Generate human readable random names.

🚨 UPGRADING FROM 1.x? There are several breaking changes; please read the notes.

Petnames are useful when you need to name a large number of resources – like servers, services, perhaps bicycles for hire – and you want those names to be easy to recall and communicate unambiguously. For example, over a telephone compare saying "please restart remarkably-striking-cricket" with "please restart s01O97i4": the former is easier to say and less likely to be misunderstood. Avoiding sequential names adds confidence too: petnames have a greater lexical distance between them, so errors in transcription can be more readily detected.

This crate is both a command-line tool and a Rust library. Dustin Kirkland's petname project is the inspiration for this project. The word lists and the basic command-line UX here are taken from there. Check it out! Dustin maintains packages for Python, and Golang too.

Notable features:

• Choose from 3 built-in word lists, or provide your own.
• Alliterative names, like viable-vulture, proper-pony, ...
• Build names with 1-255 components (adjectives, adverbs, nouns).
• Name components can be unseparated, or joined by any character or string.
• Generate 1..n names, or stream names continuously.
• no_std support (see later section).
• Compile without built-in dictionaries to reduce library/binary size.

If you have installed Cargo, you can install rust-petname with cargo install petname. This puts a petname binary in ~/.cargo/bin, which the Cargo installation process will probably have added to your PATH.

The petname binary from rust-petname is mostly drop-in compatible with the original petname. It has more options and it's stricter when validating arguments, but for most uses it should behave the same¹.

$ petname -h
Generate human readable random names

Usage: petname [OPTIONS]

Options:
  -w, --words <WORDS>             Number of words in name [default: 2]
  -s, --separator <SEP>           Separator between words [default: -]
      --lists <LIST>              Use the built-in word lists with small, medium, or large words [default: medium] [possible values: small, medium, large]
  -c, --complexity <NUM>          Alias for compatibility with upstream; prefer --lists instead
  -d, --dir <DIR>                 Use custom word lists by specifying a directory containing `adjectives.txt`, `adverbs.txt`, and `nouns.txt`
      --count <COUNT>             Generate multiple names; or use --stream to generate continuously [default: 1]
      --stream                    Stream names continuously
  -l, --letters <LETTERS>         Maximum number of letters in each word; 0 for unlimited [default: 0]
  -a, --alliterate                Generate names where each word begins with the same letter
  -A, --alliterate-with <LETTER>  Generate names where each word begins with the given letter
  -u, --ubuntu                    Alias for compatibility with upstream; prefer --alliterate instead
      --seed <SEED>               Seed the RNG with this value (unsigned 64-bit integer in base-10)
  -h, --help                      Print help (see more with '--help')
  -V, --version                   Print version

Based on Dustin Kirkland's petname project <https://github.com/dustinkirkland/petname>.

$ petname
unified-platypus

$ petname -s _ -w 3
lovely_notable_rooster

This implementation is considerably faster than the upstream petname:

$ time /usr/bin/petname
fit-lark

real    0m0.038s
user    0m0.032s
sys     0m0.008s

$ time target/release/petname
cool-guinea

real    0m0.002s
user    0m0.002s
sys     0m0.000s

These timings are irrelevant if you only need to name a single thing, but if you need to generate 100s or 1000s of names then rust-petname is handy:

$ time { for i in $(seq 1000); do /usr/bin/petname; done; } > /dev/null

real    0m32.058s
user    0m29.360s
sys     0m5.163s

$ time { for i in $(seq 1000); do target/release/petname; done; } > /dev/null

real    0m2.199s
user    0m1.333s
sys     0m0.987s

To be fair, /usr/bin/petname is a shell script. The Go command-line version (available from the golang-petname package on Ubuntu) is comparable to the Rust version for speed, but has very limited options compared to its shell-script ancestor and to rust-petname.

Lastly, rust-petname has a --count option that speeds up generation of names considerably:

$ time target/release/petname --count=10000000 > /dev/null

real    0m1.327s
user    0m1.322s
sys     0m0.004s

That's ~240,000 (two hundred and forty thousand) times faster, for about 7.5 million petnames a second on this hardware. This is useful if you want to apply an external filter to the names being generated:

$ petname --words=3 --stream | grep 'love.*\bsalmon$'

You can use rust-petname in your own Rust projects with cargo add petname.

There are a few features that can be selected – or, more correctly, deselected, since all features are enabled by default:

• default-rng enables std and std_rng in rand. A couple of convenience functions depend on this for a default RNG.
• default-words enables the default word lists. Deselecting this will reduce the size of compiled artifacts.
• clap enables the clap command-line argument parser, which is needed to build the petname binary.
  • NOTE that clap is not necessary for the library at all, and you can deselect it, but it is presently a default feature since otherwise it's inconvenient to build the binary. This will probably change in the future.

All of these are required to build the command-line utility.

The library can be built without any default features, and it will work in a no_std environment, like Wasm. You'll need to figure out a source of randomness, but SmallRng::seed_from_u64 may be a good starting point.

Version 2.0 brought several breaking changes to both the API and the command-line too. Below are the most important:

• The --complexity <COMPLEXITY> option has been replaced by --lists <LISTS>.
  • For compatibility, --complexity [0,1,2] will still work, but its availability is not shown in the -h|--help text.
  • The default is now "medium" (equivalent to --complexity 1). Previously it was "small" (--complexity 0).
• When using custom word lists with --dir <DIR>, nouns are now found in a file named appropriately DIR/nouns.txt. Previously this was names.txt but this was confusing; the term "names" is overloaded enough already.
  • For compatibility, if nouns.txt is not found, an attempt will be made to load nouns from names.txt.
• The option --count 0 is no longer a synonym for --stream. Use --stream instead. It's not an error to pass --count 0, but it will result in zero names being generated.
• The --non-repeating flag is no longer recognised (#101).

• Feature flags have been renamed:
  • std_rng is now default-rng,
  • default_dictionary is now default-words.
• The names field on the Petnames struct has been renamed to nouns.
• Petnames::new() is now Petnames::default().
• Petnames::new(…) now accepts word lists as strings.
• Names is no longer public. This served as the iterator struct returned by Petnames::iter(…), but this now hides the implementation details by returning impl Iterator<Item = String> instead. This also means that Names::cardinality(&self) is no longer available; use Petnames::cardinality(&self, words: u8) instead.
• Petnames::iter_non_repeating has been removed (#101).
• Petnames::generate, Petnames::generate_one, and Petnames::iter have been extracted into a Generator trait. This must be in scope in order to call those methods (#102).
• The default word lists are now the "medium" lists.

To hack the source:

• Install Cargo,
• Clone this repository,
• Build it: cargo build.
• Optionally, hide noise when using git blame: git config blame.ignoreRevsFile .git-blame-ignore-revs.

After installing the source (see above) run tests with: cargo test.

1. Bump version in Cargo.toml.
2. Paste updated -h output into README.md (this file; see near the top). On macOS the command cargo run -- -h | pbcopy is helpful. Note that --help output is not the same as -h output: it's more verbose and too much for an overview.
3. Build and test. The latter on its own does do a build, but a test build can hide warnings about dead code, so do both.
   • With default features: cargo build && cargo test
   • Without: cargo build --no-default-features && cargo test --no-default-features
4. Commit with message "Bump version to $VERSION."
5. Tag with "v$VERSION", e.g. git tag v1.0.10.
6. Push: git push && git push --tags.
7. Publish: cargo publish.

This project is licensed under the Apache 2.0 License. See the LICENSE file for details.