# gevent

# `gevent.subprocess` – Cooperative `subprocess` module

Caution

On POSIX platforms, this module is not usable from native threads other than the main thread; attempting to do so will raise a `TypeError`. This module depends on libev’s fork watchers. On POSIX systems, fork watchers are implemented using signals, and the thread to which process-directed signals are delivered is not defined. Because each native thread has its own gevent/libev loop, this means that a fork watcher registered with one loop (thread) may never see the signal about a child it spawned if the signal is sent to a different thread.

Note

The interface of this module is intended to match that of the standard library `subprocess` module (with many backwards compatible extensions from Python 3 backported to Python 2). There are some small differences between the Python 2 and Python 3 versions of that module (the Python 2 `TimeoutExpired` exception, notably, extends `Timeout` and there is no `SubprocessError`) and between the POSIX and Windows versions. The HTML documentation here can only describe one version; for definitive documentation, see the standard library or the source code.

exception `CalledProcessError`(returncode, cmd, output=None, stderr=None)

  Bases: `subprocess.SubprocessError`

  Raised when run() is called with check=True and the process returns a non-zero exit status.

  Attributes:
    cmd, returncode, stdout, stderr, output
  `stdout`

    Alias for output attribute, to match stderr

exception `SubprocessError`

  Bases: `Exception`

exception `TimeoutExpired`(cmd, timeout, output=None, stderr=None)

  Bases: `subprocess.SubprocessError`

  This exception is raised when the timeout expires while waiting for a child process.

  Attributes:
    cmd, output, stdout, stderr, timeout

class `Popen`(args, bufsize=-1, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=<object object>, shell=False, cwd=None, env=None, universal_newlines=None, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False, pass_fds=(), encoding=None, errors=None, text=None, threadpool=None)

  Bases: `object`

  The underlying process creation and management in this module is handled by the Popen class. It offers a lot of flexibility so that developers are able to handle the less common cases not covered by the convenience functions.

  See also

  `subprocess.Popen` This class should have the same interface as the standard library class.

  Changed in version 1.2a1: Instances can now be used as context managers under Python 2.7. Previously this was restricted to Python 3.

  Changed in version 1.2a1: Instances now save the `args` attribute under Python 2.7. Previously this was restricted to Python 3.

  Changed in version 1.2b1: Add the `encoding` and `errors` parameters for Python 3.

  Changed in version 1.3a1: Accept “path-like” objects for the cwd parameter on all platforms. This was added to Python 3.6. Previously with gevent, it only worked on POSIX platforms on 3.6.

  Changed in version 1.3a1: Add the `text` argument as a synonym for `universal_newlines`, as added on Python 3.7.

  Changed in version 1.3a2: Allow the same keyword arguments under Python 2 as Python 3: `pass_fds`, `start_new_session`, `restore_signals`, `encoding` and `errors`. Under Python 2, `encoding` and `errors` are ignored because native handling of universal newlines is used.

  Changed in version 1.3a2: Under Python 2, `restore_signals` defaults to `False`. Previously it defaulted to `True`, the same as it did in Python 3.

  `communicate`(input=None, timeout=None)

    Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child.

    communicate() returns a tuple (stdout, stderr).

    Parameters: | timeout – Under Python 2, this is a gevent extension; if given and it expires, we will raise `TimeoutExpired`, which extends `gevent.timeout.Timeout` (note that this only extends `BaseException`, not `Exception`) Under Python 3, this raises the standard `TimeoutExpired` exception.

    Changed in version 1.1a2: Under Python 2, if the timeout elapses, raise the `gevent.timeout.Timeout` exception. Previously, we silently returned.

    Changed in version 1.1b5: Honor a timeout even if there’s no way to communicate with the child (stdin, stdout, and stderr are not pipes).

  `kill`()

    Kill the process with SIGKILL

  `pipe_cloexec`()

    Create a pipe with FDs set CLOEXEC.

  `poll`()

    Check if child process has terminated. Set and return `returncode` attribute.

  `send_signal`(sig)

    Send a signal to the process

  `terminate`()

    Terminate the process with SIGTERM

  `wait`(timeout=None, _raise_exc=True)

    Wait for child process to terminate. Returns `returncode` attribute.

    Parameters: | timeout – The floating point number of seconds to wait. Under Python 2, this is a gevent extension, and we simply return if it expires. Under Python 3, if this time elapses without finishing the process, `TimeoutExpired` is raised.

class `CompletedProcess`(args, returncode, stdout=None, stderr=None)

  Bases: `object`

  A process that has finished running.

  This is returned by run().

  Attributes:
    - args: The list or str args passed to run().
    - returncode: The exit code of the process, negative for signals.
    - stdout: The standard output (None if not captured).
    - stderr: The standard error (None if not captured).

  New in version 1.2a1: This first appeared in Python 3.5 and is available to all Python versions in gevent.

  `check_returncode`()

    Raise CalledProcessError if the exit code is non-zero.

`call`(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) → returncode

  Run command with arguments. Wait for command to complete or timeout, then return the returncode attribute.

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

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

  Changed in version 1.2a1: The `timeout` keyword argument is now accepted on all supported versions of Python (not just Python 3) and if it expires will raise a `TimeoutExpired` exception (under Python 2 this is a subclass of `Timeout`).

`check_call`(args, *, stdin=None, stdout=None, stderr=None, shell=False, timeout=None) → 0

  Run command with arguments. Wait for command to complete. If the exit code was zero then return, otherwise raise `CalledProcessError`. The `CalledProcessError` object will have the return code in the returncode attribute.

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

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

`check_output`(args, *, input=None, stdin=None, stderr=None, shell=False, universal_newlines=False, timeout=None) → output

  Run command with arguments and return its output.

  If the exit code was non-zero it raises a `CalledProcessError`. The `CalledProcessError` object will have the return code in the returncode attribute and output in the output attribute.

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

      >>> check_output(["ls", "-1", "/dev/null"])
      '/dev/null\n'

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

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

      >>> print(check_output(["/bin/sh", "-c",
      ...               "ls -l non_existent_file ; exit 0"],
      ...              stderr=STDOUT).decode('ascii').strip())
      ls: non_existent_file: No such file or directory

  There is an additional optional argument, “input”, allowing you to pass a string to the subprocess’s stdin. If you use this argument you may not also use the Popen constructor’s “stdin” argument, as it too will be used internally. Example:

      >>> check_output(["sed", "-e", "s/foo/bar/"],
      ...              input=b"when in the course of fooman events\n")
      'when in the course of barman events\n'

  If `universal_newlines=True` is passed, the return value will be a string rather than bytes.

  Changed in version 1.2a1: The `timeout` keyword argument is now accepted on all supported versions of Python (not just Python 3) and if it expires will raise a `TimeoutExpired` exception (under Python 2 this is a subclass of `Timeout`).

  Changed in version 1.2a1: The `input` keyword argument is now accepted on all supported versions of Python, not just Python 3

`run`(args, *, stdin=None, input=None, stdout=None, stderr=None, shell=False, timeout=None, check=False) → CompletedProcess

  Run command with arguments and return a CompletedProcess instance.

  The returned instance will have attributes args, returncode, stdout and stderr. By default, stdout and stderr are not captured, and those attributes will be None. Pass stdout=PIPE and/or stderr=PIPE in order to capture them. If check is True and the exit code was non-zero, it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute, and output & stderr attributes if those streams were captured.

  If timeout is given, and the process takes too long, a TimeoutExpired exception will be raised.

  There is an optional argument “input”, allowing you to pass a string to the subprocess’s stdin. If you use this argument you may not also use the Popen constructor’s “stdin” argument, as it will be used internally. The other arguments are the same as for the Popen constructor. If universal_newlines=True is passed, the “input” argument must be a string and stdout/stderr in the returned object will be strings rather than bytes.

  New in version 1.2a1: This function first appeared in Python 3.5. It is available on all Python versions gevent supports.

  Changed in version 1.3a2: Add the `capture_output` argument from Python 3.7. It automatically sets `stdout` and `stderr` to `PIPE`. It is an error to pass either of those arguments along with `capture_output`.

`getstatusoutput`(cmd)

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

  Execute the string ‘cmd’ in a shell with ‘check_output’ and return a 2-tuple (status, output). The locale encoding is used to decode the output and process newlines.

  A trailing newline is stripped from the output. The exit status for the command can be interpreted according to the rules for the function ‘wait’. Example:

      >>> import subprocess
      >>> subprocess.getstatusoutput('ls /bin/ls')
      (0, '/bin/ls')
      >>> subprocess.getstatusoutput('cat /bin/junk')
      (1, 'cat: /bin/junk: No such file or directory')
      >>> subprocess.getstatusoutput('/bin/junk')
      (127, 'sh: /bin/junk: not found')
      >>> subprocess.getstatusoutput('/bin/kill $$')
      (-15, '')

`getoutput`(cmd)

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

  Like getstatusoutput(), except the exit status is ignored and the return value is a string containing the command’s output. Example:

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

Next page: `gevent.thread` – Implementation of the standard `thread` module that spawns greenlets