#define _GNU_SOURCE #include <getopt.h> int getopt_long_only(int argc, char * const argv, const char *optstring, const struct option *longopts, int *longindex);
getopt_long_only() is like getopt_long(), but - as well as -- can indicate a long option. If an option that starts with - (not --) doesn't match a long option, but does match a short option, it is parsed as a short option instead.
The function getopt_long_only() returns the option character if the option was found successfully, : if there was a missing parameter for one of the options, ? for an unknown option character, or -1 for the end of the option list. getopt_long_only() also returns the option character when a short option is recognized. For a long option, they return val if flag is NULL, and 0 otherwise. Error and -1 returns are the same as for getopt(), plus ? for an ambiguous match or an extraneous parameter.