111 lines
4.3 KiB
Markdown
111 lines
4.3 KiB
Markdown
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termcolor
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=========
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A simple cross platform library for writing colored text to a terminal. This
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library writes colored text either using standard ANSI escape sequences or by
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interacting with the Windows console. Several convenient abstractions are
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provided for use in single-threaded or multi-threaded command line
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applications.
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[](https://github.com/BurntSushi/termcolor/actions)
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[](https://crates.io/crates/termcolor)
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Dual-licensed under MIT or the [UNLICENSE](https://unlicense.org/).
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### Documentation
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[https://docs.rs/termcolor](https://docs.rs/termcolor)
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### Usage
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Run `cargo add termcolor` to add this dependency to your `Cargo.toml` file.
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### Organization
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The `WriteColor` trait extends the `io::Write` trait with methods for setting
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colors or resetting them.
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`StandardStream` and `StandardStreamLock` both satisfy `WriteColor` and are
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analogous to `std::io::Stdout` and `std::io::StdoutLock`, or `std::io::Stderr`
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and `std::io::StderrLock`.
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`Buffer` is an in memory buffer that supports colored text. In a parallel
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program, each thread might write to its own buffer. A buffer can be printed to
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stdout or stderr using a `BufferWriter`. The advantage of this design is that
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each thread can work in parallel on a buffer without having to synchronize
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access to global resources such as the Windows console. Moreover, this design
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also prevents interleaving of buffer output.
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`Ansi` and `NoColor` both satisfy `WriteColor` for arbitrary implementors of
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`io::Write`. These types are useful when you know exactly what you need. An
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analogous type for the Windows console is not provided since it cannot exist.
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### Example: using `StandardStream`
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The `StandardStream` type in this crate works similarly to `std::io::Stdout`,
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except it is augmented with methods for coloring by the `WriteColor` trait. For
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example, to write some green text:
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```rust
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use std::io::{self, Write};
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use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
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fn write_green() -> io::Result<()> {
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let mut stdout = StandardStream::stdout(ColorChoice::Always);
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stdout.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
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writeln!(&mut stdout, "green text!")
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}
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```
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### Example: using `BufferWriter`
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A `BufferWriter` can create buffers and write buffers to stdout or stderr. It
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does *not* implement `io::Write` or `WriteColor` itself. Instead, `Buffer`
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implements `io::Write` and `termcolor::WriteColor`.
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This example shows how to print some green text to stderr.
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```rust
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use std::io::{self, Write};
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use termcolor::{BufferWriter, Color, ColorChoice, ColorSpec, WriteColor};
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fn write_green() -> io::Result<()> {
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let mut bufwtr = BufferWriter::stderr(ColorChoice::Always);
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let mut buffer = bufwtr.buffer();
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buffer.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
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writeln!(&mut buffer, "green text!")?;
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bufwtr.print(&buffer)
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}
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```
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### Automatic color selection
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When building a writer with termcolor, the caller must provide a
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[`ColorChoice`](https://docs.rs/termcolor/1.*/termcolor/enum.ColorChoice.html)
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selection. When the color choice is `Auto`, termcolor will attempt to determine
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whether colors should be enabled by inspecting the environment. Currently,
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termcolor will inspect the `TERM` and `NO_COLOR` environment variables:
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* If `NO_COLOR` is set to any value, then colors will be suppressed.
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* If `TERM` is set to `dumb`, then colors will be suppressed.
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* In non-Windows environments, if `TERM` is not set, then colors will be
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suppressed.
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This decision procedure may change over time.
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Currently, `termcolor` does not attempt to detect whether a tty is present or
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not. To achieve that, please use
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[`std::io::IsTerminal`](https://doc.rust-lang.org/std/io/trait.IsTerminal.html).
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### Minimum Rust version policy
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This crate's minimum supported `rustc` version is `1.34.0`.
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The current policy is that the minimum Rust version required to use this crate
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can be increased in minor version updates. For example, if `crate 1.0` requires
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Rust 1.20.0, then `crate 1.0.z` for all values of `z` will also require Rust
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1.20.0 or newer. However, `crate 1.y` for `y > 0` may require a newer minimum
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version of Rust.
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In general, this crate will be conservative with respect to the minimum
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supported version of Rust.
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