Running bash commands for each JSON item through jq

Question

I would like to run a bash command for each field in a JSON formatted piece of data by leveraging jq.

{
    "apps": {
        "firefox": "1.0.0",
        "ie": "1.0.1",
        "chrome": "2.0.0"
    }
}

Basically I want something of the sort:

foreach app:
   echo "$key $val"
done

Solution 1

Assuming you wanted to list out the key/values of the apps object:

$ jq -r '.apps | to_entries[] | "\(.key)\t\(.value)"' input.json

To invoke another program using the output as arguments, you should get acquainted with xargs:

$ jq -r '...' input.json | xargs some_program

Solution 2

Here is an bash script which demonstrates a possible solution.

#!/bin/bash
json='
{
    "apps": {
        "firefox": "1.0.0",
        "ie": "1.0.1",
        "chrome": "2.0.0"
    }
}'

jq -M -r '
    .apps | keys[] as $k | $k, .[$k]
' <<< "$json" | \
while read -r key; read -r val; do
   echo "$key $val"
done

Example output

chrome 2.0.0
firefox 1.0.0
ie 1.0.1

Comments

[solemnify]

What if I wanted to actually run a tool against those values, ie: foreach app: mytool $key $val done

[s.meijer]

@JeffMercado a little more explanation to that comment would be most welcome. Let's say @solemnify is trying to run a command like apt-get install ${APP} -y. What whould the xargs format be?

[Jeff Mercado]

@s.meijer: I'd say check the manpages for it. But that one should be simple. You could do something like: jq '"filter to select package names"' input.json | xargs -i apt-get install {} -y

[Marcin]

Given the quoting/bracketing cruft in json this is unlikely to work as expected unless some_program takes only 1 argument.