add string in each line at the begining of column

Question

I digged many threads, but neither of them adresses this question as it stands.

I am interested in addind string chr to the begining of column in each line. File is tab delimited, looks sth like:

re1 1   AGT
re2 1   AGT
re3 2   ACGTCA
re12    3   ACGTACT

what I need is:

re1 chr1    AGT
re2 chr1    AGT
re3 chr2    ACGTCA
re12    chr3    ACGTACT

Can be in bash oneliner

many thanks for any help, cheers, Irek

Answer 1

What about this?

$ awk '$2="chr"$2' file
re1 chr1 AGT
re2 chr1 AGT
re3 chr2 ACGTCA
re12 chr3 ACGTACT

Explanation

With $2="chr"$2 we add chr to the 2nd field. Then we do not need any other command to get the desired output, as the default behaviour of awk is print $0.

To make sure the OFS (output field separator) is a tab, you can do the following:

$ awk 'BEGIN{OFS="\t"}$2="chr"$2' file
re1     chr1    AGT
re2     chr1    AGT
re3     chr2    ACGTCA
re12    chr3    ACGTACT

Answer 2

Awk one-liner do?

$ awk -v OFS=$'\t' '{ $2="chr" $2; print}' so.txt
re1     chr1    AGT
re2     chr1    AGT
re3     chr2    ACGTCA
re12    chr3    ACGTACT

Answer 3

sed one-liner:

sed 's/\<[0-9]\>/chr&/' < input > output