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BLAKE3/b3sum/README.md
Jack O'Connor 0db6fddc86 version 0.3.3
Changes since 0.3.2:
- `b3sum` binaries are built in CI and attached to new GitHub tags.
2020-04-28 11:20:39 -04:00

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2.4 KiB
Markdown

# b3sum
A command line utility for calculating
[BLAKE3](https://github.com/BLAKE3-team/BLAKE3) hashes, similar to
Coreutils tools like `b2sum` or `md5sum`.
```
b3sum 0.3.3
USAGE:
b3sum [FLAGS] [OPTIONS] [file]...
FLAGS:
-h, --help Prints help information
--keyed Uses the keyed mode. The secret key is read from standard
input, and it must be exactly 32 raw bytes.
--no-mmap Disables memory mapping
--no-names Omits filenames in the output
--raw Writes raw output bytes to stdout, rather than hex.
--no-names is implied. In this case, only a single
input is allowed.
-V, --version Prints version information
OPTIONS:
--derive-key <CONTEXT> Uses the key derivation mode, with the given
context string. Cannot be used with --keyed.
-l, --length <LEN> The number of output bytes, prior to hex
encoding (default 32)
--num-threads <NUM> The maximum number of threads to use. By
default, this is the number of logical cores.
If this flag is omitted, or if its value is 0,
RAYON_NUM_THREADS is also respected.
ARGS:
<file>...
```
# 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
The standard way to install `b3sum` is:
```
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`.
By default, `b3sum` enables the assembly implementations, AVX-512
support, and multi-threading features of the underlying
[`blake3`](https://crates.io/crates/blake3) crate. To avoid this (for
example, if your C compiler does not support AVX-512), you can use
Cargo's `--no-default-features` flag.