please elaborate on nmap stnderr and stndio

["Mike ." <dmciscobgp () hotmail com>]

hello


im not a code guru so im still green on some things. i mentioned before about the using >2 nul that someone brought to 
my attention to filter certain items out in a scan. i would like to know how we know what is considered an "error" in 
that particular file stream. example i am using is here. this shows up in a normal output using the following line :

 nmap -vv -n -T4 -Pn -dd 192.168.0.10 -p 1500


truncated part >

Nmap scan report for 192.168.0.10
Fetchfile found C:\Program Files\Nmap/nmap-mac-prefixes
MAC prefix 0001C8 is duplicated in C:\Program Files\Nmap/nmap-mac-prefixes; ignoring duplicates.
MAC prefix 080030 is duplicated in C:\Program Files\Nmap/nmap-mac-prefixes; ignoring duplicates.
MAC prefix 080030 is duplicated in C:\Program Files\Nmap/nmap-mac-prefixes; ignoring duplicates.

now if i use the >2 nul option to redirect file stream, i no longer see that portion in the debug output. why is this? 
the NSOCK info i can understand being filtered out, why the above? what constitutes an ERROR as far as nmap is 
concerned regarding output?

hope that makes sense and thanks
Mike

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