posix
— 最常见的 POSIX 系统调用
¶
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
, which provides a
portable
version of this interface. On Unix, the
os
module provides a superset of the
posix
interface. On non-Unix operating systems the
posix
module is not available, but a subset is always available through the
os
interface. Once
os
is imported, there is
no
performance penalty in using it instead of
posix
. In addition,
os
provides some additional functionality, such as automatically calling
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
.
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
和
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
In addition to many functions described in the
os
module documentation,
posix
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()
,
popen()
or
system()
; if you need to change the environment, pass
environ
to
execve()
or add variable assignments and export statements to the command string for
system()
or
popen()
.
3.2 版改变： 在 Unix，键和值是 bytes。
注意
os
module provides an alternate implementation of
environ
which updates the environment on modification. Note also that updating
os.environ
will render this dictionary obsolete. Use of the
os
module version of this is recommended over direct access to the
posix
模块。