 617 | except TimeoutExpired: |
| 618 | proc.kill() |
| 619 | outs, errs = proc.communicate() |
| 620 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 621 | .. note:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 622 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 623 | The data read is buffered in memory, so do not use this method if the data |
| 624 | size is large or unlimited. |
| 625 | |
Reid Kleckner | 28f1303 | 2011-03-14 12:36:53 -0400 | [diff] [blame] | 626 | .. versionchanged:: 3.3 |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 627 | *timeout* was added. |
| 628 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 629 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 630 | .. method:: Popen.send_signal(signal) |
| 631 | |
| 632 | Sends the signal *signal* to the child. |
| 633 | |
| 634 | .. note:: |
| 635 | |
Brian Curtin | eb24d74 | 2010-04-12 17:16:38 +0000 | [diff] [blame] | 636 | On Windows, SIGTERM is an alias for :meth:`terminate`. CTRL_C_EVENT and |
Senthil Kumaran | 916bd38 | 2010-10-15 12:55:19 +0000 | [diff] [blame] | 637 | CTRL_BREAK_EVENT can be sent to processes started with a *creationflags* |
Brian Curtin | eb24d74 | 2010-04-12 17:16:38 +0000 | [diff] [blame] | 638 | parameter which includes `CREATE_NEW_PROCESS_GROUP`. |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 639 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 640 | |
| 641 | .. method:: Popen.terminate() |
| 642 | |
| 643 | Stop the child. On Posix OSs the method sends SIGTERM to the |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 644 | child. On Windows the Win32 API function :c:func:`TerminateProcess` is called |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 645 | to stop the child. |
| 646 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 647 | |
| 648 | .. method:: Popen.kill() |
| 649 | |
| 650 | Kills the child. On Posix OSs the function sends SIGKILL to the child. |
| 651 | On Windows :meth:`kill` is an alias for :meth:`terminate`. |
| 652 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 653 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 654 | The following attributes are also available: |
| 655 | |
Gregory P. Smith | 024c5ee | 2014-04-29 11:33:23 -0700 | [diff] [blame] | 656 | .. attribute:: Popen.args |
| 657 | |
| 658 | The *args* argument as it was passed to :class:`Popen` -- a |
| 659 | sequence of program arguments or else a single string. |
| 660 | |
| 661 | .. versionadded:: 3.3 |
Georg Brandl | 734e268 | 2008-08-12 08:18:18 +0000 | [diff] [blame] | 662 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 663 | .. attribute:: Popen.stdin |
| 664 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 665 | If the *stdin* argument was :data:`PIPE`, this attribute is a writeable |
| 666 | stream object as returned by :func:`open`. If the *universal_newlines* |
| 667 | argument was ``True``, the stream is a text stream, otherwise it is a byte |
| 668 | stream. If the *stdin* argument was not :data:`PIPE`, this attribute is |
| 669 | ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 670 | |
| 671 | |
| 672 | .. attribute:: Popen.stdout |
| 673 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 674 | If the *stdout* argument was :data:`PIPE`, this attribute is a readable |
| 675 | stream object as returned by :func:`open`. Reading from the stream provides |
| 676 | output from the child process. If the *universal_newlines* argument was |
| 677 | ``True``, the stream is a text stream, otherwise it is a byte stream. If the |
| 678 | *stdout* argument was not :data:`PIPE`, this attribute is ``None``. |
Benjamin Peterson | af69fe2 | 2014-01-18 00:49:04 -0500 | [diff] [blame] | 679 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 680 | |
| 681 | .. attribute:: Popen.stderr |
| 682 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 683 | If the *stderr* argument was :data:`PIPE`, this attribute is a readable |
| 684 | stream object as returned by :func:`open`. Reading from the stream provides |
| 685 | error output from the child process. If the *universal_newlines* argument was |
| 686 | ``True``, the stream is a text stream, otherwise it is a byte stream. If the |
| 687 | *stderr* argument was not :data:`PIPE`, this attribute is ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 688 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 689 | .. warning:: |
| 690 | |
| 691 | Use :meth:`~Popen.communicate` rather than :attr:`.stdin.write <Popen.stdin>`, |
| 692 | :attr:`.stdout.read <Popen.stdout>` or :attr:`.stderr.read <Popen.stderr>` to avoid |
| 693 | deadlocks due to any of the other OS pipe buffers filling up and blocking the |
| 694 | child process. |
| 695 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 696 | |
| 697 | .. attribute:: Popen.pid |
| 698 | |
| 699 | The process ID of the child process. |
| 700 | |
Georg Brandl | 58bfdca | 2010-03-21 09:50:49 +0000 | [diff] [blame] | 701 | Note that if you set the *shell* argument to ``True``, this is the process ID |
| 702 | of the spawned shell. |
| 703 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 704 | |
| 705 | .. attribute:: Popen.returncode |
| 706 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 707 | The child return code, set by :meth:`poll` and :meth:`wait` (and indirectly |
| 708 | by :meth:`communicate`). A ``None`` value indicates that the process |
| 709 | hasn't terminated yet. |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 710 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 711 | A negative value ``-N`` indicates that the child was terminated by signal |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 712 | ``N`` (POSIX only). |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 713 | |
| 714 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 715 | Windows Popen Helpers |
| 716 | --------------------- |
| 717 | |
| 718 | The :class:`STARTUPINFO` class and following constants are only available |
| 719 | on Windows. |
| 720 | |
| 721 | .. class:: STARTUPINFO() |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 722 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 723 | Partial support of the Windows |
| 724 | `STARTUPINFO <http://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx>`__ |
| 725 | structure is used for :class:`Popen` creation. |
| 726 | |
| 727 | .. attribute:: dwFlags |
| 728 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 729 | A bit field that determines whether certain :class:`STARTUPINFO` |
| 730 | attributes are used when the process creates a window. :: |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 731 | |
| 732 | si = subprocess.STARTUPINFO() |
| 733 | si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW |
| 734 | |
| 735 | .. attribute:: hStdInput |
| 736 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 737 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 738 | is the standard input handle for the process. If |
| 739 | :data:`STARTF_USESTDHANDLES` is not specified, the default for standard |
| 740 | input is the keyboard buffer. |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 741 | |
| 742 | .. attribute:: hStdOutput |
| 743 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 744 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 745 | is the standard output handle for the process. Otherwise, this attribute |
| 746 | is ignored and the default for standard output is the console window's |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 747 | buffer. |
| 748 | |
| 749 | .. attribute:: hStdError |
| 750 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 751 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 752 | is the standard error handle for the process. Otherwise, this attribute is |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 753 | ignored and the default for standard error is the console window's buffer. |
| 754 | |
| 755 | .. attribute:: wShowWindow |
| 756 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 757 | If :attr:`dwFlags` specifies :data:`STARTF_USESHOWWINDOW`, this attribute |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 758 | can be any of the values that can be specified in the ``nCmdShow`` |
| 759 | parameter for the |
| 760 | `ShowWindow <http://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx>`__ |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 761 | function, except for ``SW_SHOWDEFAULT``. Otherwise, this attribute is |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 762 | ignored. |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 763 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 764 | :data:`SW_HIDE` is provided for this attribute. It is used when |
| 765 | :class:`Popen` is called with ``shell=True``. |
| 766 | |
| 767 | |
| 768 | Constants |
| 769 | ^^^^^^^^^ |
| 770 | |
| 771 | The :mod:`subprocess` module exposes the following constants. |
| 772 | |
| 773 | .. data:: STD_INPUT_HANDLE |
| 774 | |
| 775 | The standard input device. Initially, this is the console input buffer, |
| 776 | ``CONIN$``. |
| 777 | |
| 778 | .. data:: STD_OUTPUT_HANDLE |
| 779 | |
| 780 | The standard output device. Initially, this is the active console screen |
| 781 | buffer, ``CONOUT$``. |
| 782 | |
| 783 | .. data:: STD_ERROR_HANDLE |
| 784 | |
| 785 | The standard error device. Initially, this is the active console screen |
| 786 | buffer, ``CONOUT$``. |
| 787 | |
| 788 | .. data:: SW_HIDE |
| 789 | |
| 790 | Hides the window. Another window will be activated. |
| 791 | |
| 792 | .. data:: STARTF_USESTDHANDLES |
| 793 | |
| 794 | Specifies that the :attr:`STARTUPINFO.hStdInput`, |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 795 | :attr:`STARTUPINFO.hStdOutput`, and :attr:`STARTUPINFO.hStdError` attributes |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 796 | contain additional information. |
| 797 | |
| 798 | .. data:: STARTF_USESHOWWINDOW |
| 799 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 800 | Specifies that the :attr:`STARTUPINFO.wShowWindow` attribute contains |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 801 | additional information. |
| 802 | |
| 803 | .. data:: CREATE_NEW_CONSOLE |
| 804 | |
| 805 | The new process has a new console, instead of inheriting its parent's |
| 806 | console (the default). |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 807 | |
Brian Curtin | 3040193 | 2011-04-29 22:20:57 -0500 | [diff] [blame] | 808 | .. data:: CREATE_NEW_PROCESS_GROUP |
| 809 | |
| 810 | A :class:`Popen` ``creationflags`` parameter to specify that a new process |
| 811 | group will be created. This flag is necessary for using :func:`os.kill` |
| 812 | on the subprocess. |
| 813 | |
| 814 | This flag is ignored if :data:`CREATE_NEW_CONSOLE` is specified. |
| 815 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 816 | .. _call-function-trio: |
| 817 | |
| 818 | Older high-level API |
| 819 | -------------------- |
| 820 | |
| 821 | Prior to Python 3.5, these three functions comprised the high level API to |
| 822 | subprocess. You can now use :func:`run` in many cases, but lots of existing code |
| 823 | calls these functions. |
| 824 | |
| 825 | .. function:: call(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) |
| 826 | |
| 827 | Run the command described by *args*. Wait for command to complete, then |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 828 | return the :attr:`~Popen.returncode` attribute. |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 829 | |
| 830 | This is equivalent to:: |
| 831 | |
| 832 | run(...).returncode |
| 833 | |
| 834 | (except that the *input* and *check* parameters are not supported) |
| 835 | |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 836 | The arguments shown above are merely the most |
| 837 | common ones. The full function signature is largely the |
| 838 | same as that of the :class:`Popen` constructor - this function passes all |
| 839 | supplied arguments other than *timeout* directly through to that interface. |
| 840 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 841 | .. note:: |
| 842 | |
| 843 | Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this |
| 844 | function. The child process will block if it generates enough |
| 845 | output to a pipe to fill up the OS pipe buffer as the pipes are |
| 846 | not being read from. |
| 847 | |
| 848 | .. versionchanged:: 3.3 |
| 849 | *timeout* was added. |
| 850 | |
| 851 | .. function:: check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) |
| 852 | |
| 853 | Run command with arguments. Wait for command to complete. If the return |
| 854 | code was zero then return, otherwise raise :exc:`CalledProcessError`. The |
| 855 | :exc:`CalledProcessError` object will have the return code in the |
| 856 | :attr:`~CalledProcessError.returncode` attribute. |
| 857 | |
| 858 | This is equivalent to:: |
| 859 | |
| 860 | run(..., check=True) |
| 861 | |
| 862 | (except that the *input* parameter is not supported) |
| 863 | |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 864 | The arguments shown above are merely the most |
| 865 | common ones. The full function signature is largely the |
| 866 | same as that of the :class:`Popen` constructor - this function passes all |
| 867 | supplied arguments other than *timeout* directly through to that interface. |
| 868 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 869 | .. note:: |
| 870 | |
| 871 | Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this |
| 872 | function. The child process will block if it generates enough |
| 873 | output to a pipe to fill up the OS pipe buffer as the pipes are |
| 874 | not being read from. |
| 875 | |
| 876 | .. versionchanged:: 3.3 |
| 877 | *timeout* was added. |
| 878 | |
| 879 | |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 880 | .. function:: check_output(args, *, stdin=None, stderr=None, shell=False, universal_newlines=False, timeout=None) |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 881 | |
| 882 | Run command with arguments and return its output. |
| 883 | |
| 884 | If the return code was non-zero it raises a :exc:`CalledProcessError`. The |
| 885 | :exc:`CalledProcessError` object will have the return code in the |
| 886 | :attr:`~CalledProcessError.returncode` attribute and any output in the |
| 887 | :attr:`~CalledProcessError.output` attribute. |
| 888 | |
| 889 | This is equivalent to:: |
| 890 | |
| 891 | run(..., check=True, stdout=PIPE).stdout |
| 892 | |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 893 | The arguments shown above are merely the most common ones. |
| 894 | The full function signature is largely the same as that of :func:`run` - |
| 895 | most arguments are passed directly through to that interface. |
| 896 | However, explicitly passing ``input=None`` to inherit the parent's |
| 897 | standard input file handle is not supported. |
| 898 | |
Gregory P. Smith | 6e73000 | 2015-04-14 16:14:25 -0700 | [diff] [blame] | 899 | By default, this function will return the data as encoded bytes. The actual |
| 900 | encoding of the output data may depend on the command being invoked, so the |
| 901 | decoding to text will often need to be handled at the application level. |
| 902 | |
| 903 | This behaviour may be overridden by setting *universal_newlines* to |
| 904 | ``True`` as described above in :ref:`frequently-used-arguments`. |
| 905 | |
| 906 | To also capture standard error in the result, use |
| 907 | ``stderr=subprocess.STDOUT``:: |
| 908 | |
| 909 | >>> subprocess.check_output( |
| 910 | ... "ls non_existent_file; exit 0", |
| 911 | ... stderr=subprocess.STDOUT, |
| 912 | ... shell=True) |
| 913 | 'ls: non_existent_file: No such file or directory\n' |
| 914 | |
| 915 | .. versionadded:: 3.1 |
| 916 | |
| 917 | .. versionchanged:: 3.3 |
| 918 | *timeout* was added. |
| 919 | |
| 920 | .. versionchanged:: 3.4 |
Berker Peksag | bf1d4b6 | 2015-07-25 14:27:07 +0300 | [diff] [blame^] | 921 | Support for the *input* keyword argument was added. |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 922 | |
Benjamin Peterson | dcf97b9 | 2008-07-02 17:30:14 +0000 | [diff] [blame] | 923 | .. _subprocess-replacements: |
| 924 | |
Ezio Melotti | 402f75d | 2012-11-08 10:07:10 +0200 | [diff] [blame] | 925 | Replacing Older Functions with the :mod:`subprocess` Module |
| 926 | ----------------------------------------------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 927 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 928 | In this section, "a becomes b" means that b can be used as a replacement for a. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 929 | |
| 930 | .. note:: |
| 931 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 932 | All "a" functions in this section fail (more or less) silently if the |
| 933 | executed program cannot be found; the "b" replacements raise :exc:`OSError` |
| 934 | instead. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 935 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 936 | In addition, the replacements using :func:`check_output` will fail with a |
| 937 | :exc:`CalledProcessError` if the requested operation produces a non-zero |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 938 | return code. The output is still available as the |
| 939 | :attr:`~CalledProcessError.output` attribute of the raised exception. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 940 | |
| 941 | In the following examples, we assume that the relevant functions have already |
Ezio Melotti | 402f75d | 2012-11-08 10:07:10 +0200 | [diff] [blame] | 942 | been imported from the :mod:`subprocess` module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 943 | |
| 944 | |
| 945 | Replacing /bin/sh shell backquote |
| 946 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 947 | |
| 948 | :: |
| 949 | |
| 950 | output=`mycmd myarg` |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 951 | # becomes |
| 952 | output = check_output(["mycmd", "myarg"]) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 953 | |
| 954 | |
Benjamin Peterson | f10a79a | 2008-10-11 00:49:57 +0000 | [diff] [blame] | 955 | Replacing shell pipeline |
| 956 | ^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 957 | |
| 958 | :: |
| 959 | |
| 960 | output=`dmesg | grep hda` |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 961 | # becomes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 962 | p1 = Popen(["dmesg"], stdout=PIPE) |
| 963 | p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE) |
Gregory P. Smith | e09d2f1 | 2011-02-05 21:47:25 +0000 | [diff] [blame] | 964 | p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 965 | output = p2.communicate()[0] |
| 966 | |
Gregory P. Smith | e09d2f1 | 2011-02-05 21:47:25 +0000 | [diff] [blame] | 967 | The p1.stdout.close() call after starting the p2 is important in order for p1 |
| 968 | to receive a SIGPIPE if p2 exits before p1. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 969 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 970 | Alternatively, for trusted input, the shell's own pipeline support may still |
R David Murray | 28b8b94 | 2012-04-03 08:46:48 -0400 | [diff] [blame] | 971 | be used directly:: |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 972 | |
| 973 | output=`dmesg | grep hda` |
| 974 | # becomes |
| 975 | output=check_output("dmesg | grep hda", shell=True) |
| 976 | |
| 977 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 978 | Replacing :func:`os.system` |
| 979 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 980 | |
| 981 | :: |
| 982 | |
| 983 | sts = os.system("mycmd" + " myarg") |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 984 | # becomes |
| 985 | sts = call("mycmd" + " myarg", shell=True) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 986 | |
| 987 | Notes: |
| 988 | |
| 989 | * Calling the program through the shell is usually not required. |
| 990 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 991 | A more realistic example would look like this:: |
| 992 | |
| 993 | try: |
| 994 | retcode = call("mycmd" + " myarg", shell=True) |
| 995 | if retcode < 0: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 996 | print("Child was terminated by signal", -retcode, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 997 | else: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 998 | print("Child returned", retcode, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 999 | except OSError as e: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 1000 | print("Execution failed:", e, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1001 | |
| 1002 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1003 | Replacing the :func:`os.spawn <os.spawnl>` family |
| 1004 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1005 | |
| 1006 | P_NOWAIT example:: |
| 1007 | |
| 1008 | pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg") |
| 1009 | ==> |
| 1010 | pid = Popen(["/bin/mycmd", "myarg"]).pid |
| 1011 | |
| 1012 | P_WAIT example:: |
| 1013 | |
| 1014 | retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg") |
| 1015 | ==> |
| 1016 | retcode = call(["/bin/mycmd", "myarg"]) |
| 1017 | |
| 1018 | Vector example:: |
| 1019 | |
| 1020 | os.spawnvp(os.P_NOWAIT, path, args) |
| 1021 | ==> |
| 1022 | Popen([path] + args[1:]) |
| 1023 | |
| 1024 | Environment example:: |
| 1025 | |
| 1026 | os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env) |
| 1027 | ==> |
| 1028 | Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"}) |
| 1029 | |
| 1030 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1031 | |
| 1032 | Replacing :func:`os.popen`, :func:`os.popen2`, :func:`os.popen3` |
| 1033 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1034 | |
| 1035 | :: |
| 1036 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1037 | (child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1038 | ==> |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1039 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 1040 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 1041 | (child_stdin, child_stdout) = (p.stdin, p.stdout) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1042 | |
| 1043 | :: |
| 1044 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1045 | (child_stdin, |
| 1046 | child_stdout, |
| 1047 | child_stderr) = os.popen3(cmd, mode, bufsize) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1048 | ==> |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1049 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 1050 | stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True) |
| 1051 | (child_stdin, |
| 1052 | child_stdout, |
| 1053 | child_stderr) = (p.stdin, p.stdout, p.stderr) |
| 1054 | |
| 1055 | :: |
| 1056 | |
| 1057 | (child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize) |
| 1058 | ==> |
| 1059 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 1060 | stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True) |
| 1061 | (child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout) |
| 1062 | |
| 1063 | Return code handling translates as follows:: |
| 1064 | |
| 1065 | pipe = os.popen(cmd, 'w') |
| 1066 | ... |
| 1067 | rc = pipe.close() |
Stefan Krah | fc9e08d | 2010-07-14 10:16:11 +0000 | [diff] [blame] | 1068 | if rc is not None and rc >> 8: |
Ezio Melotti | 985e24d | 2009-09-13 07:54:02 +0000 | [diff] [blame] | 1069 | print("There were some errors") |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1070 | ==> |
| 1071 | process = Popen(cmd, 'w', stdin=PIPE) |
| 1072 | ... |
| 1073 | process.stdin.close() |
| 1074 | if process.wait() != 0: |
Ezio Melotti | 985e24d | 2009-09-13 07:54:02 +0000 | [diff] [blame] | 1075 | print("There were some errors") |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1076 | |
| 1077 | |
| 1078 | Replacing functions from the :mod:`popen2` module |
| 1079 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 1080 | |
| 1081 | .. note:: |
| 1082 | |
| 1083 | If the cmd argument to popen2 functions is a string, the command is executed |
| 1084 | through /bin/sh. If it is a list, the command is directly executed. |
| 1085 | |
| 1086 | :: |
| 1087 | |
| 1088 | (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode) |
| 1089 | ==> |
R David Murray | ae9d193 | 2014-05-14 10:09:52 -0400 | [diff] [blame] | 1090 | p = Popen("somestring", shell=True, bufsize=bufsize, |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1091 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 1092 | (child_stdout, child_stdin) = (p.stdout, p.stdin) |
| 1093 | |
| 1094 | :: |
| 1095 | |
| 1096 | (child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode) |
| 1097 | ==> |
| 1098 | p = Popen(["mycmd", "myarg"], bufsize=bufsize, |
| 1099 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 1100 | (child_stdout, child_stdin) = (p.stdout, p.stdin) |
| 1101 | |
| 1102 | :class:`popen2.Popen3` and :class:`popen2.Popen4` basically work as |
| 1103 | :class:`subprocess.Popen`, except that: |
| 1104 | |
| 1105 | * :class:`Popen` raises an exception if the execution fails. |
| 1106 | |
| 1107 | * the *capturestderr* argument is replaced with the *stderr* argument. |
| 1108 | |
| 1109 | * ``stdin=PIPE`` and ``stdout=PIPE`` must be specified. |
| 1110 | |
| 1111 | * popen2 closes all file descriptors by default, but you have to specify |
Gregory P. Smith | f560485 | 2010-12-13 06:45:02 +0000 | [diff] [blame] | 1112 | ``close_fds=True`` with :class:`Popen` to guarantee this behavior on |
| 1113 | all platforms or past Python versions. |
Eli Bendersky | 046a764 | 2011-04-15 07:23:26 +0300 | [diff] [blame] | 1114 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1115 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1116 | Legacy Shell Invocation Functions |
Nick Coghlan | 32e4a58 | 2011-11-08 21:50:58 +1000 | [diff] [blame] | 1117 | --------------------------------- |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1118 | |
| 1119 | This module also provides the following legacy functions from the 2.x |
| 1120 | ``commands`` module. These operations implicitly invoke the system shell and |
| 1121 | none of the guarantees described above regarding security and exception |
| 1122 | handling consistency are valid for these functions. |
| 1123 | |
| 1124 | .. function:: getstatusoutput(cmd) |
| 1125 | |
| 1126 | Return ``(status, output)`` of executing *cmd* in a shell. |
| 1127 | |
Tim Golden | 6079814 | 2013-11-05 12:57:25 +0000 | [diff] [blame] | 1128 | Execute the string *cmd* in a shell with :meth:`Popen.check_output` and |
| 1129 | return a 2-tuple ``(status, output)``. Universal newlines mode is used; |
| 1130 | see the notes on :ref:`frequently-used-arguments` for more details. |
Tim Golden | 3a2abb5 | 2013-11-03 18:24:50 +0000 | [diff] [blame] | 1131 | |
| 1132 | A trailing newline is stripped from the output. |
| 1133 | The exit status for the command can be interpreted |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1134 | according to the rules for the C function :c:func:`wait`. Example:: |
| 1135 | |
| 1136 | >>> subprocess.getstatusoutput('ls /bin/ls') |
| 1137 | (0, '/bin/ls') |
| 1138 | >>> subprocess.getstatusoutput('cat /bin/junk') |
| 1139 | (256, 'cat: /bin/junk: No such file or directory') |
| 1140 | >>> subprocess.getstatusoutput('/bin/junk') |
| 1141 | (256, 'sh: /bin/junk: not found') |
| 1142 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 1143 | Availability: POSIX & Windows |
R David Murray | 95b696a | 2014-03-07 20:04:17 -0500 | [diff] [blame] | 1144 | |
| 1145 | .. versionchanged:: 3.3.4 |
| 1146 | Windows support added |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1147 | |
| 1148 | |
| 1149 | .. function:: getoutput(cmd) |
| 1150 | |
| 1151 | Return output (stdout and stderr) of executing *cmd* in a shell. |
| 1152 | |
| 1153 | Like :func:`getstatusoutput`, except the exit status is ignored and the return |
| 1154 | value is a string containing the command's output. Example:: |
| 1155 | |
| 1156 | >>> subprocess.getoutput('ls /bin/ls') |
| 1157 | '/bin/ls' |
| 1158 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame] | 1159 | Availability: POSIX & Windows |
R David Murray | 95b696a | 2014-03-07 20:04:17 -0500 | [diff] [blame] | 1160 | |
| 1161 | .. versionchanged:: 3.3.4 |
| 1162 | Windows support added |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1163 | |
Nick Coghlan | 32e4a58 | 2011-11-08 21:50:58 +1000 | [diff] [blame] | 1164 | |
Eli Bendersky | 046a764 | 2011-04-15 07:23:26 +0300 | [diff] [blame] | 1165 | Notes |
| 1166 | ----- |
| 1167 | |
| 1168 | .. _converting-argument-sequence: |
| 1169 | |
| 1170 | Converting an argument sequence to a string on Windows |
| 1171 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 1172 | |
| 1173 | On Windows, an *args* sequence is converted to a string that can be parsed |
| 1174 | using the following rules (which correspond to the rules used by the MS C |
| 1175 | runtime): |
| 1176 | |
| 1177 | 1. Arguments are delimited by white space, which is either a |
| 1178 | space or a tab. |
| 1179 | |
| 1180 | 2. A string surrounded by double quotation marks is |
| 1181 | interpreted as a single argument, regardless of white space |
| 1182 | contained within. A quoted string can be embedded in an |
| 1183 | argument. |
| 1184 | |
| 1185 | 3. A double quotation mark preceded by a backslash is |
| 1186 | interpreted as a literal double quotation mark. |
| 1187 | |
| 1188 | 4. Backslashes are interpreted literally, unless they |
| 1189 | immediately precede a double quotation mark. |
| 1190 | |
| 1191 | 5. If backslashes immediately precede a double quotation mark, |
| 1192 | every pair of backslashes is interpreted as a literal |
| 1193 | backslash. If the number of backslashes is odd, the last |
| 1194 | backslash escapes the next double quotation mark as |
| 1195 | described in rule 3. |
| 1196 | |
Eli Bendersky | d211231 | 2011-04-15 07:26:28 +0300 | [diff] [blame] | 1197 | |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 1198 | .. seealso:: |
| 1199 | |
| 1200 | :mod:`shlex` |
| 1201 | Module which provides function to parse and escape command lines. |