How do I escape quotes for JSON conversion in Bash

I have a file which I need to convert to a JSON string and it needs to be done via bash. My test file looks like 1 2 ' 3 4 Here is what's happening $ LOG=$(cat file) $ printf '{"log": "%q"}\n' "$LOG" {"log": "$'1\n2\n\'\n3\n4'"} Things seem ok like it's handling the newlines and the ', but it's adding a $' at the start and a ' at the end.