bash function input $1 is only processing first word of string & formatting issue

Question

My BASH function:

json_format () {
        echo '{
                "question": "';echo "$1";echo '",' 
}

for:

json_format ${questions[$Q_counter]}

Is returning:

{
                "question": "
VM
",

Instead of expected json format and string:

{
    "question": "VM CPU is at 100% and you'r jumpbox creds be broken! What do you do?",

The string appears to be cut off at the space after the first word "VM", and the formatting is a little off with those echo commands. How can i correct my function? Thanks!

Answer 1

The ideal way to generate JSON from shell is to use a tool such as jq that actually understands the format:

json_format() {
  jq -n --arg q "$1" '{"question": $q}'
}

...or, if you have a Python interpreter, the built-in json module can also be used:

json_format() {
  python -c 'import sys, json; print json.dumps({"question": sys.argv[1]})' "$1"
}

If you don't have any of those tools, however, at least make a best-effort attempt at escaping:

json_format() {
  local s=$1
  s=${s//'\'/'\\'}   # replace \ with \\
  s=${s//'"'/'\"'}   # replace " with \"
  s=${s//$'\n'/'\n'} # replace newline literals with \n
  printf '{\n\t"question": "%s"\n}\n' "$s"
}

...or, to process one value at a time:

json_format() {
  local s=$1
  s=${s//'\'/'\\'}   # replace \ with \\
  s=${s//'"'/'\"'}   # replace " with \"
  s=${s//$'\n'/'\n'} # replace newline literals with \n
  printf '%s\n' "$s"
}

...invoked individually for each string to be formatted, as in:

cat <<EOF
{
  "question": "$(json_format "$question")",
  "image": "$(json_format "$image_url")",
  "choices": [ ],
  "correct": [ "$(json_format "$answer")" ],
  "explanation": "$(json_format "$explanation")"
}
EOF

---

This will work correctly with cases for which naive approaches will produce valid that is not in fact valid JSON. Consider, for instance:

# naive string substitution will fail here because it won't escape double quotes
json_format 'How do you spell "hello" in Spanish?'

or

# naive string substitution will fail here because it won't escape the newline
json_format $'This question has\ntwo lines'

or

# naive string substitution will fail here because it won't escape the backslash
json_format 'This question ends in a backslash: \'

Note, in all of the above, the quoting -- which ensures that the string is passed as a single argument.