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#41 in Internationalization (i18n)

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Localisation of rust applications

Travis Build Status

This repository is an attempt to make it possible to localize rust application. There are two crates

  • tr is a runtime library wrapping gettext (currently), in order to provide a convenient way to localize an application.

  • xtr is a binary similar to GNU's xgettext which extract string from a rust crate. It can extract strings of crate using the tr macro from this sibling crate, or using other gettext based localisation crates such as gettext-rs, gettext, rocket_i18n

How to translate a rust application

  1. Annotate the strings in your source code with the write macro/functions. You can use

    • The the tr! macro from this tr crate (still work in progress), or
    • The gettext function from the gettext or the gettext-rs crate
  2. Run the xtr program over your crate to extract the string in a .pot file

  3. Use the GNU gettext tools to merge, translate, and generate the .mo files

About tr!

  • The name comes from Qt's tr() function. It is a short name since it will be placed on most string literal.
  • The macro can do rust-style formatting. This makes it possible to re-order the arguments in the translations.
  • Hello {} or Hello {0} or Hello Hello {name} works.
  • Currently, the default backend uses the gettext-rs crate, but this could be changed to gettext in the future.
  • Plurals are handled by gettext, which support the different plurals forms of several languages.

Future plans

  • Validity of the formatting in the original or translation is not done yet, but could be done in the future
  • More advanced formatting that would allow for gender or case can be done as an extension to the formatting rules. Since the macro takes the arguments directly, it will be possible to extend the formatting engine with a scripting system or something like ICU MessageFormat.
  • Formatting date/number in a localized fashion.


extern crate tr;
fn main() {
    // use the tr_init macro to tell gettext where to look for translations
    let folder = if let Some(folder) = std::env::args().nth(1) {
    } else {
        println!("{}", tr!("Please give folder name"));
    match std::fs::read_dir(&folder) {
        Err(e) => {
            println!("{}", tr!("Could not read directory '{}'\nError: {}",
                                folder, e));
        Ok(r) => {
            // Singlular/plural formating
            println!("{}", tr!(
                "The directory {} has one file" | "The directory {} has {n} files" % r.count(),

About xtr

xtr is a tool that extract translated strings from the source code of a rust crate. The tool is supposed to be compatible with any gettext based functions. But support for the special syntax of the tr! macro has been added.


xtr src/main.rs -o example.pot

This will extract the strings from all the modules of the crate, and create a file example.pot. You can now use the gettext tools to translate this file.

Differences with xgettext

xtr is basically to be used in place of xgettext for Rust code. xgettext does not currently support the rust language. We can get decent result using the C language, but:

  • xgettext will not work properly if the code contains comments or string escaping that is not compatible with Rust's rules. (Rules for comments, or string escaping are different in Rust and in C. Think about raw literal, embedded comments, lifetime, ...) xtr uses the lexer from the proc_macro2 crate so it parse rust code.
  • xgettext cannot be told to extract string out of a macro, while xtr will ignore the ! token. So gettext(...) or gettext!(...) will work.
  • xgettext cannot handle the rust rules within the string literal. xtr will have no problem with rust's raw literal or rust's escape sequence.
  • xtr can also parse the mod keyword, and easily parse all the files in a crate.
  • Finally, xtr can also parse the more advanced syntax within the tr! macro.



Contributions are welcome. Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, should be licensed under the MIT license.

Request for feedback

Please fill your suggestions as issues. Or help by commenting on https://github.com/woboq/tr/issues/1


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