fix documentation and test of getoutput

it returns both stdout and stderr
closes gh-3280

IPython/utils/_process_common.py

@@ -1,195 +1,196
 """Common utilities for the various process_* implementations.
 
 This file is only meant to be imported by the platform-specific implementations
 of subprocess utilities, and it contains tools that are common to all of them.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 import subprocess
 import shlex
 import sys
 
 from IPython.utils import py3compat
 
 #-----------------------------------------------------------------------------
 # Function definitions
 #-----------------------------------------------------------------------------
 
 def read_no_interrupt(p):
     """Read from a pipe ignoring EINTR errors.
 
     This is necessary because when reading from pipes with GUI event loops
     running in the background, often interrupts are raised that stop the
     command from completing."""
     import errno
 
     try:
         return p.read()
     except IOError as err:
         if err.errno != errno.EINTR:
             raise
 
 
 def process_handler(cmd, callback, stderr=subprocess.PIPE):
     """Open a command in a shell subprocess and execute a callback.
 
     This function provides common scaffolding for creating subprocess.Popen()
     calls.  It creates a Popen object and then calls the callback with it.
 
     Parameters
     ----------
     cmd : str
       A string to be executed with the underlying system shell (by calling
     :func:`Popen` with ``shell=True``.
 
     callback : callable
       A one-argument function that will be called with the Popen object.
 
     stderr : file descriptor number, optional
       By default this is set to ``subprocess.PIPE``, but you can also pass the
       value ``subprocess.STDOUT`` to force the subprocess' stderr to go into
       the same file descriptor as its stdout.  This is useful to read stdout
       and stderr combined in the order they are generated.
 
     Returns
     -------
     The return value of the provided callback is returned.
     """
     sys.stdout.flush()
     sys.stderr.flush()
     # On win32, close_fds can't be true when using pipes for stdin/out/err
     close_fds = sys.platform != 'win32'
     p = subprocess.Popen(cmd, shell=True,
                          stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE,
                          stderr=stderr,
                          close_fds=close_fds)
 
     try:
         out = callback(p)
     except KeyboardInterrupt:
         print('^C')
         sys.stdout.flush()
         sys.stderr.flush()
         out = None
     finally:
         # Make really sure that we don't leave processes behind, in case the
         # call above raises an exception
         # We start by assuming the subprocess finished (to avoid NameErrors
         # later depending on the path taken)
         if p.returncode is None:
             try:
                 p.terminate()
                 p.poll()
             except OSError:
                 pass
         # One last try on our way out
         if p.returncode is None:
             try:
                 p.kill()
             except OSError:
                 pass
 
     return out
 
 
 def getoutput(cmd):
-    """Return standard output of executing cmd in a shell.
-
-    Accepts the same arguments as os.system().
+    """Run a command and return its stdout/stderr as a string.
 
     Parameters
     ----------
     cmd : str
       A command to be executed in the system shell.
 
     Returns
     -------
-    stdout : str
+    output : str
+      A string containing the combination of stdout and stderr from the
+    subprocess, in whatever order the subprocess originally wrote to its
+    file descriptors (so the order of the information in this string is the
+    correct order as would be seen if running the command in a terminal).
     """
-
     out = process_handler(cmd, lambda p: p.communicate()[0], subprocess.STDOUT)
     if out is None:
         return ''
     return py3compat.bytes_to_str(out)
 
 
 def getoutputerror(cmd):
     """Return (standard output, standard error) of executing cmd in a shell.
 
     Accepts the same arguments as os.system().
 
     Parameters
     ----------
     cmd : str
       A command to be executed in the system shell.
 
     Returns
     -------
     stdout : str
     stderr : str
     """
 
     out_err = process_handler(cmd, lambda p: p.communicate())
     if out_err is None:
         return '', ''
     out, err = out_err
     return py3compat.bytes_to_str(out), py3compat.bytes_to_str(err)
 
 
 def arg_split(s, posix=False, strict=True):
     """Split a command line's arguments in a shell-like manner.
 
     This is a modified version of the standard library's shlex.split()
     function, but with a default of posix=False for splitting, so that quotes
     in inputs are respected.
 
     if strict=False, then any errors shlex.split would raise will result in the
     unparsed remainder being the last element of the list, rather than raising.
     This is because we sometimes use arg_split to parse things other than
     command-line args.
     """
 
     # Unfortunately, python's shlex module is buggy with unicode input:
     # http://bugs.python.org/issue1170
     # At least encoding the input when it's unicode seems to help, but there
     # may be more problems lurking.  Apparently this is fixed in python3.
     is_unicode = False
     if (not py3compat.PY3) and isinstance(s, unicode):
         is_unicode = True
         s = s.encode('utf-8')
     lex = shlex.shlex(s, posix=posix)
     lex.whitespace_split = True
     # Extract tokens, ensuring that things like leaving open quotes
     # does not cause this to raise.  This is important, because we
     # sometimes pass Python source through this (e.g. %timeit f(" ")),
     # and it shouldn't raise an exception.
     # It may be a bad idea to parse things that are not command-line args
     # through this function, but we do, so let's be safe about it.
     lex.commenters='' #fix for GH-1269
     tokens = []
     while True:
         try:
             tokens.append(next(lex))
         except StopIteration:
             break
         except ValueError:
             if strict:
                 raise
             # couldn't parse, get remaining blob as last token
             tokens.append(lex.token)
             break
     
     if is_unicode:
         # Convert the tokens back to unicode.
         tokens = [x.decode('utf-8') for x in tokens]
     return tokens

IPython/utils/tests/test_process.py

@@ -1,131 +1,135
 # encoding: utf-8
 """
 Tests for platutils.py
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import sys
 from unittest import TestCase
 
 import nose.tools as nt
 
 from IPython.utils.process import (find_cmd, FindCmdError, arg_split,
                                    system, getoutput, getoutputerror)
 from IPython.testing import decorators as dec
 from IPython.testing import tools as tt
 
 #-----------------------------------------------------------------------------
 # Tests
 #-----------------------------------------------------------------------------
 
 def test_find_cmd_python():
     """Make sure we find sys.exectable for python."""
     nt.assert_equal(find_cmd('python'), sys.executable)
 
     
 @dec.skip_win32
 def test_find_cmd_ls():
     """Make sure we can find the full path to ls."""
     path = find_cmd('ls')
     nt.assert_true(path.endswith('ls'))
 
     
 def has_pywin32():
     try:
         import win32api
     except ImportError:
         return False
     return True
 
 
 @dec.onlyif(has_pywin32, "This test requires win32api to run")
 def test_find_cmd_pythonw():
     """Try to find pythonw on Windows."""
     path = find_cmd('pythonw')
     nt.assert_true(path.endswith('pythonw.exe'))
 
 
 @dec.onlyif(lambda : sys.platform != 'win32' or has_pywin32(),
             "This test runs on posix or in win32 with win32api installed")
 def test_find_cmd_fail():
     """Make sure that FindCmdError is raised if we can't find the cmd."""
     nt.assert_raises(FindCmdError,find_cmd,'asdfasdf')
 
     
 @dec.skip_win32
 def test_arg_split():
     """Ensure that argument lines are correctly split like in a shell."""
     tests = [['hi', ['hi']],
              [u'hi', [u'hi']],
              ['hello there', ['hello', 'there']],
              # \u01ce == \N{LATIN SMALL LETTER A WITH CARON}
              # Do not use \N because the tests crash with syntax error in
              # some cases, for example windows python2.6.
              [u'h\u01cello', [u'h\u01cello']],
              ['something "with quotes"', ['something', '"with quotes"']],
              ]
     for argstr, argv in tests:
         nt.assert_equal(arg_split(argstr), argv)
     
 @dec.skip_if_not_win32
 def test_arg_split_win32():
     """Ensure that argument lines are correctly split like in a shell."""
     tests = [['hi', ['hi']],
              [u'hi', [u'hi']],
              ['hello there', ['hello', 'there']],
              [u'h\u01cello', [u'h\u01cello']],
              ['something "with quotes"', ['something', 'with quotes']],
              ]
     for argstr, argv in tests:
         nt.assert_equal(arg_split(argstr), argv)
 
 
 class SubProcessTestCase(TestCase, tt.TempFileMixin):
     def setUp(self):
         """Make a valid python temp file."""
         lines = ["from __future__ import print_function",
                  "import sys",
                  "print('on stdout', end='', file=sys.stdout)",
                  "print('on stderr', end='', file=sys.stderr)",
                  "sys.stdout.flush()",
                  "sys.stderr.flush()"]
         self.mktmp('\n'.join(lines))
 
     def test_system(self):
         status = system('python "%s"' % self.fname)
         self.assertEqual(status, 0)
 
     def test_system_quotes(self):
         status = system('python -c "import sys"')
         self.assertEqual(status, 0)
 
     def test_getoutput(self):
         out = getoutput('python "%s"' % self.fname)
-        self.assertEqual(out, 'on stdout')
+        # we can't rely on the order the line buffered streams are flushed
+        try:
+            self.assertEqual(out, 'on stderron stdout')
+        except AssertionError:
+            self.assertEqual(out, 'on stdouton stderr')
 
     def test_getoutput_quoted(self):
         out = getoutput('python -c "print (1)"')
         self.assertEqual(out.strip(), '1')
 
     #Invalid quoting on windows
     @dec.skip_win32
     def test_getoutput_quoted2(self):
         out = getoutput("python -c 'print (1)'")
         self.assertEqual(out.strip(), '1')
         out = getoutput("python -c 'print (\"1\")'")
         self.assertEqual(out.strip(), '1')
 
-    def test_getoutput(self):
+    def test_getoutput_error(self):
         out, err = getoutputerror('python "%s"' % self.fname)
         self.assertEqual(out, 'on stdout')
         self.assertEqual(err, 'on stderr')