linux.softwareshinobi.com/landing/docs/Bash-Scripts/018-working-with-json-in-bash-using-jq.md

Json Data

jq is your lightweight, flexible command-line JSON processor. It's built in portable C with zero runtime dependencies, making it simple to install and powerful for parsing JSON in Bash.

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Demo Setup: QuizAPI

This demo uses the QuizAPI to fetch JSON data. Obtain a free API key from their client area to follow along.

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Installing jq

jq is easily installed via your system's package manager or direct download.

• Ubuntu/Debian: sudo apt-get install jq
• Red Hat/Fedora: sudo dnf install jq
• Arch Linux: sudo pacman -S jq

For other systems, refer to the official jq download page. Verify your installation:

jq --version

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Basic JSON Parsing with jq

Once jq is installed and you have your QuizAPI key, you can start processing JSON.

First, set your API key:

API_KEY=YOUR_API_KEY_HERE # Replace with your actual key

Fetch questions using curl:

curl "https://quizapi.io/api/v1/questions?apiKey=${API_KEY}&limit=10"

The raw output is hard to read. Pipe it to jq for beautifully formatted and colored JSON:

curl "https://quizapi.io/api/v1/questions?apiKey=${API_KEY}&limit=10" | jq

This command makes the JSON output structured and easy to inspect.

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Extracting Specific Elements

To get only the first element from a JSON array, use .[0]:

curl "https://quizapi.io/api/v1/questions?apiKey=${API_KEY}&limit=10" | jq '.[0]'

This will output only the first JSON object in the array.

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Fetching Key Values Across an Array

To extract the value of a specific key (e.g., question) from every object in a JSON array, use .[].key:

curl "https://quizapi.io/api/v1/questions?apiKey=${API_KEY}&limit=10" | jq '.[].question'

This will return a list of all questions from the API response.

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Integrating jq into a Bash Script

Let's create a script to fetch a question and its answers, then display them. We'll use jq to parse specific fields and assign them to Bash variables.

Create quiz_script.sh:

touch quiz_script.sh

Open quiz_script.sh and add (remember to replace YOUR_API_KEY_HERE):

#!/usr/bin/env bash

# Your QuizAPI Key (replace YOUR_API_KEY_HERE with your actual key)
API_KEY="YOUR_API_KEY_HERE"

# Make an API call and get the first question object
# Using -s for silent mode to suppress curl's progress meter
QUIZ_DATA=$(curl -s "https://quizapi.io/api/v1/questions?apiKey=${API_KEY}&limit=1" 2>/dev/null)

# Extract specific values using jq with raw output (-r) for Bash variables
question=$(echo "${QUIZ_DATA}" | jq -r '.[0].question')
answer_a=$(echo "${QUIZ_DATA}" | jq -r '.[0].answers.answer_a')
answer_b=$(echo "${QUIZ_DATA}" | jq -r '.[0].answers.answer_b')
answer_c=$(echo "${QUIZ_DATA}" | jq -r '.[0].answers.answer_c')
answer_d=$(echo "${QUIZ_DATA}" | jq -r '.[0].answers.answer_d')

# Output the question and answers
echo "
Question: ${question}

A) ${answer_a}
B) ${answer_b}
C) ${answer_c}
D) ${answer_d}
"

Save, make executable, and run:

chmod +x quiz_script.sh
./quiz_script.sh

The script will print a random question and its corresponding answers. For more advanced, interactive Bash quizzes, explore community projects that build upon these jq principles.

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Conclusion

jq empowers you to process JSON directly within your Bash terminal, facilitating seamless interaction with REST APIs. For deeper dives, consult the official jq manual and the QuizAPI documentation.

{notice} This content was inspired by a piece by softwareshinobi on Dev Team Six.