Using lupdate

The lupdate command line tool finds translatable strings in C++ source, C++ header, Java, Python, QML, and UI files and generates or updates TS files.

When building with qmake, specify the files to process at the command line or in a .pro file.

When building with CMake, use CMake commands to add targets that create or update TS files and transform them into QM files. The lupdate tool is run with the options you pass to the commands when you build the target.

For more information about specifying translations in project files, see Localizing Applications.

lupdate syntax

lupdate [options] [project-file]...
lupdate [options] [source-file|path|@lst-file]... -ts ts-files|@lst-file

Where:

• options means one or several lupdate options.
• project-file is the project configuration file.
• source-file is a file that contains translatable strings.
• path is the path to a folder that contains translation source files.
• @lst-file reads additional file names (one per line) or includepaths (one per line and prefixed with -I) from lst-file.
• ts-files are the TS files to generate or update.

To view the latest help, enter:

lupdate -help

lupdate options

Examples

Using lupdate with CMake

When building with CMake, use CMake commands to add translations on targets to the CMakeLists.txt file, and then build the targets.

Select one of the following options:

• Use qt_add_translations on a target, such as app. This calls qt_add_lupdate and qt_add_lrelease.
• Use qt_add_lupdate on a target.

Build a target (for example, app_lupdate) to update the .ts files for it. To update the .ts files for all targets, build the target update_translations.

Using lupdate with qmake

To generate a translation file for a single QML file:

lupdate main.qml -ts main_en.ts

To make a translation file for another language, for example French, copy main_en.ts to main_fr.ts, and translate the strings in the French TS file.

lupdate processes QML files that are listed in the .qrc file:

RESOURCES += qml.qrc

To have all QML files processed by lupdate:

lupdate application.qrc -ts myapp_en.ts

To process all QML files in the current working directory (or its subfolders) without using a .qrc file:

lupdate . -extensions qml -ts myapp_en.ts

To check for translatable strings in both QML and C++ source files:

lupdate qml.qrc filevalidator.cpp -ts myapp_en.ts

To generate .ts files that will be used for English and French without specifying the languages in the project file:

lupdate qml.qrc filevalidator.cpp -ts myapp_en.ts myapp_fr.ts

Give the TS files to the translator who uses Qt Linguist to read the files and insert the translations.

XLIFF format files

The TS file format is a simple human-readable XML format that you can use with version control systems. In addition, lupdate can process Localization Interchange File Format (XLIFF) files (.xlf).

You can open and edit XLIFF files in Qt Linguist.