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utt is the universal text transformer. utt is intended for converting between textual data representations. For example, utt can be used to convert from JSON to YAML:

$ echo "[1, 2, 3]" | utt -i json -o yaml
- 1
- 2
- 3


Formats may be supported for input-only or output-only. You can see all supported formats by running utt with no arguments.

At the time of writing, supported formats are:

  • JSON
  • XML
  • CSV
  • YAML
  • Java Properties
  • TOML
  • Base 64
  • Plain Text
  • ROT13
  • PyON (Python Object Notation)

Note: "universal" is a big claim, and I understand that utt isn't truly universal. However, it is an active goal to work on supporting more and more formats and transformations to make utt as close to truly universal as possible.

Getting it

A UNIX-compatible binary is automatically released here: This binary is just:

$ echo "#!/usr/bin/env -S java -jar" > utt && cat utt-*.jar >> utt && chmod +x utt

On Windows, run mvn clean package to create a JAR file in target/.

Why is it so big???

Unfortunately, supporting everything under the sun requires dragging in a pretty ridiculous set of libraries. For example, to support Python dict notation, utt drags in an entire Python implementation via jython-standalone.

What and why

utt (case-sensitive) is a tool for converting between textual data formats. utt was originally written for a project that involved a lot of annoying conversions, to the point where one-off scripts wouldn't be enough.

utt makes some tradeoffs in the name of functionality. For example, utt does not process data in a streaming manner, but rather loads the entire dataset into memory before processing. In exchange, utt is more flexible in what it accepts as input and output formats. For example, utt can only output to CSV by iterating over the input data to determine the output schema. Similarly, utt's mapping functionality relies on the GraalVM Polyglot API, which has a high (~500ms) startup time.

While pandoc focuses more on converting between human formats like markdown and HTML, utt is more focused on converting between data formats understood by computers.


Convert from JSON to YAML

$ echo '{"key": [1, 2, 3]}' | utt -i json -o yaml
- 1
- 2
- 3


Extract keys from a JSON object

$ echo '[{"key": 1}, {"key": 2}, {"key": 3}]' | utt -i json -o json -M '_.key'

Flatten a list

$ echo '[[1], [2], [3]]' | utt -i json -o json -F

Encode text with base64

$ echo "this is a test" | utt -i plain -o base64

Extract inner values and flatten

$ echo '{"key": [1, [2], [[3]]]}' | utt -i json -o json -M '_.key' -F

Extract a JSON array from an XML object

$ echo "<a><b>c</b><b>c</b><b>c</b><b>c</b></a>" | utt -i xml -o json -M '$.b'

Apply a map function to the values of a list

$ echo "[1,2,3]" | utt -i json -o yaml -M "_ * 2"
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- 6.0