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 | 21317b6 | 2014-03-12 21:42:04 -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 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 28 | The recommended approach to invoking subprocesses is to use the following |
| 29 | convenience functions for all use cases they can handle. For more advanced |
| 30 | use cases, the underlying :class:`Popen` interface can be used directly. |
| 31 | |
| 32 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 33 | .. function:: call(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 34 | |
| 35 | Run the command described by *args*. Wait for command to complete, then |
| 36 | return the :attr:`returncode` attribute. |
| 37 | |
| 38 | The arguments shown above are merely the most common ones, described below |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 39 | in :ref:`frequently-used-arguments` (hence the use of keyword-only notation |
| 40 | in the abbreviated signature). The full function signature is largely the |
| 41 | same as that of the :class:`Popen` constructor - this function passes all |
| 42 | supplied arguments other than *timeout* directly through to that interface. |
| 43 | |
| 44 | The *timeout* argument is passed to :meth:`Popen.wait`. If the timeout |
| 45 | expires, the child process will be killed and then waited for again. The |
| 46 | :exc:`TimeoutExpired` exception will be re-raised after the child process |
| 47 | has terminated. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 48 | |
| 49 | Examples:: |
| 50 | |
| 51 | >>> subprocess.call(["ls", "-l"]) |
| 52 | 0 |
| 53 | |
| 54 | >>> subprocess.call("exit 1", shell=True) |
| 55 | 1 |
| 56 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 57 | .. note:: |
| 58 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 59 | Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this |
| 60 | function. The child process will block if it generates enough |
| 61 | output to a pipe to fill up the OS pipe buffer as the pipes are |
| 62 | not being read from. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 63 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 64 | .. versionchanged:: 3.3 |
| 65 | *timeout* was added. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 66 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 67 | |
| 68 | .. function:: check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 69 | |
| 70 | Run command with arguments. Wait for command to complete. If the return |
| 71 | code was zero then return, otherwise raise :exc:`CalledProcessError`. The |
| 72 | :exc:`CalledProcessError` object will have the return code in the |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 73 | :attr:`~CalledProcessError.returncode` attribute. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 74 | |
| 75 | The arguments shown above are merely the most common ones, described below |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 76 | in :ref:`frequently-used-arguments` (hence the use of keyword-only notation |
| 77 | in the abbreviated signature). The full function signature is largely the |
| 78 | same as that of the :class:`Popen` constructor - this function passes all |
| 79 | supplied arguments other than *timeout* directly through to that interface. |
| 80 | |
| 81 | The *timeout* argument is passed to :meth:`Popen.wait`. If the timeout |
| 82 | expires, the child process will be killed and then waited for again. The |
| 83 | :exc:`TimeoutExpired` exception will be re-raised after the child process |
| 84 | has terminated. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 85 | |
| 86 | Examples:: |
| 87 | |
| 88 | >>> subprocess.check_call(["ls", "-l"]) |
| 89 | 0 |
| 90 | |
| 91 | >>> subprocess.check_call("exit 1", shell=True) |
| 92 | Traceback (most recent call last): |
| 93 | ... |
| 94 | subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 |
| 95 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 96 | .. note:: |
| 97 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 98 | Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this |
| 99 | function. The child process will block if it generates enough |
| 100 | output to a pipe to fill up the OS pipe buffer as the pipes are |
| 101 | not being read from. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 102 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 103 | .. versionchanged:: 3.3 |
| 104 | *timeout* was added. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 105 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 106 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 107 | .. function:: check_output(args, *, input=None, stdin=None, stderr=None, shell=False, universal_newlines=False, timeout=None) |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 108 | |
Gregory P. Smith | f16455a | 2013-03-19 23:36:31 -0700 | [diff] [blame] | 109 | Run command with arguments and return its output. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 110 | |
| 111 | If the return code was non-zero it raises a :exc:`CalledProcessError`. The |
| 112 | :exc:`CalledProcessError` object will have the return code in the |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 113 | :attr:`~CalledProcessError.returncode` attribute and any output in the |
| 114 | :attr:`~CalledProcessError.output` attribute. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 115 | |
| 116 | The arguments shown above are merely the most common ones, described below |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 117 | in :ref:`frequently-used-arguments` (hence the use of keyword-only notation |
| 118 | in the abbreviated signature). The full function signature is largely the |
| 119 | same as that of the :class:`Popen` constructor - this functions passes all |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 120 | supplied arguments other than *input* and *timeout* directly through to |
| 121 | that interface. In addition, *stdout* is not permitted as an argument, as |
| 122 | it is used internally to collect the output from the subprocess. |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 123 | |
| 124 | The *timeout* argument is passed to :meth:`Popen.wait`. If the timeout |
| 125 | expires, the child process will be killed and then waited for again. The |
| 126 | :exc:`TimeoutExpired` exception will be re-raised after the child process |
| 127 | has terminated. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 128 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 129 | The *input* argument is passed to :meth:`Popen.communicate` and thus to the |
| 130 | subprocess's stdin. If used it must be a byte sequence, or a string if |
| 131 | ``universal_newlines=True``. When used, the internal :class:`Popen` object |
| 132 | is automatically created with ``stdin=PIPE``, and the *stdin* argument may |
| 133 | not be used as well. |
| 134 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 135 | Examples:: |
| 136 | |
| 137 | >>> subprocess.check_output(["echo", "Hello World!"]) |
| 138 | b'Hello World!\n' |
| 139 | |
| 140 | >>> subprocess.check_output(["echo", "Hello World!"], universal_newlines=True) |
| 141 | 'Hello World!\n' |
| 142 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 143 | >>> subprocess.check_output(["sed", "-e", "s/foo/bar/"], |
| 144 | ... input=b"when in the course of fooman events\n") |
| 145 | b'when in the course of barman events\n' |
| 146 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 147 | >>> subprocess.check_output("exit 1", shell=True) |
| 148 | Traceback (most recent call last): |
| 149 | ... |
| 150 | subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 |
| 151 | |
| 152 | By default, this function will return the data as encoded bytes. The actual |
| 153 | encoding of the output data may depend on the command being invoked, so the |
| 154 | decoding to text will often need to be handled at the application level. |
| 155 | |
| 156 | This behaviour may be overridden by setting *universal_newlines* to |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 157 | ``True`` as described below in :ref:`frequently-used-arguments`. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 158 | |
| 159 | To also capture standard error in the result, use |
| 160 | ``stderr=subprocess.STDOUT``:: |
| 161 | |
| 162 | >>> subprocess.check_output( |
| 163 | ... "ls non_existent_file; exit 0", |
| 164 | ... stderr=subprocess.STDOUT, |
| 165 | ... shell=True) |
| 166 | 'ls: non_existent_file: No such file or directory\n' |
| 167 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 168 | .. note:: |
| 169 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 170 | Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this |
| 171 | function. The child process will block if it generates enough |
| 172 | output to a pipe to fill up the OS pipe buffer as the pipes are |
| 173 | not being read from. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 174 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 175 | .. versionadded:: 3.1 |
| 176 | |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 177 | .. versionchanged:: 3.3 |
| 178 | *timeout* was added. |
| 179 | |
Serhiy Storchaka | fcd9f22 | 2013-04-22 20:20:54 +0300 | [diff] [blame] | 180 | .. versionchanged:: 3.4 |
| 181 | *input* was added. |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 182 | |
| 183 | .. data:: DEVNULL |
| 184 | |
| 185 | Special value that can be used as the *stdin*, *stdout* or *stderr* argument |
| 186 | to :class:`Popen` and indicates that the special file :data:`os.devnull` |
| 187 | will be used. |
| 188 | |
| 189 | .. versionadded:: 3.3 |
| 190 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 191 | |
| 192 | .. data:: PIPE |
| 193 | |
| 194 | Special value that can be used as the *stdin*, *stdout* or *stderr* argument |
| 195 | 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] | 196 | opened. Most useful with :meth:`Popen.communicate`. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 197 | |
| 198 | |
| 199 | .. data:: STDOUT |
| 200 | |
| 201 | Special value that can be used as the *stderr* argument to :class:`Popen` and |
| 202 | indicates that standard error should go into the same handle as standard |
| 203 | output. |
| 204 | |
| 205 | |
Andrew Svetlov | b4a09ab | 2012-08-09 15:11:45 +0300 | [diff] [blame] | 206 | .. exception:: SubprocessError |
| 207 | |
| 208 | Base class for all other exceptions from this module. |
| 209 | |
| 210 | .. versionadded:: 3.3 |
| 211 | |
| 212 | |
| 213 | .. exception:: TimeoutExpired |
| 214 | |
| 215 | Subclass of :exc:`SubprocessError`, raised when a timeout expires |
| 216 | while waiting for a child process. |
| 217 | |
| 218 | .. attribute:: cmd |
| 219 | |
| 220 | Command that was used to spawn the child process. |
| 221 | |
| 222 | .. attribute:: timeout |
| 223 | |
| 224 | Timeout in seconds. |
| 225 | |
| 226 | .. attribute:: output |
| 227 | |
| 228 | Output of the child process if this exception is raised by |
| 229 | :func:`check_output`. Otherwise, ``None``. |
| 230 | |
| 231 | .. versionadded:: 3.3 |
| 232 | |
| 233 | |
| 234 | .. exception:: CalledProcessError |
| 235 | |
| 236 | Subclass of :exc:`SubprocessError`, raised when a process run by |
| 237 | :func:`check_call` or :func:`check_output` returns a non-zero exit status. |
| 238 | |
| 239 | .. attribute:: returncode |
| 240 | |
| 241 | Exit status of the child process. |
| 242 | |
| 243 | .. attribute:: cmd |
| 244 | |
| 245 | Command that was used to spawn the child process. |
| 246 | |
| 247 | .. attribute:: output |
| 248 | |
| 249 | Output of the child process if this exception is raised by |
| 250 | :func:`check_output`. Otherwise, ``None``. |
| 251 | |
| 252 | |
| 253 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 254 | .. _frequently-used-arguments: |
| 255 | |
| 256 | Frequently Used Arguments |
| 257 | ^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 258 | |
| 259 | To support a wide variety of use cases, the :class:`Popen` constructor (and |
| 260 | the convenience functions) accept a large number of optional arguments. For |
| 261 | most typical use cases, many of these arguments can be safely left at their |
| 262 | default values. The arguments that are most commonly needed are: |
| 263 | |
| 264 | *args* is required for all calls and should be a string, or a sequence of |
| 265 | program arguments. Providing a sequence of arguments is generally |
| 266 | preferred, as it allows the module to take care of any required escaping |
| 267 | and quoting of arguments (e.g. to permit spaces in file names). If passing |
| 268 | a single string, either *shell* must be :const:`True` (see below) or else |
| 269 | the string must simply name the program to be executed without specifying |
| 270 | any arguments. |
| 271 | |
| 272 | *stdin*, *stdout* and *stderr* specify the executed program's standard input, |
| 273 | standard output and standard error file handles, respectively. Valid values |
Nick Coghlan | 217f05b | 2011-11-08 22:11:21 +1000 | [diff] [blame] | 274 | are :data:`PIPE`, :data:`DEVNULL`, an existing file descriptor (a positive |
| 275 | integer), an existing file object, and ``None``. :data:`PIPE` indicates |
| 276 | that a new pipe to the child should be created. :data:`DEVNULL` indicates |
| 277 | that the special file :data:`os.devnull` will be used. With the default |
| 278 | settings of ``None``, no redirection will occur; the child's file handles |
| 279 | will be inherited from the parent. Additionally, *stderr* can be |
| 280 | :data:`STDOUT`, which indicates that the stderr data from the child |
| 281 | process should be captured into the same file handle as for *stdout*. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 282 | |
R David Murray | 1b00f25 | 2012-08-15 10:43:58 -0400 | [diff] [blame] | 283 | .. index:: |
| 284 | single: universal newlines; subprocess module |
| 285 | |
Ronald Oussoren | 385521c | 2013-07-07 09:26:45 +0200 | [diff] [blame] | 286 | If *universal_newlines* is ``False`` the file objects *stdin*, *stdout* and |
| 287 | *stderr* will be opened as binary streams, and no line ending conversion is |
| 288 | done. |
| 289 | |
| 290 | If *universal_newlines* is ``True``, these file objects |
| 291 | will be opened as text streams in :term:`universal newlines` mode |
R David Murray | 0689ce4 | 2012-08-15 11:13:31 -0400 | [diff] [blame] | 292 | using the encoding returned by :func:`locale.getpreferredencoding(False) |
Ronald Oussoren | 385521c | 2013-07-07 09:26:45 +0200 | [diff] [blame] | 293 | <locale.getpreferredencoding>`. For *stdin*, line ending characters |
R David Murray | 0689ce4 | 2012-08-15 11:13:31 -0400 | [diff] [blame] | 294 | ``'\n'`` in the input will be converted to the default line separator |
| 295 | :data:`os.linesep`. For *stdout* and *stderr*, all line endings in the |
| 296 | output will be converted to ``'\n'``. For more information see the |
| 297 | documentation of the :class:`io.TextIOWrapper` class when the *newline* |
| 298 | argument to its constructor is ``None``. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 299 | |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 300 | .. note:: |
| 301 | |
Gregory P. Smith | 1f8a40b | 2013-03-20 18:32:03 -0700 | [diff] [blame] | 302 | The newlines attribute of the file objects :attr:`Popen.stdin`, |
| 303 | :attr:`Popen.stdout` and :attr:`Popen.stderr` are not updated by |
| 304 | the :meth:`Popen.communicate` method. |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 305 | |
| 306 | If *shell* is ``True``, the specified command will be executed through |
Ezio Melotti | 186d523 | 2012-09-15 08:34:08 +0300 | [diff] [blame] | 307 | 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] | 308 | enhanced control flow it offers over most system shells and still want |
Ezio Melotti | 186d523 | 2012-09-15 08:34:08 +0300 | [diff] [blame] | 309 | convenient access to other shell features such as shell pipes, filename |
| 310 | wildcards, environment variable expansion, and expansion of ``~`` to a |
| 311 | user's home directory. However, note that Python itself offers |
| 312 | implementations of many shell-like features (in particular, :mod:`glob`, |
| 313 | :mod:`fnmatch`, :func:`os.walk`, :func:`os.path.expandvars`, |
| 314 | :func:`os.path.expanduser`, and :mod:`shutil`). |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 315 | |
Andrew Svetlov | 4805fa8 | 2012-08-13 22:11:14 +0300 | [diff] [blame] | 316 | .. versionchanged:: 3.3 |
| 317 | When *universal_newlines* is ``True``, the class uses the encoding |
| 318 | :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>` |
| 319 | instead of ``locale.getpreferredencoding()``. See the |
| 320 | :class:`io.TextIOWrapper` class for more information on this change. |
| 321 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 322 | .. note:: |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 323 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 324 | Read the `Security Considerations`_ section before using ``shell=True``. |
Andrew Svetlov | c2415eb | 2012-10-28 11:42:26 +0200 | [diff] [blame] | 325 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 326 | These options, along with all of the other options, are described in more |
| 327 | detail in the :class:`Popen` constructor documentation. |
| 328 | |
| 329 | |
Sandro Tosi | 1526ad1 | 2011-12-25 11:27:37 +0100 | [diff] [blame] | 330 | Popen Constructor |
Sandro Tosi | 3e6c814 | 2011-12-25 17:14:11 +0100 | [diff] [blame] | 331 | ^^^^^^^^^^^^^^^^^ |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 332 | |
| 333 | The underlying process creation and management in this module is handled by |
| 334 | the :class:`Popen` class. It offers a lot of flexibility so that developers |
| 335 | are able to handle the less common cases not covered by the convenience |
| 336 | functions. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 337 | |
| 338 | |
Gregory P. Smith | a1ed539 | 2013-03-23 11:44:25 -0700 | [diff] [blame] | 339 | .. class:: Popen(args, bufsize=-1, executable=None, stdin=None, stdout=None, \ |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 340 | stderr=None, preexec_fn=None, close_fds=True, shell=False, \ |
| 341 | cwd=None, env=None, universal_newlines=False, \ |
| 342 | startupinfo=None, creationflags=0, restore_signals=True, \ |
| 343 | start_new_session=False, pass_fds=()) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 344 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 345 | 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] | 346 | :meth:`os.execvp`-like behavior to execute the child program. On Windows, |
| 347 | the class uses the Windows ``CreateProcess()`` function. The arguments to |
| 348 | :class:`Popen` are as follows. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 349 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 350 | *args* should be a sequence of program arguments or else a single string. |
| 351 | 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] | 352 | a sequence. If *args* is a string, the interpretation is |
| 353 | platform-dependent and described below. See the *shell* and *executable* |
| 354 | arguments for additional differences from the default behavior. Unless |
| 355 | otherwise stated, it is recommended to pass *args* as a sequence. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 356 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 357 | 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] | 358 | path of the program to execute. However, this can only be done if not |
| 359 | passing arguments to the program. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 360 | |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 361 | .. note:: |
| 362 | |
| 363 | :meth:`shlex.split` can be useful when determining the correct |
| 364 | tokenization for *args*, especially in complex cases:: |
| 365 | |
| 366 | >>> import shlex, subprocess |
R. David Murray | 73bc75b | 2010-02-05 16:25:12 +0000 | [diff] [blame] | 367 | >>> command_line = input() |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 368 | /bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'" |
| 369 | >>> args = shlex.split(command_line) |
| 370 | >>> print(args) |
| 371 | ['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"] |
| 372 | >>> p = subprocess.Popen(args) # Success! |
| 373 | |
| 374 | Note in particular that options (such as *-input*) and arguments (such |
| 375 | as *eggs.txt*) that are separated by whitespace in the shell go in separate |
| 376 | list elements, while arguments that need quoting or backslash escaping when |
| 377 | used in the shell (such as filenames containing spaces or the *echo* command |
| 378 | shown above) are single list elements. |
| 379 | |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 380 | On Windows, if *args* is a sequence, it will be converted to a string in a |
| 381 | manner described in :ref:`converting-argument-sequence`. This is because |
| 382 | the underlying ``CreateProcess()`` operates on strings. |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 383 | |
| 384 | The *shell* argument (which defaults to *False*) specifies whether to use |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 385 | the shell as the program to execute. If *shell* is *True*, it is |
| 386 | recommended to pass *args* as a string rather than as a sequence. |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 387 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 388 | 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] | 389 | *args* is a string, the string specifies the command |
| 390 | 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] | 391 | formatted exactly as it would be when typed at the shell prompt. This |
| 392 | includes, for example, quoting or backslash escaping filenames with spaces in |
| 393 | them. If *args* is a sequence, the first item specifies the command string, and |
| 394 | any additional items will be treated as additional arguments to the shell |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 395 | itself. That is to say, :class:`Popen` does the equivalent of:: |
R. David Murray | 5973e4d | 2010-02-04 16:41:57 +0000 | [diff] [blame] | 396 | |
| 397 | Popen(['/bin/sh', '-c', args[0], args[1], ...]) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 398 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 399 | On Windows with ``shell=True``, the :envvar:`COMSPEC` environment variable |
| 400 | specifies the default shell. The only time you need to specify |
| 401 | ``shell=True`` on Windows is when the command you wish to execute is built |
| 402 | into the shell (e.g. :command:`dir` or :command:`copy`). You do not need |
| 403 | ``shell=True`` to run a batch file or console-based executable. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 404 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 405 | .. note:: |
Chris Jerdonek | cc32a68 | 2012-10-10 22:52:22 -0700 | [diff] [blame] | 406 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 407 | Read the `Security Considerations`_ section before using ``shell=True``. |
Chris Jerdonek | cc32a68 | 2012-10-10 22:52:22 -0700 | [diff] [blame] | 408 | |
Benjamin Peterson | eacec1c | 2014-01-18 00:47:00 -0500 | [diff] [blame] | 409 | *bufsize* will be supplied as the corresponding argument to the :func:`open` |
| 410 | function when creating the stdin/stdout/stderr pipe file objects: :const:`0` |
| 411 | means unbuffered (read and write are one system call and can return short), |
| 412 | :const:`1` means line buffered, any other positive value means use a buffer |
| 413 | of approximately that size. A negative bufsize (the default) means the |
| 414 | system default of io.DEFAULT_BUFFER_SIZE will be used. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 415 | |
Georg Brandl | 37b70bb | 2013-11-25 08:48:37 +0100 | [diff] [blame] | 416 | .. versionchanged:: 3.3.1 |
Gregory P. Smith | a1ed539 | 2013-03-23 11:44:25 -0700 | [diff] [blame] | 417 | *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] | 418 | behavior that most code expects. In versions prior to Python 3.2.4 and |
| 419 | 3.3.1 it incorrectly defaulted to :const:`0` which was unbuffered |
| 420 | and allowed short reads. This was unintentional and did not match the |
| 421 | behavior of Python 2 as most code expected. |
Antoine Pitrou | 4b87620 | 2010-06-02 17:10:49 +0000 | [diff] [blame] | 422 | |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 423 | The *executable* argument specifies a replacement program to execute. It |
| 424 | is very seldom needed. When ``shell=False``, *executable* replaces the |
Chris Jerdonek | 4a4a02b | 2012-10-10 17:46:18 -0700 | [diff] [blame] | 425 | program to execute specified by *args*. However, the original *args* is |
| 426 | still passed to the program. Most programs treat the program specified |
| 427 | 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^] | 428 | actually executed. On POSIX, the *args* name |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 429 | becomes the display name for the executable in utilities such as |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 430 | :program:`ps`. If ``shell=True``, on POSIX the *executable* argument |
Chris Jerdonek | 470ee39 | 2012-10-08 23:06:57 -0700 | [diff] [blame] | 431 | specifies a replacement shell for the default :file:`/bin/sh`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 432 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 433 | *stdin*, *stdout* and *stderr* specify the executed program's standard input, |
Georg Brandl | af265f4 | 2008-12-07 15:06:20 +0000 | [diff] [blame] | 434 | standard output and standard error file handles, respectively. Valid values |
Ross Lagerwall | ba102ec | 2011-03-16 18:40:25 +0200 | [diff] [blame] | 435 | are :data:`PIPE`, :data:`DEVNULL`, an existing file descriptor (a positive |
| 436 | integer), an existing :term:`file object`, and ``None``. :data:`PIPE` |
| 437 | 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] | 438 | indicates that the special file :data:`os.devnull` will be used. With the |
| 439 | default settings of ``None``, no redirection will occur; the child's file |
| 440 | handles will be inherited from the parent. Additionally, *stderr* can be |
| 441 | :data:`STDOUT`, which indicates that the stderr data from the applications |
| 442 | should be captured into the same file handle as for stdout. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 443 | |
| 444 | 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] | 445 | child process just before the child is executed. |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 446 | (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 447 | |
| 448 | .. warning:: |
| 449 | |
| 450 | The *preexec_fn* parameter is not safe to use in the presence of threads |
| 451 | in your application. The child process could deadlock before exec is |
| 452 | called. |
| 453 | If you must use it, keep it trivial! Minimize the number of libraries |
| 454 | you call into. |
| 455 | |
| 456 | .. note:: |
| 457 | |
| 458 | If you need to modify the environment for the child use the *env* |
| 459 | parameter rather than doing it in a *preexec_fn*. |
| 460 | The *start_new_session* parameter can take the place of a previously |
| 461 | common use of *preexec_fn* to call os.setsid() in the child. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 462 | |
| 463 | 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^] | 464 | :const:`2` will be closed before the child process is executed. (POSIX only). |
| 465 | 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] | 466 | true when *stdin*/*stdout*/*stderr* are :const:`None`, false otherwise. |
Gregory P. Smith | d23047b | 2010-12-04 09:10:44 +0000 | [diff] [blame] | 467 | 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] | 468 | child process. Note that on Windows, you cannot set *close_fds* to true and |
| 469 | also redirect the standard handles by setting *stdin*, *stdout* or *stderr*. |
| 470 | |
Gregory P. Smith | 8edd99d | 2010-12-14 13:43:30 +0000 | [diff] [blame] | 471 | .. versionchanged:: 3.2 |
| 472 | The default for *close_fds* was changed from :const:`False` to |
| 473 | what is described above. |
| 474 | |
| 475 | *pass_fds* is an optional sequence of file descriptors to keep open |
| 476 | between the parent and child. Providing any *pass_fds* forces |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 477 | *close_fds* to be :const:`True`. (POSIX only) |
Gregory P. Smith | 8edd99d | 2010-12-14 13:43:30 +0000 | [diff] [blame] | 478 | |
| 479 | .. versionadded:: 3.2 |
| 480 | The *pass_fds* parameter was added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 481 | |
Chris Jerdonek | ec3ea94 | 2012-09-30 00:10:28 -0700 | [diff] [blame] | 482 | If *cwd* is not ``None``, the function changes the working directory to |
| 483 | *cwd* before executing the child. In particular, the function looks for |
| 484 | *executable* (or for the first item in *args*) relative to *cwd* if the |
| 485 | executable path is a relative path. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 486 | |
Serhiy Storchaka | fbc1c26 | 2013-11-29 12:17:13 +0200 | [diff] [blame] | 487 | 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] | 488 | SIG_IGN are restored to SIG_DFL in the child process before the exec. |
| 489 | Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 490 | (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 491 | |
| 492 | .. versionchanged:: 3.2 |
| 493 | *restore_signals* was added. |
| 494 | |
Serhiy Storchaka | fbc1c26 | 2013-11-29 12:17:13 +0200 | [diff] [blame] | 495 | 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^] | 496 | child process prior to the execution of the subprocess. (POSIX only) |
Gregory P. Smith | fb94c5f | 2010-03-14 06:49:55 +0000 | [diff] [blame] | 497 | |
| 498 | .. versionchanged:: 3.2 |
| 499 | *start_new_session* was added. |
| 500 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 501 | 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] | 502 | variables for the new process; these are used instead of the default |
| 503 | behavior of inheriting the current process' environment. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 504 | |
R. David Murray | 1055e89 | 2009-04-16 18:15:32 +0000 | [diff] [blame] | 505 | .. note:: |
R. David Murray | f4ac149 | 2009-04-15 22:35:15 +0000 | [diff] [blame] | 506 | |
Georg Brandl | 2708f3a | 2009-12-20 14:38:23 +0000 | [diff] [blame] | 507 | If specified, *env* must provide any variables required for the program to |
| 508 | execute. On Windows, in order to run a `side-by-side assembly`_ the |
| 509 | specified *env* **must** include a valid :envvar:`SystemRoot`. |
R. David Murray | f4ac149 | 2009-04-15 22:35:15 +0000 | [diff] [blame] | 510 | |
R. David Murray | 1055e89 | 2009-04-16 18:15:32 +0000 | [diff] [blame] | 511 | .. _side-by-side assembly: http://en.wikipedia.org/wiki/Side-by-Side_Assembly |
| 512 | |
Andrew Svetlov | 50be452 | 2012-08-13 22:09:04 +0300 | [diff] [blame] | 513 | If *universal_newlines* is ``True``, the file objects *stdin*, *stdout* |
R David Murray | 1b00f25 | 2012-08-15 10:43:58 -0400 | [diff] [blame] | 514 | and *stderr* are opened as text streams in universal newlines mode, as |
Ronald Oussoren | a686505 | 2013-07-06 10:23:59 +0200 | [diff] [blame] | 515 | described above in :ref:`frequently-used-arguments`, otherwise they are |
| 516 | opened as binary streams. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 517 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 518 | If given, *startupinfo* will be a :class:`STARTUPINFO` object, which is |
| 519 | passed to the underlying ``CreateProcess`` function. |
Brian Curtin | 3040193 | 2011-04-29 22:20:57 -0500 | [diff] [blame] | 520 | *creationflags*, if given, can be :data:`CREATE_NEW_CONSOLE` or |
| 521 | :data:`CREATE_NEW_PROCESS_GROUP`. (Windows only) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 522 | |
Gregory P. Smith | 6b65745 | 2011-05-11 21:42:08 -0700 | [diff] [blame] | 523 | Popen objects are supported as context managers via the :keyword:`with` statement: |
| 524 | 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] | 525 | :: |
| 526 | |
| 527 | with Popen(["ifconfig"], stdout=PIPE) as proc: |
| 528 | log.write(proc.stdout.read()) |
| 529 | |
| 530 | .. versionchanged:: 3.2 |
| 531 | Added context manager support. |
| 532 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 533 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 534 | Exceptions |
| 535 | ^^^^^^^^^^ |
| 536 | |
| 537 | Exceptions raised in the child process, before the new program has started to |
| 538 | execute, will be re-raised in the parent. Additionally, the exception object |
| 539 | 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] | 540 | containing traceback information from the child's point of view. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 541 | |
| 542 | The most common exception raised is :exc:`OSError`. This occurs, for example, |
| 543 | when trying to execute a non-existent file. Applications should prepare for |
| 544 | :exc:`OSError` exceptions. |
| 545 | |
| 546 | A :exc:`ValueError` will be raised if :class:`Popen` is called with invalid |
| 547 | arguments. |
| 548 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 549 | :func:`check_call` and :func:`check_output` will raise |
| 550 | :exc:`CalledProcessError` if the called process returns a non-zero return |
| 551 | code. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 552 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 553 | All of the functions and methods that accept a *timeout* parameter, such as |
| 554 | :func:`call` and :meth:`Popen.communicate` will raise :exc:`TimeoutExpired` if |
| 555 | the timeout expires before the process exits. |
| 556 | |
Ronald Oussoren | c157790 | 2011-03-16 10:03:10 -0400 | [diff] [blame] | 557 | Exceptions defined in this module all inherit from :exc:`SubprocessError`. |
Gregory P. Smith | 54d412e | 2011-03-14 14:08:43 -0400 | [diff] [blame] | 558 | |
| 559 | .. versionadded:: 3.3 |
| 560 | The :exc:`SubprocessError` base class was added. |
| 561 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 562 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 563 | Security Considerations |
| 564 | ----------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 565 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 566 | Unlike some other popen functions, this implementation will never |
| 567 | implicitly call a system shell. This means that all characters, |
| 568 | including shell metacharacters, can safely be passed to child processes. |
| 569 | If the shell is invoked explicitly, via ``shell=True``, it is the application's |
| 570 | responsibility to ensure that all whitespace and metacharacters are |
| 571 | quoted appropriately to avoid |
| 572 | `shell injection <http://en.wikipedia.org/wiki/Shell_injection#Shell_injection>`_ |
| 573 | vulnerabilities. |
| 574 | |
| 575 | When using ``shell=True``, the :func:`shlex.quote` function can be |
| 576 | used to properly escape whitespace and shell metacharacters in strings |
| 577 | that are going to be used to construct shell commands. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 578 | |
| 579 | |
| 580 | Popen Objects |
| 581 | ------------- |
| 582 | |
| 583 | Instances of the :class:`Popen` class have the following methods: |
| 584 | |
| 585 | |
| 586 | .. method:: Popen.poll() |
| 587 | |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 588 | Check if child process has terminated. Set and return |
| 589 | :attr:`~Popen.returncode` attribute. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 590 | |
| 591 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 592 | .. method:: Popen.wait(timeout=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 593 | |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 594 | Wait for child process to terminate. Set and return |
| 595 | :attr:`~Popen.returncode` attribute. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 596 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 597 | If the process does not terminate after *timeout* seconds, raise a |
| 598 | :exc:`TimeoutExpired` exception. It is safe to catch this exception and |
| 599 | retry the wait. |
| 600 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 601 | .. note:: |
| 602 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 603 | This will deadlock when using ``stdout=PIPE`` or ``stderr=PIPE`` |
| 604 | and the child process generates enough output to a pipe such that |
| 605 | it blocks waiting for the OS pipe buffer to accept more data. |
| 606 | Use :meth:`Popen.communicate` when using pipes to avoid that. |
| 607 | |
| 608 | .. note:: |
| 609 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 610 | The function is implemented using a busy loop (non-blocking call and |
| 611 | short sleeps). Use the :mod:`asyncio` module for an asynchronous wait: |
| 612 | see :class:`asyncio.create_subprocess_exec`. |
| 613 | |
Reid Kleckner | 28f1303 | 2011-03-14 12:36:53 -0400 | [diff] [blame] | 614 | .. versionchanged:: 3.3 |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 615 | *timeout* was added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 616 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 617 | .. deprecated:: 3.4 |
| 618 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 619 | Do not use the *endtime* parameter. It is was unintentionally |
| 620 | exposed in 3.3 but was left undocumented as it was intended to be |
| 621 | private for internal use. Use *timeout* instead. |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 622 | |
| 623 | .. method:: Popen.communicate(input=None, timeout=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 624 | |
| 625 | 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] | 626 | 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] | 627 | *input* argument should be data to be sent to the child process, or |
| 628 | ``None``, if no data should be sent to the child. The type of *input* |
| 629 | must be bytes or, if *universal_newlines* was ``True``, a string. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 630 | |
Georg Brandl | af265f4 | 2008-12-07 15:06:20 +0000 | [diff] [blame] | 631 | :meth:`communicate` returns a tuple ``(stdoutdata, stderrdata)``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 632 | |
Guido van Rossum | 0d3fb8a | 2007-11-26 23:23:18 +0000 | [diff] [blame] | 633 | Note that if you want to send data to the process's stdin, you need to create |
| 634 | the Popen object with ``stdin=PIPE``. Similarly, to get anything other than |
| 635 | ``None`` in the result tuple, you need to give ``stdout=PIPE`` and/or |
| 636 | ``stderr=PIPE`` too. |
| 637 | |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 638 | If the process does not terminate after *timeout* seconds, a |
| 639 | :exc:`TimeoutExpired` exception will be raised. Catching this exception and |
| 640 | retrying communication will not lose any output. |
| 641 | |
| 642 | The child process is not killed if the timeout expires, so in order to |
| 643 | cleanup properly a well-behaved application should kill the child process and |
| 644 | finish communication:: |
| 645 | |
| 646 | proc = subprocess.Popen(...) |
| 647 | try: |
| 648 | outs, errs = proc.communicate(timeout=15) |
| 649 | except TimeoutExpired: |
| 650 | proc.kill() |
| 651 | outs, errs = proc.communicate() |
| 652 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 653 | .. note:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 654 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 655 | The data read is buffered in memory, so do not use this method if the data |
| 656 | size is large or unlimited. |
| 657 | |
Reid Kleckner | 28f1303 | 2011-03-14 12:36:53 -0400 | [diff] [blame] | 658 | .. versionchanged:: 3.3 |
Reid Kleckner | 31aa7dd | 2011-03-14 12:02:10 -0400 | [diff] [blame] | 659 | *timeout* was added. |
| 660 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 661 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 662 | .. method:: Popen.send_signal(signal) |
| 663 | |
| 664 | Sends the signal *signal* to the child. |
| 665 | |
| 666 | .. note:: |
| 667 | |
Brian Curtin | eb24d74 | 2010-04-12 17:16:38 +0000 | [diff] [blame] | 668 | 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] | 669 | CTRL_BREAK_EVENT can be sent to processes started with a *creationflags* |
Brian Curtin | eb24d74 | 2010-04-12 17:16:38 +0000 | [diff] [blame] | 670 | parameter which includes `CREATE_NEW_PROCESS_GROUP`. |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 671 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 672 | |
| 673 | .. method:: Popen.terminate() |
| 674 | |
| 675 | Stop the child. On Posix OSs the method sends SIGTERM to the |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 676 | child. On Windows the Win32 API function :c:func:`TerminateProcess` is called |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 677 | to stop the child. |
| 678 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 679 | |
| 680 | .. method:: Popen.kill() |
| 681 | |
| 682 | Kills the child. On Posix OSs the function sends SIGKILL to the child. |
| 683 | On Windows :meth:`kill` is an alias for :meth:`terminate`. |
| 684 | |
Christian Heimes | a342c01 | 2008-04-20 21:01:16 +0000 | [diff] [blame] | 685 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 686 | The following attributes are also available: |
| 687 | |
Gregory P. Smith | 024c5ee | 2014-04-29 11:33:23 -0700 | [diff] [blame] | 688 | .. attribute:: Popen.args |
| 689 | |
| 690 | The *args* argument as it was passed to :class:`Popen` -- a |
| 691 | sequence of program arguments or else a single string. |
| 692 | |
| 693 | .. versionadded:: 3.3 |
Georg Brandl | 734e268 | 2008-08-12 08:18:18 +0000 | [diff] [blame] | 694 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 695 | .. attribute:: Popen.stdin |
| 696 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 697 | If the *stdin* argument was :data:`PIPE`, this attribute is a writeable |
| 698 | stream object as returned by :func:`open`. If the *universal_newlines* |
| 699 | argument was ``True``, the stream is a text stream, otherwise it is a byte |
| 700 | stream. If the *stdin* argument was not :data:`PIPE`, this attribute is |
| 701 | ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 702 | |
| 703 | |
| 704 | .. attribute:: Popen.stdout |
| 705 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 706 | If the *stdout* argument was :data:`PIPE`, this attribute is a readable |
| 707 | stream object as returned by :func:`open`. Reading from the stream provides |
| 708 | output from the child process. If the *universal_newlines* argument was |
| 709 | ``True``, the stream is a text stream, otherwise it is a byte stream. If the |
| 710 | *stdout* argument was not :data:`PIPE`, this attribute is ``None``. |
Benjamin Peterson | af69fe2 | 2014-01-18 00:49:04 -0500 | [diff] [blame] | 711 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 712 | |
| 713 | .. attribute:: Popen.stderr |
| 714 | |
Benjamin Peterson | 3d8814e | 2014-01-18 00:45:56 -0500 | [diff] [blame] | 715 | If the *stderr* argument was :data:`PIPE`, this attribute is a readable |
| 716 | stream object as returned by :func:`open`. Reading from the stream provides |
| 717 | error output from the child process. If the *universal_newlines* argument was |
| 718 | ``True``, the stream is a text stream, otherwise it is a byte stream. If the |
| 719 | *stderr* argument was not :data:`PIPE`, this attribute is ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 720 | |
Gregory P. Smith | 6436cba | 2014-05-11 13:26:21 -0700 | [diff] [blame] | 721 | .. warning:: |
| 722 | |
| 723 | Use :meth:`~Popen.communicate` rather than :attr:`.stdin.write <Popen.stdin>`, |
| 724 | :attr:`.stdout.read <Popen.stdout>` or :attr:`.stderr.read <Popen.stderr>` to avoid |
| 725 | deadlocks due to any of the other OS pipe buffers filling up and blocking the |
| 726 | child process. |
| 727 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 728 | |
| 729 | .. attribute:: Popen.pid |
| 730 | |
| 731 | The process ID of the child process. |
| 732 | |
Georg Brandl | 58bfdca | 2010-03-21 09:50:49 +0000 | [diff] [blame] | 733 | Note that if you set the *shell* argument to ``True``, this is the process ID |
| 734 | of the spawned shell. |
| 735 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 736 | |
| 737 | .. attribute:: Popen.returncode |
| 738 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 739 | The child return code, set by :meth:`poll` and :meth:`wait` (and indirectly |
| 740 | by :meth:`communicate`). A ``None`` value indicates that the process |
| 741 | hasn't terminated yet. |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 742 | |
Christian Heimes | 7f04431 | 2008-01-06 17:05:40 +0000 | [diff] [blame] | 743 | 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^] | 744 | ``N`` (POSIX only). |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 745 | |
| 746 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 747 | Windows Popen Helpers |
| 748 | --------------------- |
| 749 | |
| 750 | The :class:`STARTUPINFO` class and following constants are only available |
| 751 | on Windows. |
| 752 | |
| 753 | .. class:: STARTUPINFO() |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 754 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 755 | Partial support of the Windows |
| 756 | `STARTUPINFO <http://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx>`__ |
| 757 | structure is used for :class:`Popen` creation. |
| 758 | |
| 759 | .. attribute:: dwFlags |
| 760 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 761 | A bit field that determines whether certain :class:`STARTUPINFO` |
| 762 | attributes are used when the process creates a window. :: |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 763 | |
| 764 | si = subprocess.STARTUPINFO() |
| 765 | si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW |
| 766 | |
| 767 | .. attribute:: hStdInput |
| 768 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 769 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 770 | is the standard input handle for the process. If |
| 771 | :data:`STARTF_USESTDHANDLES` is not specified, the default for standard |
| 772 | input is the keyboard buffer. |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 773 | |
| 774 | .. attribute:: hStdOutput |
| 775 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 776 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 777 | is the standard output handle for the process. Otherwise, this attribute |
| 778 | 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] | 779 | buffer. |
| 780 | |
| 781 | .. attribute:: hStdError |
| 782 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 783 | If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this attribute |
| 784 | is the standard error handle for the process. Otherwise, this attribute is |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 785 | ignored and the default for standard error is the console window's buffer. |
| 786 | |
| 787 | .. attribute:: wShowWindow |
| 788 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 789 | If :attr:`dwFlags` specifies :data:`STARTF_USESHOWWINDOW`, this attribute |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 790 | can be any of the values that can be specified in the ``nCmdShow`` |
| 791 | parameter for the |
| 792 | `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] | 793 | function, except for ``SW_SHOWDEFAULT``. Otherwise, this attribute is |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 794 | ignored. |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 795 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 796 | :data:`SW_HIDE` is provided for this attribute. It is used when |
| 797 | :class:`Popen` is called with ``shell=True``. |
| 798 | |
| 799 | |
| 800 | Constants |
| 801 | ^^^^^^^^^ |
| 802 | |
| 803 | The :mod:`subprocess` module exposes the following constants. |
| 804 | |
| 805 | .. data:: STD_INPUT_HANDLE |
| 806 | |
| 807 | The standard input device. Initially, this is the console input buffer, |
| 808 | ``CONIN$``. |
| 809 | |
| 810 | .. data:: STD_OUTPUT_HANDLE |
| 811 | |
| 812 | The standard output device. Initially, this is the active console screen |
| 813 | buffer, ``CONOUT$``. |
| 814 | |
| 815 | .. data:: STD_ERROR_HANDLE |
| 816 | |
| 817 | The standard error device. Initially, this is the active console screen |
| 818 | buffer, ``CONOUT$``. |
| 819 | |
| 820 | .. data:: SW_HIDE |
| 821 | |
| 822 | Hides the window. Another window will be activated. |
| 823 | |
| 824 | .. data:: STARTF_USESTDHANDLES |
| 825 | |
| 826 | Specifies that the :attr:`STARTUPINFO.hStdInput`, |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 827 | :attr:`STARTUPINFO.hStdOutput`, and :attr:`STARTUPINFO.hStdError` attributes |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 828 | contain additional information. |
| 829 | |
| 830 | .. data:: STARTF_USESHOWWINDOW |
| 831 | |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 832 | Specifies that the :attr:`STARTUPINFO.wShowWindow` attribute contains |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 833 | additional information. |
| 834 | |
| 835 | .. data:: CREATE_NEW_CONSOLE |
| 836 | |
| 837 | The new process has a new console, instead of inheriting its parent's |
| 838 | console (the default). |
Brian Curtin | 73365dd | 2011-04-29 22:18:33 -0500 | [diff] [blame] | 839 | |
Brian Curtin | 3040193 | 2011-04-29 22:20:57 -0500 | [diff] [blame] | 840 | .. data:: CREATE_NEW_PROCESS_GROUP |
| 841 | |
| 842 | A :class:`Popen` ``creationflags`` parameter to specify that a new process |
| 843 | group will be created. This flag is necessary for using :func:`os.kill` |
| 844 | on the subprocess. |
| 845 | |
| 846 | This flag is ignored if :data:`CREATE_NEW_CONSOLE` is specified. |
| 847 | |
Brian Curtin | e6242d7 | 2011-04-29 22:17:51 -0500 | [diff] [blame] | 848 | |
Benjamin Peterson | dcf97b9 | 2008-07-02 17:30:14 +0000 | [diff] [blame] | 849 | .. _subprocess-replacements: |
| 850 | |
Ezio Melotti | 402f75d | 2012-11-08 10:07:10 +0200 | [diff] [blame] | 851 | Replacing Older Functions with the :mod:`subprocess` Module |
| 852 | ----------------------------------------------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 853 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 854 | 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] | 855 | |
| 856 | .. note:: |
| 857 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 858 | All "a" functions in this section fail (more or less) silently if the |
| 859 | executed program cannot be found; the "b" replacements raise :exc:`OSError` |
| 860 | instead. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 861 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 862 | In addition, the replacements using :func:`check_output` will fail with a |
| 863 | :exc:`CalledProcessError` if the requested operation produces a non-zero |
Serhiy Storchaka | 9e0ae53 | 2013-08-24 00:23:38 +0300 | [diff] [blame] | 864 | return code. The output is still available as the |
| 865 | :attr:`~CalledProcessError.output` attribute of the raised exception. |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 866 | |
| 867 | In the following examples, we assume that the relevant functions have already |
Ezio Melotti | 402f75d | 2012-11-08 10:07:10 +0200 | [diff] [blame] | 868 | been imported from the :mod:`subprocess` module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 869 | |
| 870 | |
| 871 | Replacing /bin/sh shell backquote |
| 872 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 873 | |
| 874 | :: |
| 875 | |
| 876 | output=`mycmd myarg` |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 877 | # becomes |
| 878 | output = check_output(["mycmd", "myarg"]) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 879 | |
| 880 | |
Benjamin Peterson | f10a79a | 2008-10-11 00:49:57 +0000 | [diff] [blame] | 881 | Replacing shell pipeline |
| 882 | ^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 883 | |
| 884 | :: |
| 885 | |
| 886 | output=`dmesg | grep hda` |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 887 | # becomes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 888 | p1 = Popen(["dmesg"], stdout=PIPE) |
| 889 | p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE) |
Gregory P. Smith | e09d2f1 | 2011-02-05 21:47:25 +0000 | [diff] [blame] | 890 | p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 891 | output = p2.communicate()[0] |
| 892 | |
Gregory P. Smith | e09d2f1 | 2011-02-05 21:47:25 +0000 | [diff] [blame] | 893 | The p1.stdout.close() call after starting the p2 is important in order for p1 |
| 894 | to receive a SIGPIPE if p2 exits before p1. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 895 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 896 | 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] | 897 | be used directly:: |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 898 | |
| 899 | output=`dmesg | grep hda` |
| 900 | # becomes |
| 901 | output=check_output("dmesg | grep hda", shell=True) |
| 902 | |
| 903 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 904 | Replacing :func:`os.system` |
| 905 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 906 | |
| 907 | :: |
| 908 | |
| 909 | sts = os.system("mycmd" + " myarg") |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 910 | # becomes |
| 911 | sts = call("mycmd" + " myarg", shell=True) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 912 | |
| 913 | Notes: |
| 914 | |
| 915 | * Calling the program through the shell is usually not required. |
| 916 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 917 | A more realistic example would look like this:: |
| 918 | |
| 919 | try: |
| 920 | retcode = call("mycmd" + " myarg", shell=True) |
| 921 | if retcode < 0: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 922 | print("Child was terminated by signal", -retcode, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 923 | else: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 924 | print("Child returned", retcode, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 925 | except OSError as e: |
Collin Winter | c79461b | 2007-09-01 23:34:30 +0000 | [diff] [blame] | 926 | print("Execution failed:", e, file=sys.stderr) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 927 | |
| 928 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 929 | Replacing the :func:`os.spawn <os.spawnl>` family |
| 930 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 931 | |
| 932 | P_NOWAIT example:: |
| 933 | |
| 934 | pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg") |
| 935 | ==> |
| 936 | pid = Popen(["/bin/mycmd", "myarg"]).pid |
| 937 | |
| 938 | P_WAIT example:: |
| 939 | |
| 940 | retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg") |
| 941 | ==> |
| 942 | retcode = call(["/bin/mycmd", "myarg"]) |
| 943 | |
| 944 | Vector example:: |
| 945 | |
| 946 | os.spawnvp(os.P_NOWAIT, path, args) |
| 947 | ==> |
| 948 | Popen([path] + args[1:]) |
| 949 | |
| 950 | Environment example:: |
| 951 | |
| 952 | os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env) |
| 953 | ==> |
| 954 | Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"}) |
| 955 | |
| 956 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 957 | |
| 958 | Replacing :func:`os.popen`, :func:`os.popen2`, :func:`os.popen3` |
| 959 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 960 | |
| 961 | :: |
| 962 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 963 | (child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 964 | ==> |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 965 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 966 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 967 | (child_stdin, child_stdout) = (p.stdin, p.stdout) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 968 | |
| 969 | :: |
| 970 | |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 971 | (child_stdin, |
| 972 | child_stdout, |
| 973 | child_stderr) = os.popen3(cmd, mode, bufsize) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 974 | ==> |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 975 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 976 | stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True) |
| 977 | (child_stdin, |
| 978 | child_stdout, |
| 979 | child_stderr) = (p.stdin, p.stdout, p.stderr) |
| 980 | |
| 981 | :: |
| 982 | |
| 983 | (child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize) |
| 984 | ==> |
| 985 | p = Popen(cmd, shell=True, bufsize=bufsize, |
| 986 | stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True) |
| 987 | (child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout) |
| 988 | |
| 989 | Return code handling translates as follows:: |
| 990 | |
| 991 | pipe = os.popen(cmd, 'w') |
| 992 | ... |
| 993 | rc = pipe.close() |
Stefan Krah | fc9e08d | 2010-07-14 10:16:11 +0000 | [diff] [blame] | 994 | if rc is not None and rc >> 8: |
Ezio Melotti | 985e24d | 2009-09-13 07:54:02 +0000 | [diff] [blame] | 995 | print("There were some errors") |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 996 | ==> |
| 997 | process = Popen(cmd, 'w', stdin=PIPE) |
| 998 | ... |
| 999 | process.stdin.close() |
| 1000 | if process.wait() != 0: |
Ezio Melotti | 985e24d | 2009-09-13 07:54:02 +0000 | [diff] [blame] | 1001 | print("There were some errors") |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1002 | |
| 1003 | |
| 1004 | Replacing functions from the :mod:`popen2` module |
| 1005 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 1006 | |
| 1007 | .. note:: |
| 1008 | |
| 1009 | If the cmd argument to popen2 functions is a string, the command is executed |
| 1010 | through /bin/sh. If it is a list, the command is directly executed. |
| 1011 | |
| 1012 | :: |
| 1013 | |
| 1014 | (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode) |
| 1015 | ==> |
| 1016 | p = Popen(["somestring"], shell=True, bufsize=bufsize, |
| 1017 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 1018 | (child_stdout, child_stdin) = (p.stdout, p.stdin) |
| 1019 | |
| 1020 | :: |
| 1021 | |
| 1022 | (child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode) |
| 1023 | ==> |
| 1024 | p = Popen(["mycmd", "myarg"], bufsize=bufsize, |
| 1025 | stdin=PIPE, stdout=PIPE, close_fds=True) |
| 1026 | (child_stdout, child_stdin) = (p.stdout, p.stdin) |
| 1027 | |
| 1028 | :class:`popen2.Popen3` and :class:`popen2.Popen4` basically work as |
| 1029 | :class:`subprocess.Popen`, except that: |
| 1030 | |
| 1031 | * :class:`Popen` raises an exception if the execution fails. |
| 1032 | |
| 1033 | * the *capturestderr* argument is replaced with the *stderr* argument. |
| 1034 | |
| 1035 | * ``stdin=PIPE`` and ``stdout=PIPE`` must be specified. |
| 1036 | |
| 1037 | * 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] | 1038 | ``close_fds=True`` with :class:`Popen` to guarantee this behavior on |
| 1039 | all platforms or past Python versions. |
Eli Bendersky | 046a764 | 2011-04-15 07:23:26 +0300 | [diff] [blame] | 1040 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1041 | |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1042 | Legacy Shell Invocation Functions |
Nick Coghlan | 32e4a58 | 2011-11-08 21:50:58 +1000 | [diff] [blame] | 1043 | --------------------------------- |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1044 | |
| 1045 | This module also provides the following legacy functions from the 2.x |
| 1046 | ``commands`` module. These operations implicitly invoke the system shell and |
| 1047 | none of the guarantees described above regarding security and exception |
| 1048 | handling consistency are valid for these functions. |
| 1049 | |
| 1050 | .. function:: getstatusoutput(cmd) |
| 1051 | |
| 1052 | Return ``(status, output)`` of executing *cmd* in a shell. |
| 1053 | |
Tim Golden | 6079814 | 2013-11-05 12:57:25 +0000 | [diff] [blame] | 1054 | Execute the string *cmd* in a shell with :meth:`Popen.check_output` and |
| 1055 | return a 2-tuple ``(status, output)``. Universal newlines mode is used; |
| 1056 | see the notes on :ref:`frequently-used-arguments` for more details. |
Tim Golden | 3a2abb5 | 2013-11-03 18:24:50 +0000 | [diff] [blame] | 1057 | |
| 1058 | A trailing newline is stripped from the output. |
| 1059 | The exit status for the command can be interpreted |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1060 | according to the rules for the C function :c:func:`wait`. Example:: |
| 1061 | |
| 1062 | >>> subprocess.getstatusoutput('ls /bin/ls') |
| 1063 | (0, '/bin/ls') |
| 1064 | >>> subprocess.getstatusoutput('cat /bin/junk') |
| 1065 | (256, 'cat: /bin/junk: No such file or directory') |
| 1066 | >>> subprocess.getstatusoutput('/bin/junk') |
| 1067 | (256, 'sh: /bin/junk: not found') |
| 1068 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 1069 | Availability: POSIX & Windows |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 1070 | |
| 1071 | .. versionchanged:: 3.3.4 |
| 1072 | Windows support added |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1073 | |
| 1074 | |
| 1075 | .. function:: getoutput(cmd) |
| 1076 | |
| 1077 | Return output (stdout and stderr) of executing *cmd* in a shell. |
| 1078 | |
| 1079 | Like :func:`getstatusoutput`, except the exit status is ignored and the return |
| 1080 | value is a string containing the command's output. Example:: |
| 1081 | |
| 1082 | >>> subprocess.getoutput('ls /bin/ls') |
| 1083 | '/bin/ls' |
| 1084 | |
Gregory P. Smith | 8e0aa05 | 2014-05-11 13:28:35 -0700 | [diff] [blame^] | 1085 | Availability: POSIX & Windows |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 1086 | |
| 1087 | .. versionchanged:: 3.3.4 |
| 1088 | Windows support added |
Nick Coghlan | c29248f | 2011-11-08 20:49:23 +1000 | [diff] [blame] | 1089 | |
Nick Coghlan | 32e4a58 | 2011-11-08 21:50:58 +1000 | [diff] [blame] | 1090 | |
Eli Bendersky | 046a764 | 2011-04-15 07:23:26 +0300 | [diff] [blame] | 1091 | Notes |
| 1092 | ----- |
| 1093 | |
| 1094 | .. _converting-argument-sequence: |
| 1095 | |
| 1096 | Converting an argument sequence to a string on Windows |
| 1097 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 1098 | |
| 1099 | On Windows, an *args* sequence is converted to a string that can be parsed |
| 1100 | using the following rules (which correspond to the rules used by the MS C |
| 1101 | runtime): |
| 1102 | |
| 1103 | 1. Arguments are delimited by white space, which is either a |
| 1104 | space or a tab. |
| 1105 | |
| 1106 | 2. A string surrounded by double quotation marks is |
| 1107 | interpreted as a single argument, regardless of white space |
| 1108 | contained within. A quoted string can be embedded in an |
| 1109 | argument. |
| 1110 | |
| 1111 | 3. A double quotation mark preceded by a backslash is |
| 1112 | interpreted as a literal double quotation mark. |
| 1113 | |
| 1114 | 4. Backslashes are interpreted literally, unless they |
| 1115 | immediately precede a double quotation mark. |
| 1116 | |
| 1117 | 5. If backslashes immediately precede a double quotation mark, |
| 1118 | every pair of backslashes is interpreted as a literal |
| 1119 | backslash. If the number of backslashes is odd, the last |
| 1120 | backslash escapes the next double quotation mark as |
| 1121 | described in rule 3. |
| 1122 | |
Eli Bendersky | d211231 | 2011-04-15 07:26:28 +0300 | [diff] [blame] | 1123 | |
Éric Araujo | 9bce311 | 2011-07-27 18:29:31 +0200 | [diff] [blame] | 1124 | .. seealso:: |
| 1125 | |
| 1126 | :mod:`shlex` |
| 1127 | Module which provides function to parse and escape command lines. |