Substitua o texto por sed
sed -i 's/old-text/new-text/g' input.txt
Clear Caterpillar
sed -i 's/old-text/new-text/g' input.txt
sed -i 's/foo/bar/g' hello.txt
Just concatenate var '"$var"' to replace values string in sed command:
$ sed -i 's/string_to_replace/'"$var"'/g' file_to_replace.txt
#on my mac
sed -i -e 's/old-text/new-text/g' text.txt