Say you have a list of files on your harddrive and you want to replace

/api/hello.json

with

/api/v2/hello.json

This can be done very easily with sed:

for f in ./swagger/v2/api/v2/*.json; do
echo $f
sed -i -e s/api\\//api\\/v2\\// $f
done

This command will overwrite your files and replace that URL.