mirror of
https://github.com/python/cpython.git
synced 2025-01-10 18:44:53 +08:00
68dbebc8e8
svn+ssh://pythondev@svn.python.org/python/branches/py3k
................
r77167 | benjamin.peterson | 2009-12-30 21:11:23 -0600 (Wed, 30 Dec 2009) | 61 lines
Merged revisions 76847,76851,76869,76882,76891-76892,76924,77007,77070,77092,77096,77120,77126,77155 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r76847 | benjamin.peterson | 2009-12-14 21:25:27 -0600 (Mon, 14 Dec 2009) | 1 line
adverb
........
r76851 | benjamin.peterson | 2009-12-15 21:28:52 -0600 (Tue, 15 Dec 2009) | 1 line
remove lib2to3 resource
........
r76869 | vinay.sajip | 2009-12-17 08:52:00 -0600 (Thu, 17 Dec 2009) | 1 line
Issue #7529: logging: Minor correction to documentation.
........
r76882 | georg.brandl | 2009-12-19 11:30:28 -0600 (Sat, 19 Dec 2009) | 1 line
#7527: use standard versionadded tags.
........
r76891 | georg.brandl | 2009-12-19 12:16:31 -0600 (Sat, 19 Dec 2009) | 1 line
#7479: add note about function availability on Unices.
........
r76892 | georg.brandl | 2009-12-19 12:20:18 -0600 (Sat, 19 Dec 2009) | 1 line
#7480: remove tautology.
........
r76924 | georg.brandl | 2009-12-20 08:28:05 -0600 (Sun, 20 Dec 2009) | 1 line
Small indentation fix.
........
r77007 | gregory.p.smith | 2009-12-23 03:31:11 -0600 (Wed, 23 Dec 2009) | 3 lines
Fix possible integer overflow in lchown and fchown functions. For issue1747858.
........
r77070 | amaury.forgeotdarc | 2009-12-27 14:06:44 -0600 (Sun, 27 Dec 2009) | 2 lines
Fix a typo in comment
........
r77092 | georg.brandl | 2009-12-28 02:48:24 -0600 (Mon, 28 Dec 2009) | 1 line
#7404: remove reference to non-existing example files.
........
r77096 | benjamin.peterson | 2009-12-28 14:51:17 -0600 (Mon, 28 Dec 2009) | 1 line
document new fix_callable behavior
........
r77120 | georg.brandl | 2009-12-29 15:09:17 -0600 (Tue, 29 Dec 2009) | 1 line
#7595: fix typo in argument default constant.
........
r77126 | amaury.forgeotdarc | 2009-12-29 17:06:17 -0600 (Tue, 29 Dec 2009) | 2 lines
#7579: Add docstrings to the msvcrt module
........
r77155 | georg.brandl | 2009-12-30 13:03:00 -0600 (Wed, 30 Dec 2009) | 1 line
We only support Windows NT derivatives now.
........
................
434 lines
20 KiB
ReStructuredText
434 lines
20 KiB
ReStructuredText
|
|
:mod:`select` --- Waiting for I/O completion
|
|
============================================
|
|
|
|
.. module:: select
|
|
:synopsis: Wait for I/O completion on multiple streams.
|
|
|
|
|
|
This module provides access to the :cfunc:`select` and :cfunc:`poll` functions
|
|
available in most operating systems, :cfunc:`epoll` available on Linux 2.5+ and
|
|
:cfunc:`kqueue` available on most BSD.
|
|
Note that on Windows, it only works for sockets; on other operating systems,
|
|
it also works for other file types (in particular, on Unix, it works on pipes).
|
|
It cannot be used on regular files to determine whether a file has grown since
|
|
it was last read.
|
|
|
|
The module defines the following:
|
|
|
|
|
|
.. exception:: error
|
|
|
|
The exception raised when an error occurs. The accompanying value is a pair
|
|
containing the numeric error code from :cdata:`errno` and the corresponding
|
|
string, as would be printed by the C function :cfunc:`perror`.
|
|
|
|
|
|
.. function:: epoll([sizehint=-1])
|
|
|
|
(Only supported on Linux 2.5.44 and newer.) Returns an edge polling object,
|
|
which can be used as Edge or Level Triggered interface for I/O events; see
|
|
section :ref:`epoll-objects` below for the methods supported by epolling
|
|
objects.
|
|
|
|
|
|
.. function:: poll()
|
|
|
|
(Not supported by all operating systems.) Returns a polling object, which
|
|
supports registering and unregistering file descriptors, and then polling them
|
|
for I/O events; see section :ref:`poll-objects` below for the methods supported
|
|
by polling objects.
|
|
|
|
|
|
.. function:: kqueue()
|
|
|
|
(Only supported on BSD.) Returns a kernel queue object object; see section
|
|
:ref:`kqueue-objects` below for the methods supported by kqueue objects.
|
|
|
|
|
|
.. function:: kevent(ident, filter=KQ_FILTER_READ, flags=KQ_EV_ADD, fflags=0, data=0, udata=0)
|
|
|
|
(Only supported on BSD.) Returns a kernel event object object; see section
|
|
:ref:`kevent-objects` below for the methods supported by kqueue objects.
|
|
|
|
|
|
.. function:: select(rlist, wlist, xlist[, timeout])
|
|
|
|
This is a straightforward interface to the Unix :cfunc:`select` system call.
|
|
The first three arguments are sequences of 'waitable objects': either
|
|
integers representing file descriptors or objects with a parameterless method
|
|
named :meth:`fileno` returning such an integer:
|
|
|
|
* *rlist*: wait until ready for reading
|
|
* *wlist*: wait until ready for writing
|
|
* *xlist*: wait for an "exceptional condition" (see the manual page for what
|
|
your system considers such a condition)
|
|
|
|
Empty sequences are allowed, but acceptance of three empty sequences is
|
|
platform-dependent. (It is known to work on Unix but not on Windows.) The
|
|
optional *timeout* argument specifies a time-out as a floating point number
|
|
in seconds. When the *timeout* argument is omitted the function blocks until
|
|
at least one file descriptor is ready. A time-out value of zero specifies a
|
|
poll and never blocks.
|
|
|
|
The return value is a triple of lists of objects that are ready: subsets of the
|
|
first three arguments. When the time-out is reached without a file descriptor
|
|
becoming ready, three empty lists are returned.
|
|
|
|
.. index::
|
|
single: socket() (in module socket)
|
|
single: popen() (in module os)
|
|
|
|
Among the acceptable object types in the sequences are Python file objects (e.g.
|
|
``sys.stdin``, or objects returned by :func:`open` or :func:`os.popen`), socket
|
|
objects returned by :func:`socket.socket`. You may also define a :dfn:`wrapper`
|
|
class yourself, as long as it has an appropriate :meth:`fileno` method (that
|
|
really returns a file descriptor, not just a random integer).
|
|
|
|
.. note::
|
|
|
|
.. index:: single: WinSock
|
|
|
|
File objects on Windows are not acceptable, but sockets are. On Windows,
|
|
the underlying :cfunc:`select` function is provided by the WinSock
|
|
library, and does not handle file descriptors that don't originate from
|
|
WinSock.
|
|
|
|
|
|
.. _epoll-objects:
|
|
|
|
Edge and Level Trigger Polling (epoll) Objects
|
|
----------------------------------------------
|
|
|
|
http://linux.die.net/man/4/epoll
|
|
|
|
*eventmask*
|
|
|
|
+-----------------------+-----------------------------------------------+
|
|
| Constant | Meaning |
|
|
+=======================+===============================================+
|
|
| :const:`EPOLLIN` | Available for read |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLOUT` | Available for write |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLPRI` | Urgent data for read |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLERR` | Error condition happened on the assoc. fd |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLHUP` | Hang up happened on the assoc. fd |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLET` | Set Edge Trigger behavior, the default is |
|
|
| | Level Trigger behavior |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLONESHOT` | Set one-shot behavior. After one event is |
|
|
| | pulled out, the fd is internally disabled |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLRDNORM` | ??? |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLRDBAND` | ??? |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLWRNORM` | ??? |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLWRBAND` | ??? |
|
|
+-----------------------+-----------------------------------------------+
|
|
| :const:`EPOLLMSG` | ??? |
|
|
+-----------------------+-----------------------------------------------+
|
|
|
|
|
|
.. method:: epoll.close()
|
|
|
|
Close the control file descriptor of the epoll object.
|
|
|
|
|
|
.. method:: epoll.fileno()
|
|
|
|
Return the file descriptor number of the control fd.
|
|
|
|
|
|
.. method:: epoll.fromfd(fd)
|
|
|
|
Create an epoll object from a given file descriptor.
|
|
|
|
|
|
.. method:: epoll.register(fd[, eventmask])
|
|
|
|
Register a fd descriptor with the epoll object.
|
|
|
|
.. note::
|
|
|
|
Registering a file descriptor that's already registered raises an
|
|
IOError -- contrary to :ref:`poll-objects`'s register.
|
|
|
|
|
|
.. method:: epoll.modify(fd, eventmask)
|
|
|
|
Modify a register file descriptor.
|
|
|
|
|
|
.. method:: epoll.unregister(fd)
|
|
|
|
Remove a registered file descriptor from the epoll object.
|
|
|
|
|
|
.. method:: epoll.poll([timeout=-1[, maxevents=-1]])
|
|
|
|
Wait for events. timeout in seconds (float)
|
|
|
|
|
|
.. _poll-objects:
|
|
|
|
Polling Objects
|
|
---------------
|
|
|
|
The :cfunc:`poll` system call, supported on most Unix systems, provides better
|
|
scalability for network servers that service many, many clients at the same
|
|
time. :cfunc:`poll` scales better because the system call only requires listing
|
|
the file descriptors of interest, while :cfunc:`select` builds a bitmap, turns
|
|
on bits for the fds of interest, and then afterward the whole bitmap has to be
|
|
linearly scanned again. :cfunc:`select` is O(highest file descriptor), while
|
|
:cfunc:`poll` is O(number of file descriptors).
|
|
|
|
|
|
.. method:: poll.register(fd[, eventmask])
|
|
|
|
Register a file descriptor with the polling object. Future calls to the
|
|
:meth:`poll` method will then check whether the file descriptor has any pending
|
|
I/O events. *fd* can be either an integer, or an object with a :meth:`fileno`
|
|
method that returns an integer. File objects implement :meth:`fileno`, so they
|
|
can also be used as the argument.
|
|
|
|
*eventmask* is an optional bitmask describing the type of events you want to
|
|
check for, and can be a combination of the constants :const:`POLLIN`,
|
|
:const:`POLLPRI`, and :const:`POLLOUT`, described in the table below. If not
|
|
specified, the default value used will check for all 3 types of events.
|
|
|
|
+-------------------+------------------------------------------+
|
|
| Constant | Meaning |
|
|
+===================+==========================================+
|
|
| :const:`POLLIN` | There is data to read |
|
|
+-------------------+------------------------------------------+
|
|
| :const:`POLLPRI` | There is urgent data to read |
|
|
+-------------------+------------------------------------------+
|
|
| :const:`POLLOUT` | Ready for output: writing will not block |
|
|
+-------------------+------------------------------------------+
|
|
| :const:`POLLERR` | Error condition of some sort |
|
|
+-------------------+------------------------------------------+
|
|
| :const:`POLLHUP` | Hung up |
|
|
+-------------------+------------------------------------------+
|
|
| :const:`POLLNVAL` | Invalid request: descriptor not open |
|
|
+-------------------+------------------------------------------+
|
|
|
|
Registering a file descriptor that's already registered is not an error, and has
|
|
the same effect as registering the descriptor exactly once.
|
|
|
|
|
|
.. method:: poll.modify(fd, eventmask)
|
|
|
|
Modifies an already registered fd. This has the same effect as
|
|
:meth:`register(fd, eventmask)`. Attempting to modify a file descriptor
|
|
that was never registered causes an :exc:`IOError` exception with errno
|
|
:const:`ENOENT` to be raised.
|
|
|
|
|
|
.. method:: poll.unregister(fd)
|
|
|
|
Remove a file descriptor being tracked by a polling object. Just like the
|
|
:meth:`register` method, *fd* can be an integer or an object with a
|
|
:meth:`fileno` method that returns an integer.
|
|
|
|
Attempting to remove a file descriptor that was never registered causes a
|
|
:exc:`KeyError` exception to be raised.
|
|
|
|
|
|
.. method:: poll.poll([timeout])
|
|
|
|
Polls the set of registered file descriptors, and returns a possibly-empty list
|
|
containing ``(fd, event)`` 2-tuples for the descriptors that have events or
|
|
errors to report. *fd* is the file descriptor, and *event* is a bitmask with
|
|
bits set for the reported events for that descriptor --- :const:`POLLIN` for
|
|
waiting input, :const:`POLLOUT` to indicate that the descriptor can be written
|
|
to, and so forth. An empty list indicates that the call timed out and no file
|
|
descriptors had any events to report. If *timeout* is given, it specifies the
|
|
length of time in milliseconds which the system will wait for events before
|
|
returning. If *timeout* is omitted, negative, or :const:`None`, the call will
|
|
block until there is an event for this poll object.
|
|
|
|
|
|
.. _kqueue-objects:
|
|
|
|
Kqueue Objects
|
|
--------------
|
|
|
|
.. method:: kqueue.close()
|
|
|
|
Close the control file descriptor of the kqueue object.
|
|
|
|
|
|
.. method:: kqueue.fileno()
|
|
|
|
Return the file descriptor number of the control fd.
|
|
|
|
|
|
.. method:: kqueue.fromfd(fd)
|
|
|
|
Create a kqueue object from a given file descriptor.
|
|
|
|
|
|
.. method:: kqueue.control(changelist, max_events[, timeout=None]) -> eventlist
|
|
|
|
Low level interface to kevent
|
|
|
|
- changelist must be an iterable of kevent object or None
|
|
- max_events must be 0 or a positive integer
|
|
- timeout in seconds (floats possible)
|
|
|
|
|
|
.. _kevent-objects:
|
|
|
|
Kevent Objects
|
|
--------------
|
|
|
|
http://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
|
|
|
|
.. attribute:: kevent.ident
|
|
|
|
Value used to identify the event. The interpretation depends on the filter
|
|
but it's usually the file descriptor. In the constructor ident can either
|
|
be an int or an object with a fileno() function. kevent stores the integer
|
|
internally.
|
|
|
|
.. attribute:: kevent.filter
|
|
|
|
Name of the kernel filter.
|
|
|
|
+---------------------------+---------------------------------------------+
|
|
| Constant | Meaning |
|
|
+===========================+=============================================+
|
|
| :const:`KQ_FILTER_READ` | Takes a descriptor and returns whenever |
|
|
| | there is data available to read |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_WRITE` | Takes a descriptor and returns whenever |
|
|
| | there is data available to write |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_AIO` | AIO requests |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_VNODE` | Returns when one or more of the requested |
|
|
| | events watched in *fflag* occurs |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_PROC` | Watch for events on a process id |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_NETDEV` | Watch for events on a network device |
|
|
| | [not available on Mac OS X] |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_SIGNAL` | Returns whenever the watched signal is |
|
|
| | delivered to the process |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_FILTER_TIMER` | Establishes an arbitrary timer |
|
|
+---------------------------+---------------------------------------------+
|
|
|
|
.. attribute:: kevent.flags
|
|
|
|
Filter action.
|
|
|
|
+---------------------------+---------------------------------------------+
|
|
| Constant | Meaning |
|
|
+===========================+=============================================+
|
|
| :const:`KQ_EV_ADD` | Adds or modifies an event |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_DELETE` | Removes an event from the queue |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_ENABLE` | Permitscontrol() to returns the event |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_DISABLE` | Disablesevent |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_ONESHOT` | Removes event after first occurrence |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_CLEAR` | Reset the state after an event is retrieved |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_SYSFLAGS` | internal event |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_FLAG1` | internal event |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_EOF` | Filter specific EOF condition |
|
|
+---------------------------+---------------------------------------------+
|
|
| :const:`KQ_EV_ERROR` | See return values |
|
|
+---------------------------+---------------------------------------------+
|
|
|
|
|
|
.. attribute:: kevent.fflags
|
|
|
|
Filter specific flags.
|
|
|
|
:const:`KQ_FILTER_READ` and :const:`KQ_FILTER_WRITE` filter flags:
|
|
|
|
+----------------------------+--------------------------------------------+
|
|
| Constant | Meaning |
|
|
+============================+============================================+
|
|
| :const:`KQ_NOTE_LOWAT` | low water mark of a socket buffer |
|
|
+----------------------------+--------------------------------------------+
|
|
|
|
:const:`KQ_FILTER_VNODE` filter flags:
|
|
|
|
+----------------------------+--------------------------------------------+
|
|
| Constant | Meaning |
|
|
+============================+============================================+
|
|
| :const:`KQ_NOTE_DELETE` | *unlink()* was called |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_WRITE` | a write occurred |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_EXTEND` | the file was extended |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_ATTRIB` | an attribute was changed |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_LINK` | the link count has changed |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_RENAME` | the file was renamed |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_REVOKE` | access to the file was revoked |
|
|
+----------------------------+--------------------------------------------+
|
|
|
|
:const:`KQ_FILTER_PROC` filter flags:
|
|
|
|
+----------------------------+--------------------------------------------+
|
|
| Constant | Meaning |
|
|
+============================+============================================+
|
|
| :const:`KQ_NOTE_EXIT` | the process has exited |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_FORK` | the process has called *fork()* |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_EXEC` | the process has executed a new process |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_PCTRLMASK` | internal filter flag |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_PDATAMASK` | internal filter flag |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_TRACK` | follow a process across *fork()* |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_CHILD` | returned on the child process for |
|
|
| | *NOTE_TRACK* |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_TRACKERR` | unable to attach to a child |
|
|
+----------------------------+--------------------------------------------+
|
|
|
|
:const:`KQ_FILTER_NETDEV` filter flags (not available on Mac OS X):
|
|
|
|
+----------------------------+--------------------------------------------+
|
|
| Constant | Meaning |
|
|
+============================+============================================+
|
|
| :const:`KQ_NOTE_LINKUP` | link is up |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_LINKDOWN` | link is down |
|
|
+----------------------------+--------------------------------------------+
|
|
| :const:`KQ_NOTE_LINKINV` | link state is invalid |
|
|
+----------------------------+--------------------------------------------+
|
|
|
|
|
|
.. attribute:: kevent.data
|
|
|
|
Filter specific data.
|
|
|
|
|
|
.. attribute:: kevent.udata
|
|
|
|
User defined value.
|