Difference between revisions of "Jq"

Revision as of 01:14, 29 April 2016

jq is a lightweight and flexible command-line JSON processor. jq is like sed for JSON data - you can use it to slice and filter and map and transform structured data with the same ease that sed, awk, grep, and friends let you play with text.

Example usage

$ cat azones.json

{
    "availabilityZoneInfo": [
        {
            "hosts": {
                "node-1.example.com": {
                    "nova-compute": {
                        "active": true,
                        "available": true
                    }
                },
                "node-2.example.com": {
                    "nova-compute": {
                        "active": true,
                        "available": true
                    }
                }
            },
            "zoneName": "az1",
            "zoneState": {
                "available": true
            }
        },
        {
            "hosts": {
                "node-3.example.com": {
                    "nova-compute": {
                        "active": true,
                        "available": true
                    }
                },
                "node-4.example.com": {
                    "nova-compute": {
                        "active": true,
                        "available": true
                    }
                }
            },
            "zoneName": "az2",
            "zoneState": {
                "available": true
            }
        }
    ]
}

• Capture just the availability zone names:

$ cat azones.json | jq '[.availabilityZoneInfo[] | .zoneName]'

[
  "az1",
  "az2"
]

Or, for compact instead of pretty-printed output:

$ cat azones3.json | jq -c '[.availabilityZoneInfo[] | .zoneName]'
["az1","az2"]

• Capture just the hostname (e.g., "node-1.example.com") key for availability zone "az1":

$ cat azones.json | jq '[.availabilityZoneInfo[] | select(.zoneName == "az1") | {hosts: .hosts|keys}]'

[
  {
    "hosts": [
      "node-1.example.com",
      "node-2.example.com"
    ]
  }
]

Or, for a more script-friendly output:

$ cat azones.json | jq -cM '[.availabilityZoneInfo[] | select(.zoneName == "az1") | {hosts: .hosts|keys}]' | sed -e 's/["}\[]//g;s/\]//g;s/{hosts://g;s/,/ /g'
#~OR~
$ foo=($(cat azones3.json | jq -cM '[.availabilityZoneInfo[] | select(.zoneName == "az1") | {hosts: .hosts|keys}]' | sed -e 's/["}\[]//g;s/\]//g;s/{hosts://g;s/,/ /g'))
$ echo ${foo[0]} #=> node-1.example.com

• Get just the raw values:

$ echo '{ "packet_loss": [ {"ips": "10.0.0.10 10.0.0.11 10.0.0.12", "node-17": "3/3" }] }' | jq -r '[.packet_loss[] | .ips] | .[]'
10.0.0.10 10.0.0.11 10.0.0.12

Practical example

Here is how to print out all the OpenStack compute nodes in my example environment:

#!/bin/bash
# AUTHOR: Christoph Champ <christoph.champ@gmail.com>
# Requires jq 1.5+
JQ=$(which jq)

OS_AUTH_URL=http://1.2.3.4:5000/v2.0/
OS_TENANT_NAME=admin
OS_USERNAME=admin
OS_PASSWORD=admin

INFO=$(curl -sXPOST "${OS_AUTH_URL}/tokens" \
        -H "Content-Type: application/json" \
        -d "{\"auth\":{\"tenantName\":\"$OS_TENANT_NAME\",\"passwordCredentials\":\
        {\"username\":\"$OS_USERNAME\",\"password\":\"$OS_PASSWORD\"}}}" | \
        ${JQ} -crM '[.access.token.id + "," + (.access.serviceCatalog[] | select(.name == "nova") | .endpoints[].publicURL)] | .[]')

TOKEN=${INFO%%,*}
NOVA_ENDPOINT=${INFO#*,}

IGNORE_ZONES="internal|nova"

raw=$(curl -s -H "X-Auth-Token: ${TOKEN}" "${NOVA_ENDPOINT}/os-availability-zone/detail" | \
    ${JQ} -crM '[.availabilityZoneInfo[].zoneName] | .[]' | \
    grep -vE "(${IGNORE_ZONES})" | tr '\n' ',')

IFS=',' read -r -a zones <<< "${raw%,}"

for zone in "${zones[@]}"; do
    raw=($(curl -s -H "X-Auth-Token: ${TOKEN}" "${NOVA_ENDPOINT}/os-availability-zone/detail" | \
        ${JQ} --arg zone "$zone" '[.availabilityZoneInfo[] | select(.zoneName==$zone) | .hosts|keys] | .[]' | \
        tr -d '[]",' | sed '/^$/d' | tr '\n' ',' | tr -d ' '))

    IFS=',' read -r -a nodes <<< "${raw%,}"
    for node in "${nodes[@]}"; do
        echo "node: $zone $node"
    done
done

Running the above script produces the following output:

node: az1 node-1.example.com
node: az1 node-2.example.com
node: az2 node-3.example.com
node: az2 node-4.example.com

External links

• Official website