Hi Scrutinizer,
Thanks again.
It worked perfectly with my sample sequence provided.
However I aware if I replace it with my real own data set.
It just print out the original File 1
Would it the fasta sequence length issue?
My original file is around 2 million word and is single line.
My File 1 is 2 Line; First Line is header description and second line is a very long word (around 2 million).
My File 2 is tab-delimited file.
First column is the header of File 1;
Second column is the word to replace in File 1;
Third column is position of word to replace in File 1;