Add new element to existing JSON array with jq in a shell script: problem with variable expansion

Question

as described in "Add new element to existing JSON array with jq" I am using this jq form to add elements to a JSON array.

This works fine in the command line. Short minimal version here:

jq '."schemes" += [{ JSON STRING HERE }]' settings.json > settings.json.new

Long, complete version here, I am trying to add a colorscheme to the windows terminal app:

jq '."schemes" += [{
  "name": "Grape",
  "black": "#2d283f",
  "red": "#ed2261",
  "green": "#1fa91b",
  "yellow": "#8ddc20",
  "blue": "#487df4",
  "purple": "#8d35c9",
  "cyan": "#3bdeed",
  "white": "#9e9ea0",
  "brightBlack": "#59516a",
  "brightRed": "#f0729a",
  "brightGreen": "#53aa5e",
  "brightYellow": "#b2dc87",
  "brightBlue": "#a9bcec",
  "brightPurple": "#ad81c2",
  "brightCyan": "#9de3eb",
  "brightWhite": "#a288f7",
  "background": "#171423",
  "foreground": "#9f9fa1",
  "selectionBackground": "#493d70",
  "cursorColor": "#a288f7"
}]' ./settings.json > ./settings.json.new

As said, this works great, and the new colorscheme shows up in Windows Terminal settings. However, when trying to automate this in a shell (bash) script, jq chokes.

# usage is add_colorscheme.sh colorscheme.json
colorscheme=$1
json_content=`cat ${colorscheme}`
json_file="settings.json"
jq '."schemes" += [${json_content}] ${json_file} > ${json_file}.new

I have tried many ways to expand variables, e.g. without braces ($json_content), and have also tried without success with other incantations. For example, using --argjson in the terminal:

json_content=`cat file.json`
echo ${json_content}
{ "name": "Grape", "black": "#2d283f", "red": "#ed2261", "green": "#1fa91b", "yellow": "#8ddc20", "blue": "#487df4", "purple": "#8d35c9", "cyan": "#3bdeed", "white": "#9e9ea0", "brightBlack": "#59516a", "brightRed": "#f0729a", "brightGreen": "#53aa5e", "brightYellow": "#b2dc87", "brightBlue": "#a9bcec", "brightPurple": "#ad81c2", "brightCyan": "#9de3eb", "brightWhite": "#a288f7", "background": "#171423", "foreground": "#9f9fa1", "selectionBackground": "#493d70", "cursorColor": "#a288f7" }
# but jq fails
jq --argjson content ${json_content} '."schemes" += [$content]'
jq: invalid JSON text passed to --argjson
Use jq --help for help with command-line options,
or see the jq manpage, or online docs  at https://jqlang.github.io/jq

or --arg

jq -n --arg content ${json_content} '."schemes" += [env.content]' settings.json
jq: error: syntax error, unexpected ':', expecting end of file (Unix shell quoting issues?) at <top-level>, line 1:
"name":
jq: 1 compile error

I have read a number of other posts like this one, on the topic of jq and variable expansions, but not sure how to even try here strings when I can't even get --arg nor --argjson to work.

I have tried exchanging -n --argjson to --argjson foo bar -n to no avail. I have even read the manpage! There's nothing special about --argjson there that I can see.

What am I doing wrong? Thanks for any help!

My system and context: Ubuntu 24.04.2 LTS, WSL2 jq: v1.7

colorscheme.json:

{
  "name": "Grape",
  "black": "#2d283f",
  "red": "#ed2261",
  "green": "#1fa91b",
  "yellow": "#8ddc20",
  "blue": "#487df4",
  "purple": "#8d35c9",
  "cyan": "#3bdeed",
  "white": "#9e9ea0",
  "brightBlack": "#59516a",
  "brightRed": "#f0729a",
  "brightGreen": "#53aa5e",
  "brightYellow": "#b2dc87",
  "brightBlue": "#a9bcec",
  "brightPurple": "#ad81c2",
  "brightCyan": "#9de3eb",
  "brightWhite": "#a288f7",
  "background": "#171423",
  "foreground": "#9f9fa1",
  "selectionBackground": "#493d70",
  "cursorColor": "#a288f7"
}

settings.json:

{
    "$help": "https://aka.ms/terminal-documentation",
    "$schema": "https://aka.ms/terminal-profiles-schema",
    "language": "en-US",
    "themes": [],
    "schemes": []
}

In bash, single quotes block variable expansion. You might need something like jq ".\"schemes\" += [${json_content}] ${json_file}" > ${json_file}.new to get your variables expanded in the jq query. — joanis
– joanis, Commented Jul 23 at 3:16
Great, thanks! that was it, got my brain exhausted it seems, all makes complete sense now. — fernan
– fernan, Commented Jul 23 at 19:14

oguz ismail · Accepted Answer · 2025-07-23 04:20:55Z

2

Try this instead:

jq '.schemes += [inputs]' "$json_file" "$@" >"$json_file.new"

answered Jul 23 at 4:20

oguz ismail

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3 Comments

fernan Jul 23 at 19:29

not sure if I understand your proposed solution correctly, I'm replacing $@ with the variable containing the JSON string, but it gives an error: jq '.schemes += [inputs]' "${settings_file}" "${json_content}" > "${settings_file}.new" jq: error: could not open file { "name": "colorschemeName", "black": "#2d283f", ... File name too long. Seems like this way of adding contents after the json file is being treated as a filename?

oguz ismail Jul 23 at 19:34

Leave it as is and it'll work. $@ is the list of arguments your script is called with.

fernan Jul 23 at 20:16

Oh! yes, it works, didn't know about $@ in bash. seems like in my case gives the same result as $1 because I'm only specifying one additional json file containing a single colorscheme to add. Works beautifully now, thanks!

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