[python-win32] win32pipe and buffer size

[Frank Guenther]

Thanks for the reply, but it seems I run into the same problem like 
before when I use the subprocess module.

I modified your example in the following way:

---- echo.py
import sys

if __name__ == '__main__':
    while 1:
        indata = sys.stdin.readline()
        if indata=='end\n': break
        sys.stdout.write( 'echo>'+indata)
        sys.stdout.flush() #!!!!!!!!!!!! don't work without

---- caller.py
import subprocess

if __name__ == '__main__':
    child = subprocess.Popen(
        ['python', 'echo.py'],
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE
        )
   
    i=1
    while i<10:
        child.stdin.write('spam'+str(i)+'\n')
        data = child.stdout.readline()   
        print data
        i+=1
   
    child.stdin.write('end\n')

Now the problem arises if I comment line 8 "sys.stdout.flush()" or 
replace line 7 and 8 by "print 'echo>'+indata"
The tool I try to automate has the same behavior.
But there must be a way to get the text that is printed by the tool.
Is it necessary to use more low-level access and in which way, 
win32file, etc... ?

Tschau,
     Frank


kveretennicov at gmail.com wrote:

>On 7/11/05, Frank Guenther <xeoicq at netscape.net> wrote:
>  
>
>>Hi All,
>>
>>I try to automate a command line tool and have the problem that I can't
>>read the stdout-pipe.
>>I think the reason is the tool doesn't flush the pipe so  it is first
>>readable when the process was closed.
>>Can I set the buffer size of the stdout-pipe by win32pipe to force the
>>tool to write to the pipe?
>>
>>Is there a possibility to use win32file to get a low-level access to the
>>pipes or some other solution to the problem?
>>    
>>
>
>Have you tried standard subprocess module? It uses unbuffered i/o by default.
>
>  
>
>>I would be thankful for some hints and example code.
>>    
>>
>
>Hope this helps:
>
>---- echo.py
>
>import sys
>
>if __name__ == '__main__':
>    print 'echo>',
>    print sys.stdin.readline()
>
>---- caller.py
>
>import subprocess
>
>if __name__ == '__main__':
>    child = subprocess.Popen(
>        ['python', 'echo.py'],
>        stdin=subprocess.PIPE,
>        stdout=subprocess.PIPE
>        )
>    child.stdin.write('spam\n')
>    print 'received:', child.stdout.readline()
>    child.wait()
>
>- kv
>  
>
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