On Dec 9, 2008, at 2:26 PM, Lars Kotthoff wrote:
Dear list,
I recently noticed a python program which uses forks and pipes for
communication between the processes not behaving as expected. The
minimal
example program:
[snip]
This prints out "foo" twice although it's only written once to the
pipe. It
seems that python doesn't flush file descriptors before copying them
to the
child process, thus resulting in the duplicate message. The
equivalent C
program behaves as expected,
[snip]
Is this behaviour intentional? I've tested both python and C on
Linux, OpenBSD
and Solaris (python versions 2.5.2 and 2.3.3), the behaviour was the
same
everywhere.
Yes, it's intentional. And, no, your programs aren't equivalent.
Rewrite your C program to use fdopen, and fread/fwrite. *Then* it will
be equivalent and have the same behavior as the python program.
Alternatively, you can change your python program to use os.read/
os.write instead of fdopen and fileobject.read/fileobject.write, if
you want your python program to work like the C program.
James
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