Pass an array variable to jq in bash

Question

Is it possible to pass and use in jq a variable of type array?

jq --arg ips "${IPs[0]}" '.nodes.app.ip = $ips[0] | .nodes.data.ip = $ips[1]' nodes.json

You're showing an array of exactly two items. Is that degenerate case really all you want? — Charles Duffy
– Charles Duffy, Commented Oct 15, 2019 at 17:25
Also, do you need only the easy case where no array element can contain a literal newline? — Charles Duffy
– Charles Duffy, Commented Oct 15, 2019 at 17:26

Charles Duffy · Accepted Answer · 2019-10-15 17:36:17Z

3

The general case solution is to pass that array in on stdin with NUL delimiters:

IPs=( 1.2.3.4 5.6.7.8 )
original_doc='{"nodes": { "app": {}, "data": {} }}'

jq -Rn --argjson original_doc "$original_doc" '
  input | split("\u0000") as $ips
  | $original_doc
  | .nodes.app.ip = $ips[0]
  | .nodes.data.ip = $ips[1]
' < <(printf '%s\0' "${IPs[@]}")

...emits as output:

{
  "nodes": {
    "app": {
      "ip": "1.2.3.4"
    },
    "data": {
      "ip": "5.6.7.8"
    }
  }
}

This is overkill for an array of IP addresses, but it works in the general case, even for actively-hostile arrays (ones with literal quotes, literal newlines, and other data that's intentionally hard-to-parse).

If you want to keep stdin clean, you can use a second copy of jq to convert your array to JSON:

IPs=( 1.2.3.4 5.6.7.8 )
IPs_json=$(jq -Rns 'input | split("\u0000")' < <(printf '%s\0' "${IPs[@]}"))

jq --argjson ips "$IPs_json" '
    .nodes.app.ip = $ips[0]
  | .nodes.data.ip = $ips[1]
' <<<'{"nodes": { "app": {}, "data": {} }}'

edited Oct 15, 2019 at 17:36

answered Oct 15, 2019 at 17:28

Charles Duffy

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1 Comment

ybonda Over a year ago

Its working locally, but when I'm sending it via ssh jq doesn't work properly... stackoverflow.com/questions/58428131/…

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