:mod:`posix` --- The most common POSIX system calls

.. module:: posix
 :platform: Unix
 :synopsis: The most common POSIX system calls (normally used via module os).

This module provides access to operating system functionality that is standardized by the C Standard and the POSIX standard (a thinly disguised Unix interface).

.. index:: module: os

Do not import this module directly. Instead, import the module :mod:`os`, which provides a portable version of this interface. On Unix, the :mod:`os` module provides a superset of the :mod:`posix` interface. On non-Unix operating systems the :mod:`posix` module is not available, but a subset is always available through the :mod:`os` interface. Once :mod:`os` is imported, there is no performance penalty in using it instead of :mod:`posix`. In addition, :mod:`os` provides some additional functionality, such as automatically calling :func:`~os.putenv` when an entry in os.environ is changed.

Errors are reported as exceptions; the usual exceptions are given for type errors, while errors reported by the system calls raise :exc:`OSError`.

Large File Support

.. index::
 single: large files
 single: file; large files

.. sectionauthor:: Steve Clift <clift@mail.anacapa.net>

Several operating systems (including AIX, HP-UX, Irix and Solaris) provide support for files that are larger than 2 GiB from a C programming model where :c:type:`int` and :c:type:`long` are 32-bit values. This is typically accomplished by defining the relevant size and offset types as 64-bit values. Such files are sometimes referred to as :dfn:`large files`.

Large file support is enabled in Python when the size of an :c:type:`off_t` is larger than a :c:type:`long` and the :c:type:`long long` is at least as large as an :c:type:`off_t`. It may be necessary to configure and compile Python with certain compiler flags to enable this mode. For example, it is enabled by default with recent versions of Irix, but with Solaris 2.6 and 2.7 you need to do something like:

CFLAGS="`getconf LFS_CFLAGS`" OPT="-g -O2 $CFLAGS" \
 ./configure

On large-file-capable Linux systems, this might work:

CFLAGS='-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64' OPT="-g -O2 $CFLAGS" \
 ./configure

Notable Module Contents

In addition to many functions described in the :mod:`os` module documentation, :mod:`posix` defines the following data item:

.. data:: environ

 A dictionary representing the string environment at the time the interpreter
 was started. Keys and values are bytes on Unix and str on Windows. For
 example, ``environ[b'HOME']`` (``environ['HOME']`` on Windows) is the
 pathname of your home directory, equivalent to ``getenv("HOME")`` in C.

 Modifying this dictionary does not affect the string environment passed on by
 :func:`~os.execv`, :func:`~os.popen` or :func:`~os.system`; if you need to
 change the environment, pass ``environ`` to :func:`~os.execve` or add
 variable assignments and export statements to the command string for
 :func:`~os.system` or :func:`~os.popen`.

 .. versionchanged:: 3.2
 On Unix, keys and values are bytes.

 .. note::

 The :mod:`os` module provides an alternate implementation of ``environ``
 which updates the environment on modification. Note also that updating
 :data:`os.environ` will render this dictionary obsolete. Use of the
 :mod:`os` module version of this is recommended over direct access to the
 :mod:`posix` module.

此处可能存在不合适展示的内容,页面不予展示。您可通过相关编辑功能自查并修改。

如您确认内容无涉及 不当用语 / 纯广告导流 / 暴力 / 低俗色情 / 侵权 / 盗版 / 虚假 / 无价值内容或违法国家有关法律法规的内容,可点击提交进行申诉,我们将尽快为您处理。