Normally programs using argp need not be written with particular
printing argument-usage-type help messages in mind as the standard
`--help' option is handled automatically by argp. Typical error
cases can be handled using
argp_error. See Argp Helper Functions. However, if it's
desirable to print a help message in some context other than parsing the
program options, argp offers the
This outputs a help message for the argp parser argp to stream. The type of messages printed will be determined by flags.
Any options such as `--help' that are implemented automatically by argp itself will not be present in the help output; for this reason it is best to use
argp_state_helpif calling from within an argp parser function. See Argp Helper Functions.