b3sum

A command line utility for calculating BLAKE3 hashes, similar to Coreutils tools like b2sum or md5sum.

``` Usage: b3sum [OPTIONS] [FILE]...

Arguments: [FILE]... Files to hash, or checkfiles to check

Options: -l, --length The number of output bytes, before hex encoding [default: 32] --num-threads The maximum number of threads to use --keyed Use the keyed mode --derive-key Use the key derivation mode, with the given context string --no-mmap Disable memory mapping --no-names Omit filenames in the output --raw Write raw output bytes to stdout, rather than hex -c, --check Read BLAKE3 sums from the [FILE]s and check them --quiet Skip printing OK for each successfully verified file -h, --help Print help information (use --help for more detail) -V, --version Print version information ```

See also this document about how the --check flag works.

Example

Hash the file foo.txt:

bash b3sum foo.txt

Time hashing a gigabyte of data, to see how fast it is:

```bash

Create a 1 GB file.

head -c 1000000000 /dev/zero > /tmp/bigfile

Hash it with SHA-256.

time openssl sha256 /tmp/bigfile

Hash it with BLAKE3.

time b3sum /tmp/bigfile ```

Installation

Prebuilt binaries are available for Linux, Windows, and macOS (requiring the unidentified developer workaround) on the releases page. If you've installed Rust and Cargo, you can also build b3sum yourself with:

cargo install b3sum

On Linux for example, Cargo will put the compiled binary in ~/.cargo/bin. You might want to add that directory to your $PATH, or rustup might have done it for you when you installed Cargo.

If you want to install directly from this directory, you can run cargo install --path .. Or you can just build with cargo build --release, which puts the binary at ./target/release/b3sum.