Auto-complete command line arguments

Question

In bash, executables such as mplayer and imagemagick\'s \"convert\" have a cool auto-complete functionality on their command line arguments. For instance, if I type

Answer 1

This functionality in bash is provided by bash-completion and similar functionality is included in zsh. If you want to add support for some program not currently supported by one of these tools, you need to write your own extensions for them.