A simple cross platform library for writing colored text to a terminal. This library writes colored text either using standard ANSI escape sequences or by interacting with the Windows console. Several convenient abstractions are provided for use in single-threaded or multi-threaded command line applications.
Dual-licensed under MIT or the UNLICENSE.
Add this to your Cargo.toml
:
[dependencies]
termcolor = "1.1"
The WriteColor
trait extends the io::Write
trait with methods for setting
colors or resetting them.
StandardStream
and StandardStreamLock
both satisfy WriteColor
and are
analogous to std::io::Stdout
and std::io::StdoutLock
, or std::io::Stderr
and std::io::StderrLock
.
Buffer
is an in memory buffer that supports colored text. In a parallel
program, each thread might write to its own buffer. A buffer can be printed to
stdout or stderr using a BufferWriter
. The advantage of this design is that
each thread can work in parallel on a buffer without having to synchronize
access to global resources such as the Windows console. Moreover, this design
also prevents interleaving of buffer output.
Ansi
and NoColor
both satisfy WriteColor
for arbitrary implementors of
io::Write
. These types are useful when you know exactly what you need. An
analogous type for the Windows console is not provided since it cannot exist.
The StandardStream
type in this crate works similarly to std::io::Stdout
,
except it is augmented with methods for coloring by the WriteColor
trait.
For example, to write some green text:
use std::io::{self, Write};
use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
fn write_green() -> io::Result<()> {
let mut stdout = StandardStream::stdout(ColorChoice::Always);
stdout.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
writeln!(&mut stdout, "green text!")
}
A BufferWriter
can create buffers and write buffers to stdout or stderr. It
does not implement io::Write
or WriteColor
itself. Instead, Buffer
implements io::Write
and termcolor::WriteColor
.
This example shows how to print some green text to stderr.
use std::io::{self, Write};
use termcolor::{BufferWriter, Color, ColorChoice, ColorSpec, WriteColor};
fn write_green() -> io::Result<()> {
let mut bufwtr = BufferWriter::stderr(ColorChoice::Always);
let mut buffer = bufwtr.buffer();
buffer.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
writeln!(&mut buffer, "green text!")?;
bufwtr.print(&buffer)
}
When building a writer with termcolor, the caller must provide a
ColorChoice
selection. When the color choice is Auto
, termcolor will attempt to determine
whether colors should be enabled by inspecting the environment. Currently,
termcolor will inspect the TERM
and NO_COLOR
environment variables:
- If
NO_COLOR
is set to any value, then colors will be suppressed. - If
TERM
is set todumb
, then colors will be suppressed. - In non-Windows environments, if
TERM
is not set, then colors will be suppressed.
This decision procedure may change over time.
Currently, termcolor
does not attempt to detect whether a tty is present or
not. To achieve that, please use the atty
crate.
This crate's minimum supported rustc
version is 1.34.0
.
The current policy is that the minimum Rust version required to use this crate
can be increased in minor version updates. For example, if crate 1.0
requires
Rust 1.20.0, then crate 1.0.z
for all values of z
will also require Rust
1.20.0 or newer. However, crate 1.y
for y > 0
may require a newer minimum
version of Rust.
In general, this crate will be conservative with respect to the minimum supported version of Rust.