How it works...

This recipe attempts to demonstrate most of the common usages of the flag package. It shows custom variable types, a variety of built-in variables, shorthand flags, and writing all flags to a common struct. This is the first recipe to require a main function, as the main usage of flag (flag.Parse()) should be called from main. As a result, the normal example directory is omitted.

The example usage of this application shows that you get -h automatically to get a list of flags that are included. Some other things to note are Boolean flags that are invoked without arguments, and the flag order doesn't matter.

The flag package is a quick way to structure input for command-line applications and provide a flexible means of specifying upfront user input for things such as setting up log levels or verbosity of an application. In the command-line arguments recipe, we'll explore flag sets and switch between them using arguments.