Le 03/12/2010 14:46, Payam Poursaied a écrit :
>
> Hi all,
> I'm not sure this is a bug or please let me know the concept:
> What is the difference between:
> ls -R /etc/ 2>&1 1>/dev/null
> and
> ls -R /etc/ 1>/dev/null 2>&1
>
> the second one redirect everything to /dev/null but the first one, still
> prints errors (run as a non root user would unveil the problem)
> it the order of arguments important? If yes, what is the idea/concept behind
> this behavior?
I was confused by this for a long time and kept reading again and
again the correct but *too long* answers others have posted, until I
started using this *short* reading trick:
2>&1 1>/dev/null
output2 := output1; output1 := NULL
When you apply this from left to right it should be quite obvious
why output2 is not NULL.
And now you can finally understand things like this:
exec 3>&1 4>&2 # save
exec 1>/dev/null 2>&1
# .... discard everything ...
exec 1>&3 2>&4 # restore
