fish-shell/printf/README.md
2024-09-23 11:16:42 -07:00

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# fish-printf
The printf implementation used in [fish-shell](https://fishshell.com), based on musl printf.
[![crates.io](https://img.shields.io/crates/v/fish-printf.svg)](https://crates.io/crates/fish-printf)
Licensed under the MIT license.
### Usage
Run `cargo add fish-printf` to add this crate to your `Cargo.toml` file.
### Notes
fish-printf attempts to match the C standard for printf. It supports the following features:
- Locale-specific formatting (decimal point, thousands separator, etc.)
- Honors the current rounding mode.
- Supports the `%n` modifier for counting characters written.
fish-printf does not support positional arguments, such as `printf("%2$d", 1, 2)`.
Prefixes like `l` or `ll` are recognized, but only used for validating the format string.
The size of integer values is taken from the argument type.
fish-printf can output to an `std::fmt::Write` object, or return a string.
For reasons related to fish-shell, fish-printf has a feature "widestring" which uses the [widestring](https://crates.io/crates/widestring) crate. This is off by default. If enabled, run `cargo add widestring` to add the widestring crate.
### Examples
```rust
use fish_printf::sprintf;
// Create a `String` from a format string.
let s = sprintf!("%0.5g", 123456.0) // 1.2346e+05
// Append to an existing string.
let mut s = String::new();
sprintf!(=> &mut s, "%0.5g", 123456.0) // 1.2346e+05
```
See the crate documentation for additional examples.