Difference among various logging methods

[E-Neutrino]

Am 22.07.14 22:37, schrieb Sabniveesu Shashank:
> [Avoiding application specific details for brevity; Please ask if needed]
> 
> Hi!
> 
> I could log data from an NS3 script into terminal. To save it, I did
> 
> ./waf --run=first|tee first.txt   (I see output on terminal; just an
> empty file is created)
> 
> ./waf --run=first > first.txt     (I see output on terminal; just an
> empty file is created)
> 
> ./waf --run=first >& first.txt    (saved 327 MB)
> 
> I found the last one in a blog. I don't understand why it alone is working.
> 
> Can someone respond?

 I don't know waf, but it looks like it outputs to stderr instead of
 stdout.  So the correct method would be

    ./waf --run=first 2> first.txt

 or (if you want to use tee)

    ./waf --run=first 2>&1 | tee first.txt

 the second form captures both stderr and stdout in first.txt

 An alternative way (without parallel terminal output) would be

    ./waf --run=first > first.txt 2>&1

 note the order of redirections: first you connect "first.txt" to the
 stdout channel, then you connect the stdout channel into the stderr
 channel.  The other order would not work.


 Hope this helps

    Neutrino

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