These variables make it easy for user programs to implement the `--version' option and provide a bug-reporting address in the `--help' output. These are implemented in argp by default.
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_EXITflag is used.
If defined or set by the user program to a non-zero value,
argp_program_bug_addressshould 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.'.
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_HELPflag is used. If the
ARGP_NO_EXITflag 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.