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"""Common utilities for the various process_* implementations.
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This file is only meant to be imported by the platform-specific implementations
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of subprocess utilities, and it contains tools that are common to all of them.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2010-2011 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import subprocess
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import shlex
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import sys
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import os
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from IPython.utils import py3compat
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#-----------------------------------------------------------------------------
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# Function definitions
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#-----------------------------------------------------------------------------
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def read_no_interrupt(p):
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"""Read from a pipe ignoring EINTR errors.
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This is necessary because when reading from pipes with GUI event loops
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running in the background, often interrupts are raised that stop the
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command from completing."""
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import errno
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try:
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return p.read()
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except IOError as err:
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if err.errno != errno.EINTR:
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raise
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def process_handler(cmd, callback, stderr=subprocess.PIPE):
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"""Open a command in a shell subprocess and execute a callback.
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This function provides common scaffolding for creating subprocess.Popen()
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calls. It creates a Popen object and then calls the callback with it.
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Parameters
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----------
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cmd : str or list
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A command to be executed by the system, using :class:`subprocess.Popen`.
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If a string is passed, it will be run in the system shell. If a list is
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passed, it will be used directly as arguments.
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callback : callable
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A one-argument function that will be called with the Popen object.
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stderr : file descriptor number, optional
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By default this is set to ``subprocess.PIPE``, but you can also pass the
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value ``subprocess.STDOUT`` to force the subprocess' stderr to go into
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the same file descriptor as its stdout. This is useful to read stdout
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and stderr combined in the order they are generated.
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Returns
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-------
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The return value of the provided callback is returned.
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"""
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sys.stdout.flush()
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sys.stderr.flush()
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# On win32, close_fds can't be true when using pipes for stdin/out/err
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close_fds = sys.platform != 'win32'
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# Determine if cmd should be run with system shell.
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shell = isinstance(cmd, str)
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# On POSIX systems run shell commands with user-preferred shell.
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executable = None
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if shell and os.name == 'posix' and 'SHELL' in os.environ:
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executable = os.environ['SHELL']
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p = subprocess.Popen(cmd, shell=shell,
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executable=executable,
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=stderr,
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close_fds=close_fds)
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try:
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out = callback(p)
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except KeyboardInterrupt:
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print('^C')
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sys.stdout.flush()
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sys.stderr.flush()
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out = None
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finally:
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# Make really sure that we don't leave processes behind, in case the
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# call above raises an exception
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# We start by assuming the subprocess finished (to avoid NameErrors
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# later depending on the path taken)
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if p.returncode is None:
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try:
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p.terminate()
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p.poll()
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except OSError:
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pass
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# One last try on our way out
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if p.returncode is None:
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try:
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p.kill()
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except OSError:
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pass
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return out
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def getoutput(cmd):
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"""Run a command and return its stdout/stderr as a string.
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Parameters
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----------
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cmd : str or list
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A command to be executed in the system shell.
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Returns
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-------
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output : str
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A string containing the combination of stdout and stderr from the
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subprocess, in whatever order the subprocess originally wrote to its
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file descriptors (so the order of the information in this string is the
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correct order as would be seen if running the command in a terminal).
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"""
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out = process_handler(cmd, lambda p: p.communicate()[0], subprocess.STDOUT)
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if out is None:
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return ''
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return py3compat.bytes_to_str(out)
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def getoutputerror(cmd):
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"""Return (standard output, standard error) of executing cmd in a shell.
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Accepts the same arguments as os.system().
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Parameters
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----------
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cmd : str or list
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A command to be executed in the system shell.
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Returns
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-------
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stdout : str
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stderr : str
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"""
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return get_output_error_code(cmd)[:2]
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def get_output_error_code(cmd):
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"""Return (standard output, standard error, return code) of executing cmd
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in a shell.
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Accepts the same arguments as os.system().
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Parameters
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----------
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cmd : str or list
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A command to be executed in the system shell.
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Returns
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-------
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stdout : str
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stderr : str
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returncode: int
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"""
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out_err, p = process_handler(cmd, lambda p: (p.communicate(), p))
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if out_err is None:
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return '', '', p.returncode
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out, err = out_err
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return py3compat.bytes_to_str(out), py3compat.bytes_to_str(err), p.returncode
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def arg_split(s, posix=False, strict=True):
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"""Split a command line's arguments in a shell-like manner.
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This is a modified version of the standard library's shlex.split()
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function, but with a default of posix=False for splitting, so that quotes
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in inputs are respected.
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if strict=False, then any errors shlex.split would raise will result in the
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unparsed remainder being the last element of the list, rather than raising.
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This is because we sometimes use arg_split to parse things other than
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command-line args.
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"""
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lex = shlex.shlex(s, posix=posix)
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lex.whitespace_split = True
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# Extract tokens, ensuring that things like leaving open quotes
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# does not cause this to raise. This is important, because we
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# sometimes pass Python source through this (e.g. %timeit f(" ")),
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# and it shouldn't raise an exception.
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# It may be a bad idea to parse things that are not command-line args
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# through this function, but we do, so let's be safe about it.
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lex.commenters='' #fix for GH-1269
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tokens = []
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while True:
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try:
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tokens.append(next(lex))
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except StopIteration:
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break
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except ValueError:
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if strict:
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raise
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# couldn't parse, get remaining blob as last token
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tokens.append(lex.token)
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break
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return tokens
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