Write a bashscript to double every newline character in a text file?

Question

I need a bash script that will take a file and add a second \n character for every \n character already in the file:

that is:

abcd\nbcda

becomes

abcd\n\nbcda

how do I start. OR, should I write it in another language and wrap it in bash?

Answer 1

sed 'G' file > newfile

or

perl -nae 'print "$_\n";' file > newfile

or

while read ln
do
   echo $ln; echo;
done < file > newfile

Answer 2

A very very simple way to do it.

cat inputfile.txt | while read a
do
echo $a >> outputfile.txt
echo "" >> outputfile.txt
done

Answer 3

sed can do this quite easily

sed 'G' file