Hello,
what is the better and correct way to perform a comparison:
I have been using the following with no problems:

if [[ $a = "" ]]
then ....
fi

I have seen this also used :
if [ $b -eq 1 ]
then ....
fi

When I try :
if [ $a = "" ]
then ....
fi

I get an error like .... the test condition expects a parameter.
Can anybody explain? Is it due to the data types and different type allow different comparison constructs?

Thanks!