This module defines one class called :class:`Popen`:
-.. class:: Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=_PLATFORM_DEFAULT, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False)
+.. class:: Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=True, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False, pass_fds=())
Arguments are:
If *close_fds* is true, all file descriptors except :const:`0`, :const:`1` and
:const:`2` will be closed before the child process is executed. (Unix only).
- The default varies by platform: :const:`False` on Windows and :const:`True`
- on POSIX and other platforms.
+ The default varies by platform: Always true on Unix. On Windows it is
+ true when *stdin*/*stdout*/*stderr* are :const:`None`, false otherwise.
On Windows, if *close_fds* is true then no handles will be inherited by the
child process. Note that on Windows, you cannot set *close_fds* to true and
also redirect the standard handles by setting *stdin*, *stdout* or *stderr*.
-.. versionchanged:: 3.2
- The default was changed to True on non Windows platforms.
+ .. versionchanged:: 3.2
+ The default for *close_fds* was changed from :const:`False` to
+ what is described above.
+
+ *pass_fds* is an optional sequence of file descriptors to keep open
+ between the parent and child. Providing any *pass_fds* forces
+ *close_fds* to be :const:`True`. (Unix only)
+
+ .. versionadded:: 3.2
+ The *pass_fds* parameter was added.
If *cwd* is not ``None``, the child's current directory will be changed to *cwd*
before it is executed. Note that this directory is not considered when
class Popen(args, bufsize=0, executable=None,
stdin=None, stdout=None, stderr=None,
- preexec_fn=None, close_fds=_PLATFORM_DEFAULT, shell=False,
+ preexec_fn=None, close_fds=True, shell=False,
cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0,
- restore_signals=True, start_new_session=False):
+ restore_signals=True, start_new_session=False, pass_fds=()):
Arguments are:
If close_fds is true, all file descriptors except 0, 1 and 2 will be
closed before the child process is executed. The default for close_fds
-varies by platform: False on Windows and True on all other platforms
-such as POSIX.
+varies by platform: Always true on POSIX. True when stdin/stdout/stderr
+are None on Windows, false otherwise.
+
+pass_fds is an optional sequence of file descriptors to keep open between the
+parent and child. Providing any pass_fds implicitly sets close_fds to true.
if shell is true, the specified command will be executed through the
shell.
return getstatusoutput(cmd)[1]
-if mswindows:
- _PLATFORM_DEFAULT = False
-else:
- _PLATFORM_DEFAULT = True
+_PLATFORM_DEFAULT_CLOSE_FDS = object()
class Popen(object):
def __init__(self, args, bufsize=0, executable=None,
stdin=None, stdout=None, stderr=None,
- preexec_fn=None, close_fds=_PLATFORM_DEFAULT, shell=False,
- cwd=None, env=None, universal_newlines=False,
+ preexec_fn=None, close_fds=_PLATFORM_DEFAULT_CLOSE_FDS,
+ shell=False, cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0,
restore_signals=True, start_new_session=False,
pass_fds=()):
if preexec_fn is not None:
raise ValueError("preexec_fn is not supported on Windows "
"platforms")
- if close_fds and (stdin is not None or stdout is not None or
- stderr is not None):
- raise ValueError("close_fds is not supported on Windows "
- "platforms if you redirect stdin/stdout/stderr")
+ any_stdio_set = (stdin is not None or stdout is not None or
+ stderr is not None)
+ if close_fds is _PLATFORM_DEFAULT_CLOSE_FDS:
+ if any_stdio_set:
+ close_fds = False
+ else:
+ close_fds = True
+ elif close_fds and any_stdio_set:
+ raise ValueError(
+ "close_fds is not supported on Windows platforms"
+ " if you redirect stdin/stdout/stderr")
else:
# POSIX
+ if close_fds is _PLATFORM_DEFAULT_CLOSE_FDS:
+ close_fds = True
+ if pass_fds and not close_fds:
+ warnings.warn("pass_fds overriding close_fds.", RuntimeWarning)
+ close_fds = True
if startupinfo is not None:
raise ValueError("startupinfo is only supported on Windows "
"platforms")
raise ValueError("creationflags is only supported on Windows "
"platforms")
- if pass_fds and not close_fds:
- raise ValueError("pass_fds requires close_fds=True.")
-
self.stdin = None
self.stdout = None
self.stderr = None
unused_restore_signals, unused_start_new_session):
"""Execute program (MS Windows version)"""
- assert not pass_fds, "pass_fds not yet supported on Windows"
+ assert not pass_fds, "pass_fds not supported on Windows."
if not isinstance(args, str):
args = list2cmdline(args)
# precondition: fds_to_keep must be sorted and unique
start_fd = 3
for fd in fds_to_keep:
- if fd > start_fd:
+ if fd >= start_fd:
os.closerange(start_fd, fd)
start_fd = fd + 1
if start_fd <= MAXFD:
"Some fds were left open")
self.assertIn(1, remaining_fds, "Subprocess failed")
+ def test_pass_fds(self):
+ fd_status = support.findfile("fd_status.py", subdir="subprocessdata")
+
+ open_fds = set()
+
+ for x in range(5):
+ fds = os.pipe()
+ self.addCleanup(os.close, fds[0])
+ self.addCleanup(os.close, fds[1])
+ open_fds.update(fds)
+
+ for fd in open_fds:
+ p = subprocess.Popen([sys.executable, fd_status],
+ stdout=subprocess.PIPE, close_fds=True,
+ pass_fds=(fd, ))
+ output, ignored = p.communicate()
+
+ remaining_fds = set(map(int, output.split(b',')))
+ to_be_closed = open_fds - {fd}
+
+ self.assertIn(fd, remaining_fds, "fd to be passed not passed")
+ self.assertFalse(remaining_fds & to_be_closed,
+ "fd to be closed passed")
+
+ # pass_fds overrides close_fds with a warning.
+ with self.assertWarns(RuntimeWarning) as context:
+ self.assertFalse(subprocess.call(
+ [sys.executable, "-c", "import sys; sys.exit(0)"],
+ close_fds=False, pass_fds=(fd, )))
+ self.assertIn('overriding close_fds', str(context.warning))
+
@unittest.skipUnless(mswindows, "Windows specific tests")
class Win32ProcessTestCase(BaseTestCase):
- Issue #10107: Warn about unsaved files in IDLE on OSX.
- Issue #7213: subprocess.Popen's default for close_fds has been changed.
- It is now platform specific, keeping its default of False on Windows and
- changing the default to True on POSIX and other platforms.
+ It is now True in most cases other than on Windows when input, output or
+ error handles are provided.
+
+- Issue #6559: subprocess.Popen has a new pass_fds parameter (actually
+ added in 3.2beta1) to allow specifying a specific list of file descriptors
+ to keep open in the child process.
What's New in Python 3.2 Beta 1?
errno = 0; /* We don't want to report an OSError. */
goto error;
}
- if (keep_fd <= start_fd)
+ if (keep_fd < start_fd)
continue;
for (fd_num = start_fd; fd_num < keep_fd; ++fd_num) {
close(fd_num);
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