BASH/SED: Match a line, then repeat that line n times immediately after match

Let’s say I have a file called template.inp containing the following:

filename
clustername
>>>>
repeatline 0. 0. 0. z. z. z.
>>>>
do_something.sh
>>>>

And I want to match on repeatline and then copy that whole line $repeatnum times, such that template.inp looks like for repeatnum=2:

filename
clustername
>>>>
repeatline 0. 0. 0. z. z. z.
repeatline 0. 0. 0. z. z. z.
repeatline 0. 0. 0. z. z. z.
>>>>
do_something.sh
>>>>

Not sure how to do this elegantly.

>Solution :

I don’t think it’s easy to do repeat a line a variable number of times in sed. But you can do it with a simple shell loop.

while read -r line; do
    echo "$line"
    if [[ "$line" == repeatline* ]]
        for ((i=0; i<repeatnum; i++)) do
            echo "$line"
        done ;;
    fi
done < template.inp > template.outp
mv template.outp template.inp