After replacing " \n" with "\n", although the white space is removed, all 
the lines with "\n" becomes ^@

I wonder whether this is due to the file originally in Excel (export to 
text). But dos2unix does not solve... 

Ela wrote:
> After replacing " \n" with "\n", although the white space is removed, all 
> the lines with "\n" becomes ^@
> 
> I wonder whether this is due to the file originally in Excel (export to 
> text). But dos2unix does not solve... 
> 
> 

You could use od or favorite hex/octal viewing program to see
what characters are actually there in the original.

What command did you use to make the replace?