sylye sylye - 1 month ago 19
JSON Question

Loop through json using jq to get multiple value

Here is volumes.json :

{
"Volumes": [
{
"AvailabilityZone": "us-east-1a",
"Tags": [
{
"Value": "vol-rescue-system",
"Key": "Name"
}
],
"VolumeId": "vol-00112233",
},
{
"AvailabilityZone": "us-east-1a",
"Tags": [
{
"Value": "vol-rescue-swap",
"Key": "Name"
}
],
"VolumeId": "vol-00112234",
},
{
"AvailabilityZone": "us-east-1a",
"Tags": [
{
"Value": "vol-rescue-storage",
"Key": "Name"
}
],
"VolumeId": "vol-00112235",
}
]
}


I need to get both the value of
VolumeId
and
Tags.Value
to be used as the input to invoke another command. It is easy to get a single value from the json array, but I am not able to extract multiple value from it and pass it to another bash command.

I can get a single value using this:

cat volumes.json |jq -r '.Volumes[].VolumeId' |while read v; do another_bash_command $v; done


but I am not able to get multiple value cause this is wrong:

cat volumes.json |jq -r '.Volumes[].VolumeId, .Volumes[].Tags[].Value' |while read v w; do another_bash_command $v $w; done


as it will then loop 6 times of the outcome instead of 3.

And, how do I pass those multiple json value in the loop to a bash array so I can use the value in a better way ? Like
VolumeId-> $arr[0][0]
,
Tags.Value-> $arr[0][1]
,
AvailabilityZone-> $arr[0][2]
...etc. I have searched through SO and the jq docs, and tried
readarray
, but still not able to find out the solution :( Thanks for any help given.

Answer

It seems to me that you want to output the two values (VolumeId and Tags[].Value) on the same line?

If that's the case, then a simple string concatenation should be enough:

$ jq -r '.Volumes[] | .VolumeId + " " + .Tags[].Value' volumes.json
vol-00112233 vol-rescue-system
vol-00112234 vol-rescue-swap
vol-00112235 vol-rescue-storage

The above can then be used in a pipeline with while-read:

$ cat my_script
jq -r '.Volumes[] | .VolumeId + " " + .Tags[].Value' volumes.json \
| while IFS= read -r volumeId tagValue; do
  other_command "$volumeId" "$tagValue"
done

You should note that if there is more than one element in Tags the result will reflect that. This can however be avoided by referring the first element in Tags: .Tags[0].Value

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