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.