CODEWITHSUNDEEP
jsonbashparameter-passingjq
lisi4ok
lisi4ok

Reputation: 785

passing arguments to jq filter

Here is my config.json:

{
    "env": "dev",
    "dev": {
        "projects" : {
            "prj1": {
                "dependencies": {},
                "description": ""
            }
        }
    }
}

Here are my bash commands:

PRJNAME='prj1'

echo $PRJNAME

jq --arg v "$PRJNAME" '.dev.projects."$v"' config.json 
jq '.dev.projects.prj1' config.json

The output:

prj1
null
{
  "dependencies": {},
  "description": ""
}

So $PRJNAME is prj1, but the first invocation only outputs null.

Can someone help me?

Upvotes: 71

Views: 163392

Answers (5)

Jebediah Khalil
Jebediah Khalil

Reputation: 11

My example bash command to replace an array in a json file. Everything is in variables:

a=/opt/terminal/conf/config.json ; \
b='["alchohol"]' ; \
c=terminal.canceledInspections.resultSendReasons ; \
cat $a | jq .$c ; \
cat $a | jq --argjson b $b --arg c $c 'getpath($c / ".") = $b' | sponge $a ; \
cat $a | jq .$c

Upvotes: 1

Z.San
Z.San

Reputation: 51

you can do this:


    key="dev.projects.prj1"
    filter=".$key"
    cat config.json | jq $filter

Upvotes: 5

Sebastien DIAZ
Sebastien DIAZ

Reputation: 431

You can use --argjson too when you make your json.

--arg a v       # set variable $a to value <v>;
--argjson a v   # set variable $a to JSON value <v>;

Upvotes: 42

LuWa
LuWa

Reputation: 361

As asked in a comment above there's a way to pass multiple argumets. Maybe there's a more elegant way, but it works.

  • If you are sure always all keys needed you can use this:
jq --arg key1 $k1 --arg key2 $k2 --arg key3 $k3 --arg key4 $k4 '.[$key1] | .[$key2] | .[$key3] | .[$key4] '
  • If the key isn't always used you could do it like this:
jq --arg key $k ' if key != "" then .[$key] else . end'
  • If key sometimes refers to an array:
jq --arg key $k ' if type == "array" then .[$key |tonumber] else .[$key] end'

of course you can combine these!

Upvotes: 25

user3899165
user3899165

Reputation:

The jq program .dev.projects."$v" in your example will literally try to find a key named "$v". Try the following instead:

jq --arg v "$PRJNAME" '.dev.projects[$v]' config.json

Upvotes: 109

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