— Variable: const char * argp_program_version

If defined or set by the user program to a non-zero value, then a ‘--version’ option is added when parsing with argp_parse, which will print the ‘--version’ string followed by a newline and exit. The exception to this is if the ARGP_NO_EXIT flag is used.

— Variable: const char * argp_program_bug_address

If defined or set by the user program to a non-zero value, argp_program_bug_address should point to a string that will be printed at the end of the standard output for the ‘--help’ option, embedded in a sentence that says ‘Report bugs to address.’.

— Variable: argp_program_version_hook

If defined or set by the user program to a non-zero value, a ‘--version’ option is added when parsing with arg_parse, which prints the program version and exits with a status of zero. This is not the case if the ARGP_NO_HELP flag is used. If the ARGP_NO_EXIT flag is set, the exit behavior of the program is suppressed or modified, as when the argp parser is going to be used by other programs.

It should point to a function with this type of signature:

          void print-version (FILE *stream, struct argp_state *state)

See Argp Parsing State, for an explanation of state.

This variable takes precedence over argp_program_version, and is useful if a program has version information not easily expressed in a simple string.

— Variable: error_t argp_err_exit_status

This is the exit status used when argp exits due to a parsing error. If not defined or set by the user program, this defaults to: EX_USAGE from <sysexits.h>.