Textwrap is a small Rust crate for word wrapping text. You can use it to format strings for display in commandline applications. The crate name and interface is inspired by the Python textwrap module.
To use textwrap, add this to your Cargo.toml file:
[dependencies] textwrap = "0.12"
This gives you the text wrapping without of the optional features listed next.
hyphenationIf you would like to have automatic language-sensitive hyphenation, enable the hyphenation feature:
[dependencies] textwrap = { version = "0.12", features = ["hyphenation"] }
This gives you hyphenation support for US English. Please see the hyphenation example for an executable demo. Read the Getting Started section below to see how to load the hyphenation patterns for other languages.
terminal_sizeTo conveniently wrap text at the current terminal width, enable the terminal_size feature:
[dependencies] textwrap = { version = "0.12", features = ["terminal_size"] }
Please see the termwidth example for how to use this feature.
Word wrapping single strings is easy using the fill function:
fn main() { let text = "textwrap: a small library for wrapping text."; println!("{}", textwrap::fill(text, 18)); }
The output is
textwrap: a small library for wrapping text.
If you enable the hyphenation feature, you get support for automatic hyphenation for about 70 languages via high-quality TeX hyphenation patterns.
Your program must load the hyphenation pattern and call Wrapper::with_splitter to use it:
use hyphenation::{Language, Load, Standard}; use textwrap::Wrapper; fn main() { let hyphenator = Standard::from_embedded(Language::EnglishUS).unwrap(); let wrapper = Wrapper::with_splitter(18, hyphenator); let text = "textwrap: a small library for wrapping text."; println!("{}", wrapper.fill(text)) }
The output now looks like this:
textwrap: a small library for wrap- ping text.
The US-English hyphenation patterns are embedded when you enable the hyphenation feature. They are licensed under a permissive license and take up about 88 KB of space in your application. If you need hyphenation for other languages, you need to download a precompiled .bincode file and load it yourself. Please see the hyphenation documentation for details.
The library comes with some small example programs that shows various features.
The layout example shows how a fixed example string is wrapped at different widths. Run the example with:
$ cargo run --features hyphenation --example layout
The program will use the following string:
Memory safety without garbage collection. Concurrency without data races. Zero-cost abstractions.
The string is wrapped at all widths between 15 and 60 columns. With narrow columns the output looks like this:
.--- Width: 15 ---. | Memory safety | | without garbage | | collection. | | Concurrency | | without data | | races. Zero- | | cost abstrac- | | tions. | .--- Width: 16 ----. | Memory safety | | without garbage | | collection. Con- | | currency without | | data races. Ze- | | ro-cost abstrac- | | tions. |
Later, longer lines are used and the output now looks like this:
.-------------------- Width: 49 --------------------. | Memory safety without garbage collection. Concur- | | rency without data races. Zero-cost abstractions. | .---------------------- Width: 53 ----------------------. | Memory safety without garbage collection. Concurrency | | without data races. Zero-cost abstractions. | .------------------------- Width: 59 -------------------------. | Memory safety without garbage collection. Concurrency with- | | out data races. Zero-cost abstractions. |
Notice how words are split at hyphens (such as “zero-cost”) but also how words are hyphenated using automatic/machine hyphenation.
The termwidth example simply shows how the width can be set automatically to the current terminal width. Run it with this command:
$ cargo run --example termwidth
If you run it in a narrow terminal, you'll see output like this:
Formatted in within 60 columns: ---- Memory safety without garbage collection. Concurrency without data races. Zero-cost abstractions. ----
If stdout is not connected to the terminal, the program will use a default of 80 columns for the width:
$ cargo run --example termwidth | cat Formatted in within 80 columns: ---- Memory safety without garbage collection. Concurrency without data races. Zero- cost abstractions. ----
This section lists the largest changes per release.
The code has been updated to the Rust 2018 edition and each new release of textwrap will only support the latest stable version of Rust. Trying to support older Rust versions is a fool's errand: our dependencies keep releasing new patch versions that require newer and newer versions of Rust.
The term_size feature has been replaced by terminal_size. The API is unchanged, it is just the name of the Cargo feature that changed.
The hyphenation feature now only embeds the hyphenation patterns for US-English. This slims down the dependency.
Due to our dependencies bumping their minimum supported version of Rust, the minimum version of Rust we test against is now 1.22.0.
dedent handling of empty lines and trailing newlines. Thanks @bbqsrc!Due to our dependencies bumping their minimum supported version of Rust, the minimum version of Rust we test against is now 1.17.0.
The dependency on term_size is now optional, and by default this feature is not enabled. This is a breaking change for users of Wrapper::with_termwidth. Enable the term_size feature to restore the old functionality.
Added a regression test for the case where width is set to usize::MAX, thanks @Fraser999! All public structs now implement Debug, thanks @hcpl!
term_size an optional dependency.The Wrapper stuct is now generic over the type of word splitter being used. This means less boxing and a nicer API. The Wrapper::word_splitter method has been removed. This is a breaking API change if you used the method to change the word splitter.
The Wrapper struct has two new methods that will wrap the input text lazily: Wrapper::wrap_iter and Wrapper::into_wrap_iter. Use those if you will be iterating over the wrapped lines one by one.
Version 0.7.0 changes the return type of Wrapper::wrap from Vec<String> to Vec<Cow<'a, str>>. This means that the output lines borrow data from the input string. This is a breaking API change if you relied on the exact return type of Wrapper::wrap. Callers of the textwrap::fill convenience function will see no breakage.
The above change and other optimizations makes version 0.7.0 roughly 15-30% faster than version 0.6.0.
The squeeze_whitespace option has been removed since it was complicating the above optimization. Let us know if this option is important for you so we can provide a work around.
Version 0.6.0 adds builder methods to Wrapper for easy one-line initialization and configuration:
let wrapper = Wrapper::new(60).break_words(false);
It also add a new NoHyphenation word splitter that will never split words, not even at existing hyphens.
Version 0.5.0 has breaking API changes. However, this only affects code using the hyphenation feature. The feature is now optional, so you will first need to enable the hyphenation feature as described above. Afterwards, please change your code from
wrapper.corpus = Some(&corpus);
to
wrapper.splitter = Box::new(corpus);
Other changes include optimizations, so version 0.5.0 is roughly 10-15% faster than version 0.4.0.
self.width.hyphenation.Documented complexities and tested these via cargo bench.
Added support for automatic hyphenation.
Introduced Wrapper struct. Added support for wrapping on hyphens.
First public release with support for wrapping strings on whitespace.
Textwrap can be distributed according to the MIT license. Contributions will be accepted under the same license.