### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](pwd.xhtml "pwd --- 用户密码数据库") | - [上一页](unix.xhtml "Unix 专有服务") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [Unix 专有服务](unix.xhtml) » - $('.inline-search').show(0); | # [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)") --- The most common POSIX system calls - - - - - - This module provides access to operating system functionality that is standardized by the C Standard and the POSIX standard (a thinly disguised Unix interface). **Do not import this module directly.** Instead, import the module [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces."), which provides a *portable* version of this interface. On Unix, the [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.")module provides a superset of the [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)") interface. On non-Unix operating systems the [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)") module is not available, but a subset is always available through the [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") interface. Once [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") is imported, there is *no* performance penalty in using it instead of [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)"). In addition, [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") provides some additional functionality, such as automatically calling [`putenv()`](os.xhtml#os.putenv "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 [`OSError`](exceptions.xhtml#OSError "OSError"). ## Large File Support 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 `int` and `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 *large files*. Large file support is enabled in Python when the size of an `off_t` is larger than a `long` and the `long long` type is available and is at least as large as an `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 [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") module documentation, [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)") defines the following data item: `posix.``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 [`execv()`](os.xhtml#os.execv "os.execv"), [`popen()`](os.xhtml#os.popen "os.popen") or [`system()`](os.xhtml#os.system "os.system"); if you need to change the environment, pass `environ` to [`execve()`](os.xhtml#os.execve "os.execve") or add variable assignments and export statements to the command string for [`system()`](os.xhtml#os.system "os.system") or [`popen()`](os.xhtml#os.popen "os.popen"). 在 3.2 版更改: On Unix, keys and values are bytes. 注解 The [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") module provides an alternate implementation of `environ`which updates the environment on modification. Note also that updating [`os.environ`](os.xhtml#os.environ "os.environ") will render this dictionary obsolete. Use of the [`os`](os.xhtml#module-os "os: Miscellaneous operating system interfaces.") module version of this is recommended over direct access to the [`posix`](#module-posix "posix: The most common POSIX system calls (normally used via module os). (Unix)") module. ### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](pwd.xhtml "pwd --- 用户密码数据库") | - [上一页](unix.xhtml "Unix 专有服务") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [Unix 专有服务](unix.xhtml) » - $('.inline-search').show(0); | © [版权所有](../copyright.xhtml) 2001-2019, Python Software Foundation. Python 软件基金会是一个非盈利组织。 [请捐助。](https://www.python.org/psf/donations/) 最后更新于 5月 21, 2019. [发现了问题](../bugs.xhtml)？ 使用[Sphinx](http://sphinx.pocoo.org/)1.8.4 创建。