replacing double quotes with backslash and double quotes [duplicate]

Question

I am trying to replace a double quotes (") with back slash and double quotes (") however it's not working

echo '"hello workd"' | tr '"' '\\""'

This gives me

\hello workd\

and following does nothing.

echo '"hello workd"' | tr '"' '\"'

Answer 1

tr is not the right tool for this as it replaces one character with another. You may use sed like this:

echo '"hello workd"' | sed -E 's/"/\\&/g'

\"hello workd\"

In s/"/\\&/g we are matching a " and replacing with a \ followed by the full match i.e. " itself.