os.pipe learning tips

os.pipe() 典型用法：

#!/usr/bin/python

import os, sys

print "The child will write text to a pipe and "
print "the parent will read the text written by child..."

# file descriptors r, w for reading and writing
r, w = os.pipe() 

processid = os.fork()
if processid:
    # This is the parent process 
    # Closes file descriptor w
    os.close(w)
    r = os.fdopen(r)
    print "Parent reading"
    str = r.read()
    print "text =", str
    os.waitpid(processid, 0) # wait for child process terminate
    sys.exit(0)
else:
    # This is the child process
    os.close(r)
    w = os.fdopen(w, ‘w‘)
    print "Child writing"
    w.write("Text written by child...")
    w.close()
    print "Child closing"
    sys.exit(0)

os.pipe() 的代码实现：

Tracing into module of os (os.py), and find there nothing about function of pipe(), except the following code clips:

_names = sys.builtin_module_names # names of built-in modules, with Windows OS, there will be an item of ‘nt‘ within this tuple, while on Posix (Unix, linux), there will be an item of ‘posix‘ 

# Note:  more names are added to __all__ later.
__all__ = ["altsep", "curdir", "pardir", "sep", "extsep", "pathsep", "linesep",
           "defpath", "name", "path", "devnull",
           "SEEK_SET", "SEEK_CUR", "SEEK_END"]

def _get_exports_list(module): # this function will get all the attributes which not starts with "_"
    try:
        return list(module.__all__)
    except AttributeError:
        return [n for n in dir(module) if n[0] != ‘_‘]

if ‘posix‘ in _names:
    name = ‘posix‘
    linesep = ‘\n‘
    from posix import * # import all the attributes of posix, within which pipe() is implemented as well as other posix system calls
    try:
        from posix import _exit
    except ImportError:
        pass
    import posixpath as path # that‘s where os.path come from

    import posix
    __all__.extend(_get_exports_list(posix)) # add all the attributes of posix to var __all__
    del posix

os.pipe() 的其他用法：

Another scenario of using os.pipe() is subprocess. The following source code comes from subprocess.py

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os.pipe learning tips

原文：http://blog.csdn.net/ispcfs/article/details/21468951