Question

I want to use sed to replace all ' with \' and all " with \". Example input:

"a" 'b'

Output:

\"a\" \'b\'

Answer 1

There’s no ? character in your post, but I’ll assume your question is “How do I do such a replacement?”. I just made a quick test file with your input, and this command line seems to work:

sed -e 's#"#\\"#g' -e "s#'#\\\'#g"

Example:

$ cat input 
"a" 'b'
$ sed -e 's#"#\\"#g' -e "s#'#\\\'#g" input 
\"a\" \'b\'