Build multi-language support into your Linux application with catgets

Putting It All Together

Listing 2 shows how to use catgets in a sample C program. The program first needs to open the catalog file using catopen(). For every string the program needs to print, I first need to retrieve the string from the catalog using catgets(). When the program is done using the catalog, a call to the catclose() function closes it.

Listing 2

A Sample Program

 

Now when you compile and run the program, you will see the Klingon text nuqneH instead of the default text Hello.

$ gcc -o hello hello.o
$ ./hello
nuqneH

Extending the Program

In this article, I have described a simple example with a hard-coded path to the catalog file. To make this example more flexible, and to support multiple spoken languages, you can omit the path to the message catalog in the catopen() function call and allow the program to look for a catalog file in some location defined by the system (Listing 3).

Listing 3

Omitting the Path

 

With this change, when you compile and run the new program, you can let the NLSPATH environment variable determine where catopen() will find the message catalog file. The NLSPATH variable uses certain flags to stand in for other values, such as %N for "the file itself." Let's say you set the NLSPATH variable as NLSPATH=/path/to/messages/%N. When you run the program, it will look for the hello.cat message file as /path/to/messages/hello.cat.

Infos

  1. catgets() – Retrieve a Message from a Message Catalog: https://www.ibm.com/docs/en/i/7.3?topic=functions-catgets-retrieve-message-from-message-catalog
  2. The message catalog files (the GNU C Library): https://www.gnu.org/software/libc/manual/html_node/The-message-catalog-files.html
  3. The gencat program (the GNU C Library): https://www.gnu.org/software/libc/manual/html_node/The-gencat-program.html

The Author

Jim Hall is an open source software advocate and developer, best known for usability testing in Gnome and as the founder and project coordinator of FreeDOS. At work, Jim is CEO of Hallmentum, an IT executive consulting company that provides hands-on IT Leadership training, workshops, and coaching.

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