excuse me if i did not clearly stated the prob. Consider this piece of code:

if( $3 == "R001" )
print "xxx";
else
print "yyy";
fi

my question is why can't I use the following instead of above:

if [[ $3 = "R001" ]]
print "xxx"
else
print "yyy"
fi

Also, is there is a difference in () and [[ ]] in above two examples?

Thanks