[Tutor] [unclassified] Re: Pipe variable to external command (fwd)

[Jeffrey Rice]

At 12:24 PM 5/12/2005, Danny Yoo wrote:
>######
> >>> import popen2
> >>> process = popen2.Popen3(['wc'])
> >>> process.tochild.write("hello\nworld")
> >>> process.tochild.close()
> >>> process.fromchild.read()
>'      1       2      11\n'
> >>> process.fromchild.close()
> >>> process.wait()
>0
>######

This is all well and good if the child exits with 0, but things get a 
little funky if it doesn't.

For example, modifying the model to have clamdscan exit with 0:

######
 >>> import popen2
 >>> process = popen2.Popen3(['clamdscan','ham.test'])
 >>> process.tochild.close()
 >>> process.fromchild.read()
'ham.test: OK\n\n----------- SCAN SUMMARY -----------\nInfected files: 
0\nTime: 0.098 sec (0 m 0 s)\n'
 >>> process.fromchild.close()
 >>> process.wait()
0
######

Now rewrite it to return an exit code of 1:

######
 >>> import popen2
 >>> process = popen2.Popen3(['clamdscan','eicar.test'])
 >>> process.tochild.write("hello\nworld")
 >>> process.tochild.close()
 >>> process.fromchild.read()
'eicar.test: Eicar-Test-Signature FOUND\n\n----------- SCAN SUMMARY 
-----------\nInfected files: 1\nTime: 0.043 sec (0 m 0 s)\n'
 >>> process.fromchild.close()
 >>> process.wait()
256
######

Now for a exit code of 2:

######
 >>> import popen2
 >>> process = popen2.Popen3(['clamdscan','nonexistent.test'])
 >>> process.tochild.close()
 >>> process.fromchild.read()
'\n----------- SCAN SUMMARY -----------\nInfected files: 0\nTime: 0.004 sec 
(0 m 0 s)\n'
 >>> process.fromchild.close()
 >>> process.wait()
512
######

In my fiirst example, clamdscan should return 1 when the EICAR string is 
found -- process.wait() gets 256 instead.
In the second, clamdscan returns 2 if an error occurs, such as trying to 
scan a non-existent file, but 512 is returned.

No doubt there is a reason why the exit code is getting multiplied by 
256... ???  My search has not enlightened me, however.

Jeff


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Jeffrey Rice    ||     jeffrice at finity.org      ||  www.finity.org