mirror of
https://github.com/python/cpython.git
synced 2024-12-01 03:01:36 +01:00
82f355a36a
to use `getconf LFS_CFLAGS`. Steve Clift (the author of the section and large file support) agrees that this is the right thing to do.
91 lines
3.8 KiB
TeX
91 lines
3.8 KiB
TeX
\section{\module{posix} ---
|
|
The most common \POSIX{} system calls}
|
|
|
|
\declaremodule{builtin}{posix}
|
|
\platform{Unix}
|
|
\modulesynopsis{The most common \POSIX{} system calls (normally used
|
|
via module \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).
|
|
|
|
\strong{Do not import this module directly.} Instead, import the
|
|
module \refmodule{os}, which provides a \emph{portable} version of this
|
|
interface. On \UNIX{}, the \refmodule{os} module provides a superset of
|
|
the \module{posix} interface. On non-\UNIX{} operating systems the
|
|
\module{posix} module is not available, but a subset is always
|
|
available through the \refmodule{os} interface. Once \refmodule{os} is
|
|
imported, there is \emph{no} performance penalty in using it instead
|
|
of \module{posix}. In addition, \refmodule{os}\refstmodindex{os}
|
|
provides some additional functionality, such as automatically calling
|
|
\function{putenv()} when an entry in \code{os.environ} is changed.
|
|
|
|
The descriptions below are very terse; refer to the corresponding
|
|
\UNIX{} manual (or \POSIX{} documentation) entry for more information.
|
|
Arguments called \var{path} refer to a pathname given as a string.
|
|
|
|
Errors are reported as exceptions; the usual exceptions are given for
|
|
type errors, while errors reported by the system calls raise
|
|
\exception{error} (a synonym for the standard exception
|
|
\exception{OSError}), described below.
|
|
|
|
|
|
\subsection{Large File Support \label{posix-large-files}}
|
|
\sectionauthor{Steve Clift}{clift@mail.anacapa.net}
|
|
\index{large files}
|
|
\index{file!large files}
|
|
|
|
|
|
Several operating systems (including AIX, HPUX, Irix and Solaris)
|
|
provide support for files that are larger than 2 Gb from a C
|
|
programming model where \ctype{int} and \ctype{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
|
|
\ctype{off_t} is larger than a \ctype{long} and the \ctype{long long}
|
|
type is available and is at least as large as an \ctype{off_t}. Python
|
|
longs are then used to represent file sizes, offsets and other values
|
|
that can exceed the range of a Python int. 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:
|
|
|
|
\begin{verbatim}
|
|
CFLAGS="`getconf LFS_CFLAGS`" OPT="-g -O2 $CFLAGS" \
|
|
configure
|
|
\end{verbatim} % $ <-- bow to font-lock
|
|
|
|
|
|
\subsection{Module Contents \label{posix-contents}}
|
|
|
|
|
|
Module \module{posix} defines the following data item:
|
|
|
|
\begin{datadesc}{environ}
|
|
A dictionary representing the string environment at the time the
|
|
interpreter was started. For example, \code{environ['HOME']} is the
|
|
pathname of your home directory, equivalent to
|
|
\code{getenv("HOME")} in C.
|
|
|
|
Modifying this dictionary does not affect the string environment
|
|
passed on by \function{execv()}, \function{popen()} or
|
|
\function{system()}; if you need to change the environment, pass
|
|
\code{environ} to \function{execve()} or add variable assignments and
|
|
export statements to the command string for \function{system()} or
|
|
\function{popen()}.
|
|
|
|
\strong{Note:} The \refmodule{os} module provides an alternate
|
|
implementation of \code{environ} which updates the environment on
|
|
modification. Note also that updating \code{os.environ} will render
|
|
this dictionary obsolete. Use of the \refmodule{os} for this is
|
|
recommended over direct access to the \module{posix} module.
|
|
\end{datadesc}
|
|
|
|
Additional contents of this module should only be accessed via the
|
|
\refmodule{os} module; refer to the documentation for that module for
|
|
further information.
|