runidn − A script to allow applications to use internationalized domain names.


runidn [-e local-codeset] program-name [args..]


runidn enables applications to use internationalized domain names without recompilation. Just add ‘‘runidn’’ before the application-name, and the application can handle non-ASCII domain names. For example, you can do:

% runidn telnet non-ASCII-hostname

Before using runidn, you should set up properties related to internationalized DNS by configuring idnkit’s configuration file idn.conf. See idn.conf(5) which describes the configuration.


The following option is available:

Specify the application’s local codeset. If the option is not specified, runidn guesses the codeset from the current locale. See the ‘‘NOTE’’ section for more details about local codeset.


runidn is a small shell script that sets up an environment variable called ‘‘LD_PRELOAD’’, so that an application dynamically links a shared library ‘‘libidnkitres’’ before any other shared libraries.

The library ‘‘libidnkitres’’ provides a special version of resolver functions which implement features for handling internationalized domain names. runidn replaces the following functions with the special version:


By overriding them in the standard libraries with the special version provided by ‘‘libidnkitres’’, runidn enables applications to use internationalized domain names.

These API functions accept non-ASCII domain names encoded in the local codeset that the application is using. Also the result from these APIs may contain non-ASCII domain names.

The normalization and codeset conversion between application’s local codeset and the codeset used in DNS protocol data are handled automatically, so users/applications need not worry about them.

Properties of internationalized DNS (such as the normalization or the codeset used on DNS protocol data) can be configured with the idnkit’s configuration file (idn.conf). See idn.conf(5) for details.


Unless −e option is specified, runidn tries to guess the application’s local codeset from the application’s current locale. However, sometimes it cannot guess the codeset correctly, for example if the application does not set the locale appropriately by calling ‘setlocale()’. In that case, you can explicitly specify the local codeset by setting an environment variable ‘‘IDN_LOCAL_CODESET’’. See the section ‘‘LOCAL CODESET’’ in idn.conf(5) for details.

The idea of using ‘‘LD_PRELOAD’’ to replace some functions in the standard library was taken from ‘‘runsocks’’ script distributed as part of SOCKS5 reference implementation.


There are many cases where runidn does not work.

Your system must support ‘‘LD_PRELOAD’’ mechanism in the first place.

Due to security reasons, ‘‘LD_PRELOAD’’ mechanism is disabled for setuid programs in any sane systems. So runidn does not work for setuid programs such as ping or rsh.

If your application uses a function other than the ones runidn supports for name resolution, you lose.


idn.conf(5), runsocks(1)


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