How to format a bash array as a JSON array

Question

I have a bash array

X=(\"hello world\" \"goodnight moon\")

That I want to turn into a json array

[\"hello world\", \"goodni         


        

Answer 1

You can do this:

X=("hello world" "goodnight moon")
printf '%s\n' "${X[@]}" | jq -R . | jq -s .

output

[
  "hello world",
  "goodnight moon"
]

Answer 2

If you're OK with a few extra backslashes, bash's printf "%q" is useful:

X=("hello world" "goodnight moon" 'say "boo"' 'foo\bar')
json="[$(printf '"%q",' "${X[@]}")"
json="${json%,}]"
echo "$json"

["hello\ world","goodnight\ moon","say\ \"boo\"","foo\\bar"]

---

Regarding the OK-ness of the backslashes: node.js doesn't have a problem with them:

$ node
> x = ["hello\ world","goodnight\ moon","say\ \"boo\"","foo\\bar"]
[ 'hello world',
  'goodnight moon',
  'say "boo"',
  'foo\\bar' ]

Answer 3

This ...

X=("hello world" "goodnight moon" 'say "boo"' 'foo\bar')

json_array() {
  echo -n '['
  while [ $# -gt 0 ]; do
    x=${1//\\/\\\\}
    echo -n \"${x//\"/\\\"}\"
    [ $# -gt 1 ] && echo -n ', '
    shift
  done
  echo ']'
}

json_array "${X[@]}"

... yields:

["hello world", "goodnight moon", "say \"boo\"", "foo\\bar"]

If you are planning to do a lot of this (as your reluctance to use a subshell suggests) then something such as this that does not rely on any subprocess is likely to your advantage.

Answer 4

You can use:

X=("hello world" "goodnight moon")
sed 's/^/[/; s/,$/]/' <(printf '"%s",' "${X[@]}") | jq -s '.'
[
  [
    "hello world",
    "goodnight moon"
  ]
]

Answer 5

If the values do not contain ASCII control characters, which have to be escaped in strings in valid JSON, you can also use sed:

$ X=("hello world" "goodnight moon")
$ printf %s\\n "${X[@]}"|sed 's/["\]/\\&/g;s/.*/"&"/;1s/^/[/;$s/$/]/;$!s/$/,/'
["hello world",
"goodnight moon"]

If the values contain ASCII control characters, you can do something like this:

X=($'a\ta' $'a\n\\\"')
for((i=0;i<${#X[@]};i++));do
  [ $i = 0 ]&&printf \[
  printf \"
  e=${X[i]}
  e=${e//\\/\\\\}
  e=${e//\"/\\\"}
  for((j=0;j<${#e};j++));do
    c=${e:j:1}
    if [[ $c = [[:cntrl:]] ]];then
      printf '\\u%04x' "'$c"
    else
      printf %s "$c"
    fi
  done
  printf \"
  if((i<=${#X[@]}-2));then
    printf ,
  else
    printf \]
  fi
done