jello (with examples)

Pretty-print JSON or JSON-Lines data

Code:

cat file.json | jello

Motivation:

When dealing with large amounts of JSON or JSON-Lines data, it can be challenging to read and understand the structure. Pretty-printing the data makes it more readable and easier to navigate.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• No additional arguments are provided, so jello will pretty-print the JSON data from stdin to stdout.

Example Output:

{
    "key1": "value1",
    "key2": "value2"
}
{
    "key3": "value3",
    "key4": "value4"
}

Output a schema of JSON or JSON-Lines data

Code:

cat file.json | jello -s

Motivation:

Determining the structure of JSON or JSON-Lines data is valuable when working with large datasets or debugging issues. Outputting the schema helps identify the available keys and their types.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• -s is the argument to instruct jello to output the schema of the JSON data.

Example Output:

{
    "key1": "string",
    "key2": "number"
}

Output all elements from arrays or all values from objects

Code:

cat file.json | jello -l

Motivation:

In some cases, it’s necessary to extract all the elements from arrays or all the values from objects in JSON or JSON-Lines data. This can be useful for further processing or analysis.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• -l is the argument to instruct jello to output all elements from arrays or all values from objects.

Example Output:

"value1"
"value2"
"value3"
"value4"

Output the first element

Code:

cat file.json | jello _[0]

Motivation:

In scenarios where only the first element of JSON or JSON-Lines data is needed, extracting it can help reduce unnecessary processing or focus on essential information.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• _[0] is an expression that extracts the first element (index 0) from the input data.

Example Output:

{
    "key1": "value1",
    "key2": "value2"
}

Output the value of a given key for each element

Code:

cat file.json | jello '[i.key_name for i in _]'

Motivation:

When specific information needs to be extracted from each element in a JSON array or JSON-Lines data, it can be useful to output the values of a particular key. This facilitates processing or analysis based on that key’s value.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• [i.key_name for i in _] is a list comprehension that extracts the value of the key key_name for each element in the JSON data.

Example Output:

"value1"
"value2"

Output the value of multiple keys as a new JSON object

Code:

cat file.json | jello '{"my_new_key": _.key_name, "my_other_key": _.other_key_name}'

Motivation:

In scenarios where a new JSON object needs to be created from existing keys, combining and renaming them, this command can be useful. It allows for generating a JSON object with specific key-value pairs based on the existing data.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• {"my_new_key": _.key_name, "my_other_key": _.other_key_name} is a JSON object that creates new keys my_new_key and my_other_key with corresponding values extracted from the original JSON data.

Example Output:

{
    "my_new_key": "value1",
    "my_other_key": "value2"
}

Output the value of a given key to a string (and disable JSON output)

Code:

cat file.json | jello -r '"some text: " + _.key_name'

Motivation:

In certain cases, it may be necessary to concatenate the value of a given key with a string or perform a custom operation. This command allows for more flexibility in manipulating the data and generating customized output.

Explanation:

• cat file.json reads the contents of the file.json file.
• | is the pipe operator, which takes the output from the previous command and passes it as input to the next command.
• jello is the command-line JSON processor.
• -r is the argument to instruct jello to disable the default JSON output and instead print a string.
• '"some text: " + _.key_name' is a string concatenation expression that combines the value of the key key_name with the text “some text”.

Example Output:

"some text: value1"

By understanding and utilizing the various functionalities of the jello command-line JSON processor, you can effectively manipulate, extract, and transform JSON or JSON-Lines data to meet your specific needs. Whether it’s for readability, analysis, or data transformation, jello provides a flexible and powerful tool for working with JSON data.