Introduction

zentropy is a tool to measure a file's Shannon entropy, which gives useful information such as theoretical minimum size, but also helpful in identifying specific kinds of files.

Note, various compression algorithms can reach sizes smaller than the one given by calculating Shannon entropy, as Shannon entropy assumes a statistical model where the bytes are uncorrelated (i.e: 0 order).

Usage

Fairly straightforward, point it at a file!

$ zentropy /path/to/file

Here's the output of running it against the project's build.zig:

$ zentropy ./build.zig 

------------
| zentropy |
------------
entropy            => 0.55 nats
entropy (bits)     => 4.36 bits
file size          => 1.59 Kib
possible file size => 887.35 bytes
compression        => 45.49 %

Installation

Get a precompiled binary from the release page or build your own with zig!

Special steps

On both Linux and Mac, don't forget to chmod +x /path/to/binary.

Mac might yell at you for trying to run the binary, in which case, just run:

$ xattr -d com.apple.quarantine /path/to/binary

Supported platforms

So far, it's only been tested on:

arch	os
x86_64	windows
x86_64	linux
x86_64	mac os

Roadmap

Some things on the roadmap / to-do list when I have some time:

• support wasm
• JSON output
• wrap in a Docker container
• allow setting chunk size via env var or cli flag