test_subprocess.py

import unittest
from test import support
import subprocess
import sys
import signal
import os
import errno
import tempfile
import time
import re
import sysconfig
try:
    import gc
except ImportError:
    gc = None

mswindows = (sys.platform == "win32")

#
# Depends on the following external programs: Python
#

if mswindows:
    SETBINARY = ('import msvcrt; msvcrt.setmode(sys.stdout.fileno(), '
                                                'os.O_BINARY);')
else:
    SETBINARY = ''


try:
    mkstemp = tempfile.mkstemp
except AttributeError:
    # tempfile.mkstemp is not available
    def mkstemp():
        """Replacement for mkstemp, calling mktemp."""
        fname = tempfile.mktemp()
        return os.open(fname, os.O_RDWR|os.O_CREAT), fname


class BaseTestCase(unittest.TestCase):
    def setUp(self):
        # Try to minimize the number of children we have so this test
        # doesn't crash on some buildbots (Alphas in particular).
        support.reap_children()

    def tearDown(self):
        for inst in subprocess._active:
            inst.wait()
        subprocess._cleanup()
        self.assertFalse(subprocess._active, "subprocess._active not empty")

    def assertStderrEqual(self, stderr, expected, msg=None):
        # In a debug build, stuff like "[6580 refs]" is printed to stderr at
        # shutdown time.  That frustrates tests trying to check stderr produced
        # from a spawned Python process.
        actual = support.strip_python_stderr(stderr)
        self.assertEqual(actual, expected, msg)


class ProcessTestCase(BaseTestCase):

    def test_call_seq(self):
        # call() function with sequence argument
        rc = subprocess.call([sys.executable, "-c",
                              "import sys; sys.exit(47)"])
        self.assertEqual(rc, 47)

    def test_check_call_zero(self):
        # check_call() function with zero return code
        rc = subprocess.check_call([sys.executable, "-c",
                                    "import sys; sys.exit(0)"])
        self.assertEqual(rc, 0)

    def test_check_call_nonzero(self):
        # check_call() function with non-zero return code
        with self.assertRaises(subprocess.CalledProcessError) as c:
            subprocess.check_call([sys.executable, "-c",
                                   "import sys; sys.exit(47)"])
        self.assertEqual(c.exception.returncode, 47)

    def test_check_output(self):
        # check_output() function with zero return code
        output = subprocess.check_output(
                [sys.executable, "-c", "print('BDFL')"])
        self.assertIn(b'BDFL', output)

    def test_check_output_nonzero(self):
        # check_call() function with non-zero return code
        with self.assertRaises(subprocess.CalledProcessError) as c:
            subprocess.check_output(
                    [sys.executable, "-c", "import sys; sys.exit(5)"])
        self.assertEqual(c.exception.returncode, 5)

    def test_check_output_stderr(self):
        # check_output() function stderr redirected to stdout
        output = subprocess.check_output(
                [sys.executable, "-c", "import sys; sys.stderr.write('BDFL')"],
                stderr=subprocess.STDOUT)
        self.assertIn(b'BDFL', output)

    def test_check_output_stdout_arg(self):
        # check_output() function stderr redirected to stdout
        with self.assertRaises(ValueError) as c:
            output = subprocess.check_output(
                    [sys.executable, "-c", "print('will not be run')"],
                    stdout=sys.stdout)
            self.fail("Expected ValueError when stdout arg supplied.")
        self.assertIn('stdout', c.exception.args[0])

    def test_call_kwargs(self):
        # call() function with keyword args
        newenv = os.environ.copy()
        newenv["FRUIT"] = "banana"
        rc = subprocess.call([sys.executable, "-c",
                              'import sys, os;'
                              'sys.exit(os.getenv("FRUIT")=="banana")'],
                             env=newenv)
        self.assertEqual(rc, 1)

    def test_stdin_none(self):
        # .stdin is None when not redirected
        p = subprocess.Popen([sys.executable, "-c", 'print("banana")'],
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        p.wait()
        self.assertEqual(p.stdin, None)

    def test_stdout_none(self):
        # .stdout is None when not redirected
        p = subprocess.Popen([sys.executable, "-c",
                             'print("    this bit of output is from a '
                             'test of stdout in a different '
                             'process ...")'],
                             stdin=subprocess.PIPE, stderr=subprocess.PIPE)
        p.wait()
        self.assertEqual(p.stdout, None)

    def test_stderr_none(self):
        # .stderr is None when not redirected
        p = subprocess.Popen([sys.executable, "-c", 'print("banana")'],
                         stdin=subprocess.PIPE, stdout=subprocess.PIPE)
        p.wait()
        self.assertEqual(p.stderr, None)

    def test_executable_with_cwd(self):
        python_dir = os.path.dirname(os.path.realpath(sys.executable))
        p = subprocess.Popen(["somethingyoudonthave", "-c",
                              "import sys; sys.exit(47)"],
                             executable=sys.executable, cwd=python_dir)
        p.wait()
        self.assertEqual(p.returncode, 47)

    @unittest.skipIf(sysconfig.is_python_build(),
                     "need an installed Python. See #7774")
    def test_executable_without_cwd(self):
        # For a normal installation, it should work without 'cwd'
        # argument.  For test runs in the build directory, see #7774.
        p = subprocess.Popen(["somethingyoudonthave", "-c",
                              "import sys; sys.exit(47)"],
                             executable=sys.executable)
        p.wait()
        self.assertEqual(p.returncode, 47)

    def test_stdin_pipe(self):
        # stdin redirection
        p = subprocess.Popen([sys.executable, "-c",
                         'import sys; sys.exit(sys.stdin.read() == "pear")'],
                        stdin=subprocess.PIPE)
        p.stdin.write(b"pear")
        p.stdin.close()
        p.wait()
        self.assertEqual(p.returncode, 1)

    def test_stdin_filedes(self):
        # stdin is set to open file descriptor
        tf = tempfile.TemporaryFile()
        d = tf.fileno()
        os.write(d, b"pear")
        os.lseek(d, 0, 0)
        p = subprocess.Popen([sys.executable, "-c",
                         'import sys; sys.exit(sys.stdin.read() == "pear")'],
                         stdin=d)
        p.wait()
        self.assertEqual(p.returncode, 1)

    def test_stdin_fileobj(self):
        # stdin is set to open file object
        tf = tempfile.TemporaryFile()
        tf.write(b"pear")
        tf.seek(0)
        p = subprocess.Popen([sys.executable, "-c",
                         'import sys; sys.exit(sys.stdin.read() == "pear")'],
                         stdin=tf)
        p.wait()
        self.assertEqual(p.returncode, 1)

    def test_stdout_pipe(self):
        # stdout redirection
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stdout.write("orange")'],
                         stdout=subprocess.PIPE)
        self.assertEqual(p.stdout.read(), b"orange")

    def test_stdout_filedes(self):
        # stdout is set to open file descriptor
        tf = tempfile.TemporaryFile()
        d = tf.fileno()
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stdout.write("orange")'],
                         stdout=d)
        p.wait()
        os.lseek(d, 0, 0)
        self.assertEqual(os.read(d, 1024), b"orange")

    def test_stdout_fileobj(self):
        # stdout is set to open file object
        tf = tempfile.TemporaryFile()
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stdout.write("orange")'],
                         stdout=tf)
        p.wait()
        tf.seek(0)
        self.assertEqual(tf.read(), b"orange")

    def test_stderr_pipe(self):
        # stderr redirection
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stderr.write("strawberry")'],
                         stderr=subprocess.PIPE)
        self.assertStderrEqual(p.stderr.read(), b"strawberry")

    def test_stderr_filedes(self):
        # stderr is set to open file descriptor
        tf = tempfile.TemporaryFile()
        d = tf.fileno()
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stderr.write("strawberry")'],
                         stderr=d)
        p.wait()
        os.lseek(d, 0, 0)
        self.assertStderrEqual(os.read(d, 1024), b"strawberry")

    def test_stderr_fileobj(self):
        # stderr is set to open file object
        tf = tempfile.TemporaryFile()
        p = subprocess.Popen([sys.executable, "-c",
                          'import sys; sys.stderr.write("strawberry")'],
                         stderr=tf)
        p.wait()
        tf.seek(0)
        self.assertStderrEqual(tf.read(), b"strawberry")

    def test_stdout_stderr_pipe(self):
        # capture stdout and stderr to the same pipe
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys;'
                              'sys.stdout.write("apple");'
                              'sys.stdout.flush();'
                              'sys.stderr.write("orange")'],
                             stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
        self.assertStderrEqual(p.stdout.read(), b"appleorange")

    def test_stdout_stderr_file(self):
        # capture stdout and stderr to the same open file
        tf = tempfile.TemporaryFile()
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys;'
                              'sys.stdout.write("apple");'
                              'sys.stdout.flush();'
                              'sys.stderr.write("orange")'],
                             stdout=tf,
                             stderr=tf)
        p.wait()
        tf.seek(0)
        self.assertStderrEqual(tf.read(), b"appleorange")

    def test_stdout_filedes_of_stdout(self):
        # stdout is set to 1 (#1531862).
        cmd = r"import sys, os; sys.exit(os.write(sys.stdout.fileno(), b'.\n'))"
        rc = subprocess.call([sys.executable, "-c", cmd], stdout=1)
        self.assertEqual(rc, 2)

    def test_cwd(self):
        tmpdir = tempfile.gettempdir()
        # We cannot use os.path.realpath to canonicalize the path,
        # since it doesn't expand Tru64 {memb} strings. See bug 1063571.
        cwd = os.getcwd()
        os.chdir(tmpdir)
        tmpdir = os.getcwd()
        os.chdir(cwd)
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(os.getcwd())'],
                             stdout=subprocess.PIPE,
                             cwd=tmpdir)
        normcase = os.path.normcase
        self.assertEqual(normcase(p.stdout.read().decode("utf-8")),
                         normcase(tmpdir))

    def test_env(self):
        newenv = os.environ.copy()
        newenv["FRUIT"] = "orange"
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(os.getenv("FRUIT"))'],
                             stdout=subprocess.PIPE,
                             env=newenv)
        self.assertEqual(p.stdout.read(), b"orange")

    def test_communicate_stdin(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys;'
                              'sys.exit(sys.stdin.read() == "pear")'],
                             stdin=subprocess.PIPE)
        p.communicate(b"pear")
        self.assertEqual(p.returncode, 1)

    def test_communicate_stdout(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys; sys.stdout.write("pineapple")'],
                             stdout=subprocess.PIPE)
        (stdout, stderr) = p.communicate()
        self.assertEqual(stdout, b"pineapple")
        self.assertEqual(stderr, None)

    def test_communicate_stderr(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys; sys.stderr.write("pineapple")'],
                             stderr=subprocess.PIPE)
        (stdout, stderr) = p.communicate()
        self.assertEqual(stdout, None)
        self.assertStderrEqual(stderr, b"pineapple")

    def test_communicate(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stderr.write("pineapple");'
                              'sys.stdout.write(sys.stdin.read())'],
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        (stdout, stderr) = p.communicate(b"banana")
        self.assertEqual(stdout, b"banana")
        self.assertStderrEqual(stderr, b"pineapple")

    # This test is Linux specific for simplicity to at least have
    # some coverage.  It is not a platform specific bug.
    @unittest.skipUnless(os.path.isdir('/proc/%d/fd' % os.getpid()),
                         "Linux specific")
    # Test for the fd leak reported in http://bugs.python.org/issue2791.
    def test_communicate_pipe_fd_leak(self):
        fd_directory = '/proc/%d/fd' % os.getpid()
        num_fds_before_popen = len(os.listdir(fd_directory))
        p = subprocess.Popen([sys.executable, "-c", "print()"],
                             stdout=subprocess.PIPE)
        p.communicate()
        num_fds_after_communicate = len(os.listdir(fd_directory))
        del p
        num_fds_after_destruction = len(os.listdir(fd_directory))
        self.assertEqual(num_fds_before_popen, num_fds_after_destruction)
        self.assertEqual(num_fds_before_popen, num_fds_after_communicate)

    def test_communicate_returns(self):
        # communicate() should return None if no redirection is active
        p = subprocess.Popen([sys.executable, "-c",
                              "import sys; sys.exit(47)"])
        (stdout, stderr) = p.communicate()
        self.assertEqual(stdout, None)
        self.assertEqual(stderr, None)

    def test_communicate_pipe_buf(self):
        # communicate() with writes larger than pipe_buf
        # This test will probably deadlock rather than fail, if
        # communicate() does not work properly.
        x, y = os.pipe()
        if mswindows:
            pipe_buf = 512
        else:
            pipe_buf = os.fpathconf(x, "PC_PIPE_BUF")
        os.close(x)
        os.close(y)
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(sys.stdin.read(47));'
                              'sys.stderr.write("xyz"*%d);'
                              'sys.stdout.write(sys.stdin.read())' % pipe_buf],
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        string_to_write = b"abc"*pipe_buf
        (stdout, stderr) = p.communicate(string_to_write)
        self.assertEqual(stdout, string_to_write)

    def test_writes_before_communicate(self):
        # stdin.write before communicate()
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(sys.stdin.read())'],
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        p.stdin.write(b"banana")
        (stdout, stderr) = p.communicate(b"split")
        self.assertEqual(stdout, b"bananasplit")
        self.assertStderrEqual(stderr, b"")

    def test_universal_newlines(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;' + SETBINARY +
                              'sys.stdout.write("line1\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line2\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line3\\r\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line4\\r");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("\\nline5");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("\\nline6");'],
                             stdout=subprocess.PIPE,
                             universal_newlines=1)
        stdout = p.stdout.read()
        self.assertEqual(stdout, "line1\nline2\nline3\nline4\nline5\nline6")

    def test_universal_newlines_communicate(self):
        # universal newlines through communicate()
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;' + SETBINARY +
                              'sys.stdout.write("line1\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line2\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line3\\r\\n");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("line4\\r");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("\\nline5");'
                              'sys.stdout.flush();'
                              'sys.stdout.write("\\nline6");'],
                             stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                             universal_newlines=1)
        (stdout, stderr) = p.communicate()
        self.assertEqual(stdout, "line1\nline2\nline3\nline4\nline5\nline6")

    def test_no_leaking(self):
        # Make sure we leak no resources
        if not mswindows:
            max_handles = 1026 # too much for most UNIX systems
        else:
            max_handles = 2050 # too much for (at least some) Windows setups
        handles = []
        try:
            for i in range(max_handles):
                try:
                    handles.append(os.open(support.TESTFN,
                                           os.O_WRONLY | os.O_CREAT))
                except OSError as e:
                    if e.errno != errno.EMFILE:
                        raise
                    break
            else:
                self.skipTest("failed to reach the file descriptor limit "
                    "(tried %d)" % max_handles)
            # Close a couple of them (should be enough for a subprocess)
            for i in range(10):
                os.close(handles.pop())
            # Loop creating some subprocesses. If one of them leaks some fds,
            # the next loop iteration will fail by reaching the max fd limit.
            for i in range(15):
                p = subprocess.Popen([sys.executable, "-c",
                                      "import sys;"
                                      "sys.stdout.write(sys.stdin.read())"],
                                     stdin=subprocess.PIPE,
                                     stdout=subprocess.PIPE,
                                     stderr=subprocess.PIPE)
                data = p.communicate(b"lime")[0]
                self.assertEqual(data, b"lime")
        finally:
            for h in handles:
                os.close(h)

    def test_list2cmdline(self):
        self.assertEqual(subprocess.list2cmdline(['a b c', 'd', 'e']),
                         '"a b c" d e')
        self.assertEqual(subprocess.list2cmdline(['ab"c', '\\', 'd']),
                         'ab\\"c \\ d')
        self.assertEqual(subprocess.list2cmdline(['ab"c', ' \\', 'd']),
                         'ab\\"c " \\\\" d')
        self.assertEqual(subprocess.list2cmdline(['a\\\\\\b', 'de fg', 'h']),
                         'a\\\\\\b "de fg" h')
        self.assertEqual(subprocess.list2cmdline(['a\\"b', 'c', 'd']),
                         'a\\\\\\"b c d')
        self.assertEqual(subprocess.list2cmdline(['a\\\\b c', 'd', 'e']),
                         '"a\\\\b c" d e')
        self.assertEqual(subprocess.list2cmdline(['a\\\\b\\ c', 'd', 'e']),
                         '"a\\\\b\\ c" d e')
        self.assertEqual(subprocess.list2cmdline(['ab', '']),
                         'ab ""')


    def test_poll(self):
        p = subprocess.Popen([sys.executable,
                          "-c", "import time; time.sleep(1)"])
        count = 0
        while p.poll() is None:
            time.sleep(0.1)
            count += 1
        # We expect that the poll loop probably went around about 10 times,
        # but, based on system scheduling we can't control, it's possible
        # poll() never returned None.  It "should be" very rare that it
        # didn't go around at least twice.
        self.assertGreaterEqual(count, 2)
        # Subsequent invocations should just return the returncode
        self.assertEqual(p.poll(), 0)


    def test_wait(self):
        p = subprocess.Popen([sys.executable,
                          "-c", "import time; time.sleep(2)"])
        self.assertEqual(p.wait(), 0)
        # Subsequent invocations should just return the returncode
        self.assertEqual(p.wait(), 0)


    def test_invalid_bufsize(self):
        # an invalid type of the bufsize argument should raise
        # TypeError.
        with self.assertRaises(TypeError):
            subprocess.Popen([sys.executable, "-c", "pass"], "orange")

    def test_bufsize_is_none(self):
        # bufsize=None should be the same as bufsize=0.
        p = subprocess.Popen([sys.executable, "-c", "pass"], None)
        self.assertEqual(p.wait(), 0)
        # Again with keyword arg
        p = subprocess.Popen([sys.executable, "-c", "pass"], bufsize=None)
        self.assertEqual(p.wait(), 0)

    def test_leaking_fds_on_error(self):
        # see bug #5179: Popen leaks file descriptors to PIPEs if
        # the child fails to execute; this will eventually exhaust
        # the maximum number of open fds. 1024 seems a very common
        # value for that limit, but Windows has 2048, so we loop
        # 1024 times (each call leaked two fds).
        for i in range(1024):
            # Windows raises IOError.  Others raise OSError.
            with self.assertRaises(EnvironmentError) as c:
                subprocess.Popen(['nonexisting_i_hope'],
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE)
            if c.exception.errno != errno.ENOENT:  # ignore "no such file"
                raise c.exception

    def test_issue8780(self):
        # Ensure that stdout is inherited from the parent
        # if stdout=PIPE is not used
        code = ';'.join((
            'import subprocess, sys',
            'retcode = subprocess.call('
                "[sys.executable, '-c', 'print(\"Hello World!\")'])",
            'assert retcode == 0'))
        output = subprocess.check_output([sys.executable, '-c', code])
        self.assert_(output.startswith(b'Hello World!'), ascii(output))

    def test_handles_closed_on_exception(self):
        # If CreateProcess exits with an error, ensure the
        # duplicate output handles are released
        ifhandle, ifname = mkstemp()
        ofhandle, ofname = mkstemp()
        efhandle, efname = mkstemp()
        try:
            subprocess.Popen (["*"], stdin=ifhandle, stdout=ofhandle,
              stderr=efhandle)
        except OSError:
            os.close(ifhandle)
            os.remove(ifname)
            os.close(ofhandle)
            os.remove(ofname)
            os.close(efhandle)
            os.remove(efname)
        self.assertFalse(os.path.exists(ifname))
        self.assertFalse(os.path.exists(ofname))
        self.assertFalse(os.path.exists(efname))


# context manager
class _SuppressCoreFiles(object):
    """Try to prevent core files from being created."""
    old_limit = None

    def __enter__(self):
        """Try to save previous ulimit, then set it to (0, 0)."""
        try:
            import resource
            self.old_limit = resource.getrlimit(resource.RLIMIT_CORE)
            resource.setrlimit(resource.RLIMIT_CORE, (0, 0))
        except (ImportError, ValueError, resource.error):
            pass

        if sys.platform == 'darwin':
            # Check if the 'Crash Reporter' on OSX was configured
            # in 'Developer' mode and warn that it will get triggered
            # when it is.
            #
            # This assumes that this context manager is used in tests
            # that might trigger the next manager.
            value = subprocess.Popen(['/usr/bin/defaults', 'read',
                    'com.apple.CrashReporter', 'DialogType'],
                    stdout=subprocess.PIPE).communicate()[0]
            if value.strip() == b'developer':
                print("this tests triggers the Crash Reporter, "
                      "that is intentional", end='')
                sys.stdout.flush()

    def __exit__(self, *args):
        """Return core file behavior to default."""
        if self.old_limit is None:
            return
        try:
            import resource
            resource.setrlimit(resource.RLIMIT_CORE, self.old_limit)
        except (ImportError, ValueError, resource.error):
            pass


@unittest.skipIf(mswindows, "POSIX specific tests")
class POSIXProcessTestCase(BaseTestCase):

    def test_exceptions(self):
        nonexistent_dir = "/_this/pa.th/does/not/exist"
        try:
            os.chdir(nonexistent_dir)
        except OSError as e:
            # This avoids hard coding the errno value or the OS perror()
            # string and instead capture the exception that we want to see
            # below for comparison.
            desired_exception = e
        else:
            self.fail("chdir to nonexistant directory %s succeeded." %
                      nonexistent_dir)

        # Error in the child re-raised in the parent.
        try:
            p = subprocess.Popen([sys.executable, "-c", ""],
                                 cwd=nonexistent_dir)
        except OSError as e:
            # Test that the child process chdir failure actually makes
            # it up to the parent process as the correct exception.
            self.assertEqual(desired_exception.errno, e.errno)
            self.assertEqual(desired_exception.strerror, e.strerror)
        else:
            self.fail("Expected OSError: %s" % desired_exception)

    def test_restore_signals(self):
        # Code coverage for both values of restore_signals to make sure it
        # at least does not blow up.
        # A test for behavior would be complex.  Contributions welcome.
        subprocess.call([sys.executable, "-c", ""], restore_signals=True)
        subprocess.call([sys.executable, "-c", ""], restore_signals=False)

    def test_start_new_session(self):
        # For code coverage of calling setsid().  We don't care if we get an
        # EPERM error from it depending on the test execution environment, that
        # still indicates that it was called.
        try:
            output = subprocess.check_output(
                    [sys.executable, "-c",
                     "import os; print(os.getpgid(os.getpid()))"],
                    start_new_session=True)
        except OSError as e:
            if e.errno != errno.EPERM:
                raise
        else:
            parent_pgid = os.getpgid(os.getpid())
            child_pgid = int(output)
            self.assertNotEqual(parent_pgid, child_pgid)

    def test_run_abort(self):
        # returncode handles signal termination
        with _SuppressCoreFiles():
            p = subprocess.Popen([sys.executable, "-c",
                                  'import os; os.abort()'])
            p.wait()
        self.assertEqual(-p.returncode, signal.SIGABRT)

    def test_preexec(self):
        # DISCLAIMER: Setting environment variables is *not* a good use
        # of a preexec_fn.  This is merely a test.
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys,os;'
                              'sys.stdout.write(os.getenv("FRUIT"))'],
                             stdout=subprocess.PIPE,
                             preexec_fn=lambda: os.putenv("FRUIT", "apple"))
        self.assertEqual(p.stdout.read(), b"apple")

    def test_preexec_exception(self):
        def raise_it():
            raise ValueError("What if two swallows carried a coconut?")
        try:
            p = subprocess.Popen([sys.executable, "-c", ""],
                                 preexec_fn=raise_it)
        except RuntimeError as e:
            self.assertTrue(
                    subprocess._posixsubprocess,
                    "Expected a ValueError from the preexec_fn")
        except ValueError as e:
            self.assertIn("coconut", e.args[0])
        else:
            self.fail("Exception raised by preexec_fn did not make it "
                      "to the parent process.")

    @unittest.skipUnless(gc, "Requires a gc module.")
    def test_preexec_gc_module_failure(self):
        # This tests the code that disables garbage collection if the child
        # process will execute any Python.
        def raise_runtime_error():
            raise RuntimeError("this shouldn't escape")
        enabled = gc.isenabled()
        orig_gc_disable = gc.disable
        orig_gc_isenabled = gc.isenabled
        try:
            gc.disable()
            self.assertFalse(gc.isenabled())
            subprocess.call([sys.executable, '-c', ''],
                            preexec_fn=lambda: None)
            self.assertFalse(gc.isenabled(),
                             "Popen enabled gc when it shouldn't.")

            gc.enable()
            self.assertTrue(gc.isenabled())
            subprocess.call([sys.executable, '-c', ''],
                            preexec_fn=lambda: None)
            self.assertTrue(gc.isenabled(), "Popen left gc disabled.")

            gc.disable = raise_runtime_error
            self.assertRaises(RuntimeError, subprocess.Popen,
                              [sys.executable, '-c', ''],
                              preexec_fn=lambda: None)

            del gc.isenabled  # force an AttributeError
            self.assertRaises(AttributeError, subprocess.Popen,
                              [sys.executable, '-c', ''],
                              preexec_fn=lambda: None)
        finally:
            gc.disable = orig_gc_disable
            gc.isenabled = orig_gc_isenabled
            if not enabled:
                gc.disable()

    def test_args_string(self):
        # args is a string
        fd, fname = mkstemp()
        # reopen in text mode
        with open(fd, "w") as fobj:
            fobj.write("#!/bin/sh\n")
            fobj.write("exec '%s' -c 'import sys; sys.exit(47)'\n" %
                       sys.executable)
        os.chmod(fname, 0o700)
        p = subprocess.Popen(fname)
        p.wait()
        os.remove(fname)
        self.assertEqual(p.returncode, 47)

    def test_invalid_args(self):
        # invalid arguments should raise ValueError
        self.assertRaises(ValueError, subprocess.call,
                          [sys.executable, "-c",
                           "import sys; sys.exit(47)"],
                          startupinfo=47)
        self.assertRaises(ValueError, subprocess.call,
                          [sys.executable, "-c",
                           "import sys; sys.exit(47)"],
                          creationflags=47)

    def test_shell_sequence(self):
        # Run command through the shell (sequence)
        newenv = os.environ.copy()
        newenv["FRUIT"] = "apple"
        p = subprocess.Popen(["echo $FRUIT"], shell=1,
                             stdout=subprocess.PIPE,
                             env=newenv)
        self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")

    def test_shell_string(self):
        # Run command through the shell (string)
        newenv = os.environ.copy()
        newenv["FRUIT"] = "apple"
        p = subprocess.Popen("echo $FRUIT", shell=1,
                             stdout=subprocess.PIPE,
                             env=newenv)
        self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")

    def test_call_string(self):
        # call() function with string argument on UNIX
        fd, fname = mkstemp()
        # reopen in text mode
        with open(fd, "w") as fobj:
            fobj.write("#!/bin/sh\n")
            fobj.write("exec '%s' -c 'import sys; sys.exit(47)'\n" %
                       sys.executable)
        os.chmod(fname, 0o700)
        rc = subprocess.call(fname)
        os.remove(fname)
        self.assertEqual(rc, 47)

    def test_specific_shell(self):
        # Issue #9265: Incorrect name passed as arg[0].
        shells = []
        for prefix in ['/bin', '/usr/bin/', '/usr/local/bin']:
            for name in ['bash', 'ksh']:
                sh = os.path.join(prefix, name)
                if os.path.isfile(sh):
                    shells.append(sh)
        if not shells: # Will probably work for any shell but csh.
            self.skipTest("bash or ksh required for this test")
        sh = '/bin/sh'
        if os.path.isfile(sh) and not os.path.islink(sh):
            # Test will fail if /bin/sh is a symlink to csh.
            shells.append(sh)
        for sh in shells:
            p = subprocess.Popen("echo $0", executable=sh, shell=True,
                                 stdout=subprocess.PIPE)
            self.assertEqual(p.stdout.read().strip(), bytes(sh, 'ascii'))

    def _kill_process(self, method, *args):
        # Do not inherit file handles from the parent.
        # It should fix failures on some platforms.
        p = subprocess.Popen([sys.executable, "-c", """if 1:
                             import sys, time
                             sys.stdout.write('x\\n')
                             sys.stdout.flush()
                             time.sleep(30)
                             """],
                             close_fds=True,
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        # Wait for the interpreter to be completely initialized before
        # sending any signal.
        p.stdout.read(1)
        getattr(p, method)(*args)
        return p

    def test_send_signal(self):
        p = self._kill_process('send_signal', signal.SIGINT)
        _, stderr = p.communicate()
        self.assertIn(b'KeyboardInterrupt', stderr)
        self.assertNotEqual(p.wait(), 0)

    def test_kill(self):
        p = self._kill_process('kill')
        _, stderr = p.communicate()
        self.assertStderrEqual(stderr, b'')
        self.assertEqual(p.wait(), -signal.SIGKILL)

    def test_terminate(self):
        p = self._kill_process('terminate')
        _, stderr = p.communicate()
        self.assertStderrEqual(stderr, b'')
        self.assertEqual(p.wait(), -signal.SIGTERM)

    def test_surrogates_error_message(self):
        def prepare():
            raise ValueError("surrogate:\uDCff")

        try:
            subprocess.call(
                [sys.executable, "-c", "pass"],
                preexec_fn=prepare)
        except ValueError as err:
            # Pure Python implementations keeps the message
            self.assertIsNone(subprocess._posixsubprocess)
            self.assertEqual(str(err), "surrogate:\uDCff")
        except RuntimeError as err:
            # _posixsubprocess uses a default message
            self.assertIsNotNone(subprocess._posixsubprocess)
            self.assertEqual(str(err), "Exception occurred in preexec_fn.")
        else:
            self.fail("Expected ValueError or RuntimeError")

    def test_undecodable_env(self):
        for key, value in (('test', 'abc\uDCFF'), ('test\uDCFF', '42')):
            # test str with surrogates
            script = "import os; print(ascii(os.getenv(%s)))" % repr(key)
            env = os.environ.copy()
            env[key] = value
            # Force surrogate-escaping of \xFF in the child process;
            # otherwise it can be decoded as-is if the default locale
            # is latin-1.
            env['PYTHONFSENCODING'] = 'ascii'
            stdout = subprocess.check_output(
                [sys.executable, "-c", script],
                env=env)
            stdout = stdout.rstrip(b'\n\r')
            self.assertEquals(stdout.decode('ascii'), ascii(value))

            # test bytes
            key = key.encode("ascii", "surrogateescape")
            value = value.encode("ascii", "surrogateescape")
            script = "import os; print(ascii(os.getenvb(%s)))" % repr(key)
            env = os.environ.copy()
            env[key] = value
            stdout = subprocess.check_output(
                [sys.executable, "-c", script],
                env=env)
            stdout = stdout.rstrip(b'\n\r')
            self.assertEquals(stdout.decode('ascii'), ascii(value))

    def test_bytes_program(self):
        abs_program = os.fsencode(sys.executable)
        path, program = os.path.split(sys.executable)
        program = os.fsencode(program)

        # absolute bytes path
        exitcode = subprocess.call([abs_program, "-c", "pass"])
        self.assertEquals(exitcode, 0)

        # bytes program, unicode PATH
        env = os.environ.copy()
        env["PATH"] = path
        exitcode = subprocess.call([program, "-c", "pass"], env=env)
        self.assertEquals(exitcode, 0)

        # bytes program, bytes PATH
        envb = os.environb.copy()
        envb[b"PATH"] = os.fsencode(path)
        exitcode = subprocess.call([program, "-c", "pass"], env=envb)
        self.assertEquals(exitcode, 0)


@unittest.skipUnless(mswindows, "Windows specific tests")
class Win32ProcessTestCase(BaseTestCase):

    def test_startupinfo(self):
        # startupinfo argument
        # We uses hardcoded constants, because we do not want to
        # depend on win32all.
        STARTF_USESHOWWINDOW = 1
        SW_MAXIMIZE = 3
        startupinfo = subprocess.STARTUPINFO()
        startupinfo.dwFlags = STARTF_USESHOWWINDOW
        startupinfo.wShowWindow = SW_MAXIMIZE
        # Since Python is a console process, it won't be affected
        # by wShowWindow, but the argument should be silently
        # ignored
        subprocess.call([sys.executable, "-c", "import sys; sys.exit(0)"],
                        startupinfo=startupinfo)

    def test_creationflags(self):
        # creationflags argument
        CREATE_NEW_CONSOLE = 16
        sys.stderr.write("    a DOS box should flash briefly ...\n")
        subprocess.call(sys.executable +
                        ' -c "import time; time.sleep(0.25)"',
                        creationflags=CREATE_NEW_CONSOLE)

    def test_invalid_args(self):
        # invalid arguments should raise ValueError
        self.assertRaises(ValueError, subprocess.call,
                          [sys.executable, "-c",
                           "import sys; sys.exit(47)"],
                          preexec_fn=lambda: 1)
        self.assertRaises(ValueError, subprocess.call,
                          [sys.executable, "-c",
                           "import sys; sys.exit(47)"],
                          stdout=subprocess.PIPE,
                          close_fds=True)

    def test_close_fds(self):
        # close file descriptors
        rc = subprocess.call([sys.executable, "-c",
                              "import sys; sys.exit(47)"],
                              close_fds=True)
        self.assertEqual(rc, 47)

    def test_shell_sequence(self):
        # Run command through the shell (sequence)
        newenv = os.environ.copy()
        newenv["FRUIT"] = "physalis"
        p = subprocess.Popen(["set"], shell=1,
                             stdout=subprocess.PIPE,
                             env=newenv)
        self.assertIn(b"physalis", p.stdout.read())

    def test_shell_string(self):
        # Run command through the shell (string)
        newenv = os.environ.copy()
        newenv["FRUIT"] = "physalis"
        p = subprocess.Popen("set", shell=1,
                             stdout=subprocess.PIPE,
                             env=newenv)
        self.assertIn(b"physalis", p.stdout.read())

    def test_call_string(self):
        # call() function with string argument on Windows
        rc = subprocess.call(sys.executable +
                             ' -c "import sys; sys.exit(47)"')
        self.assertEqual(rc, 47)

    def _kill_process(self, method, *args):
        # Some win32 buildbot raises EOFError if stdin is inherited
        p = subprocess.Popen([sys.executable, "-c", """if 1:
                             import sys, time
                             sys.stdout.write('x\\n')
                             sys.stdout.flush()
                             time.sleep(30)
                             """],
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        # Wait for the interpreter to be completely initialized before
        # sending any signal.
        p.stdout.read(1)
        getattr(p, method)(*args)
        _, stderr = p.communicate()
        self.assertStderrEqual(stderr, b'')
        returncode = p.wait()
        self.assertNotEqual(returncode, 0)

    def test_send_signal(self):
        self._kill_process('send_signal', signal.SIGTERM)

    def test_kill(self):
        self._kill_process('kill')

    def test_terminate(self):
        self._kill_process('terminate')


# The module says:
#   "NB This only works (and is only relevant) for UNIX."
#
# Actually, getoutput should work on any platform with an os.popen, but
# I'll take the comment as given, and skip this suite.
@unittest.skipUnless(os.name == 'posix', "only relevant for UNIX")
class CommandTests(unittest.TestCase):
    def test_getoutput(self):
        self.assertEqual(subprocess.getoutput('echo xyzzy'), 'xyzzy')
        self.assertEqual(subprocess.getstatusoutput('echo xyzzy'),
                         (0, 'xyzzy'))

        # we use mkdtemp in the next line to create an empty directory
        # under our exclusive control; from that, we can invent a pathname
        # that we _know_ won't exist.  This is guaranteed to fail.
        dir = None
        try:
            dir = tempfile.mkdtemp()
            name = os.path.join(dir, "foo")

            status, output = subprocess.getstatusoutput('cat ' + name)
            self.assertNotEqual(status, 0)
        finally:
            if dir is not None:
                os.rmdir(dir)


@unittest.skipUnless(getattr(subprocess, '_has_poll', False),
                     "poll system call not supported")
class ProcessTestCaseNoPoll(ProcessTestCase):
    def setUp(self):
        subprocess._has_poll = False
        ProcessTestCase.setUp(self)

    def tearDown(self):
        subprocess._has_poll = True
        ProcessTestCase.tearDown(self)


@unittest.skipUnless(getattr(subprocess, '_posixsubprocess', False),
                     "_posixsubprocess extension module not found.")
class ProcessTestCasePOSIXPurePython(ProcessTestCase, POSIXProcessTestCase):
    def setUp(self):
        subprocess._posixsubprocess = None
        ProcessTestCase.setUp(self)
        POSIXProcessTestCase.setUp(self)

    def tearDown(self):
        subprocess._posixsubprocess = sys.modules['_posixsubprocess']
        POSIXProcessTestCase.tearDown(self)
        ProcessTestCase.tearDown(self)


class HelperFunctionTests(unittest.TestCase):
    @unittest.skipIf(mswindows, "errno and EINTR make no sense on windows")
    def test_eintr_retry_call(self):
        record_calls = []
        def fake_os_func(*args):
            record_calls.append(args)
            if len(record_calls) == 2:
                raise OSError(errno.EINTR, "fake interrupted system call")
            return tuple(reversed(args))

        self.assertEqual((999, 256),
                         subprocess._eintr_retry_call(fake_os_func, 256, 999))
        self.assertEqual([(256, 999)], record_calls)
        # This time there will be an EINTR so it will loop once.
        self.assertEqual((666,),
                         subprocess._eintr_retry_call(fake_os_func, 666))
        self.assertEqual([(256, 999), (666,), (666,)], record_calls)


@unittest.skipUnless(mswindows, "Windows-specific tests")
class CommandsWithSpaces (BaseTestCase):

    def setUp(self):
        super().setUp()
        f, fname = mkstemp(".py", "te st")
        self.fname = fname.lower ()
        os.write(f, b"import sys;"
                    b"sys.stdout.write('%d %s' % (len(sys.argv), [a.lower () for a in sys.argv]))"
        )
        os.close(f)

    def tearDown(self):
        os.remove(self.fname)
        super().tearDown()

    def with_spaces(self, *args, **kwargs):
        kwargs['stdout'] = subprocess.PIPE
        p = subprocess.Popen(*args, **kwargs)
        self.assertEqual(
          p.stdout.read ().decode("mbcs"),
          "2 [%r, 'ab cd']" % self.fname
        )

    def test_shell_string_with_spaces(self):
        # call() function with string argument with spaces on Windows
        self.with_spaces('"%s" "%s" "%s"' % (sys.executable, self.fname,
                                             "ab cd"), shell=1)

    def test_shell_sequence_with_spaces(self):
        # call() function with sequence argument with spaces on Windows
        self.with_spaces([sys.executable, self.fname, "ab cd"], shell=1)

    def test_noshell_string_with_spaces(self):
        # call() function with string argument with spaces on Windows
        self.with_spaces('"%s" "%s" "%s"' % (sys.executable, self.fname,
                             "ab cd"))

    def test_noshell_sequence_with_spaces(self):
        # call() function with sequence argument with spaces on Windows
        self.with_spaces([sys.executable, self.fname, "ab cd"])

def test_main():
    unit_tests = (ProcessTestCase,
                  POSIXProcessTestCase,
                  Win32ProcessTestCase,
                  ProcessTestCasePOSIXPurePython,
                  CommandTests,
                  ProcessTestCaseNoPoll,
                  HelperFunctionTests,
                  CommandsWithSpaces)

    support.run_unittest(*unit_tests)
    support.reap_children()

if __name__ == "__main__":
    test_main()