Escaping characters in bash (for JSON)

Escaping characters in bash for JSON can be done using various methods.

Using sed:

MSG=$(echo $MSG | sed "s/'/\\\\\'/g")

Using Bash's string manipulation features:

MSG=${MSG//\'/\\\'}

These methods replace single quotes (') with escaped versions (\').

Using jq:

MSG=$(jq -Rsa <<< "$MSG")

This converts a string to a valid JSON string, handling escaping of special characters and Unicode characters.

Using Perl:

json_escape () {
    printf '%s' "$1" | perl -pe 's/(\\(\\\\)*)/$1$1/g; s/(?!\\)(["\x00-\x1f])/sprintf("\\u%04x",ord($1))/eg;'
}

This is a non-invasive solution that handles unicode.

Using xidel:

$ git log -n 1 --pretty=format:'%s' | xidel -se 'serialize({"text":$raw},{"method":"json","encoding":"us-ascii"})' --output-format=bash

This creates a properly escaped JSON object using the serialize function.

Using a JSON-aware tool:

Using a tool like json_stringify or jq can simplify the escaping process.

Using Node.js:

MSG=$(MSG=$MSG node -p "JSON.stringify(process.env.MSG)")

This uses Node.js's JSON.stringify() function to escape the string.

Using a custom escape function:

function escape_json_string() {
  local input=$1
  for ((i = 0; i < ${#input}; i++)); do
    local char="${input:i:1}"
    local escaped="${char}"
    case "${char}" in
        $'"' ) escaped="\\\""
        $'\\') escaped="\\\\"
        $'/' ) escaped="\\/"
        $'\b') escaped="\\b"
        $'\f') escaped="\\f"
        $'\n') escaped="\\n"
        $'\r') escaped="\\r"
        $'\t') escaped="\\t"
        *) 
          if [[ "${char}" < $'\x20' ]]; then
            escaped=$(printf "\u%04X" "'${char}")
          fi
          ;;
    esac
    echo -n "${escaped}"
  done
}

This iterates over characters and escapes them as per the JSON specification.