Popt provides a powerful command-line processing library, allowing the rpm command to handle a variety of options in a very flexible way. You can use popt alone as a library in its own right, or use it combined with the rpm library to handle command-line options like those of the rpm command.

At its most basic, popt processes the command-line arguments to a C program, traditionally called argc and argv, into an option table that describes and contains all the option values.

The main advantage popt has over simpler libraries such as getopt lies in the ability to handle complex arguments and to define aliases. The rpm command supports three different behaviors for the –i option, depending on the context (install a package, get information on a package as part of a query, and perform the install stage of a source RPM, as part of rpmbuild).

The popt library supports both traditional UNIX short options such as –U and the longer options common for GNU programs, especially on Linux, such as --upgrade. For the popt library, you can define both short and long variants for each option. In addition, command-line options may be individual flags, such as –v for verbose, or options that expect one or more data values as arguments, such as –f, which requires a file name.