struct optio結構體的定義

標頭檔案

extern char *optarg;
extern int optind, opterr, optopt;

#include <getopt.h>

int getopt_long(int argc, char * const argv[],
                const char *optstring,
                const struct option *longopts, int *longindex);

結構體

struct option {
    const char *name;
    int
 
 has_arg;
    int *flag;
    int val;
};

描述

 longopts is a pointer to the  first  element  of  an  array  of
       struct option declared in <getopt.h> as

           struct option {
               const char *name;
               int         has_arg;
               int        *flag;
               int         val;
           };

       The meanings of
 
 the different fields are:

       name   is the name of the long option.

       has_arg
              is:  no_argument  (or  0) if the option does not take an
              argument;  required_argument  (or  1)  if   the   option
              requires an argument; or optional_argument (or 2) if the
 

              option takes an optional argument.

       flag   specifies how results are returned for  a  long  option.
              If  flag  is NULL, then getopt_long() returns val.  (For
              example, the calling program may set val to the  equiva-
              lent  short option character.)  Otherwise, getopt_long()
              returns 0, and flag points to a variable which is set to
              val  if  the  option is found, but left unchanged if the
              option is not found.

       val    is the value to return, or to  load  into  the  variable
              pointed to by flag.

       The last element of the array has to be filled with zeros.

       If  longindex is not NULL, it points to a variable which is set
       to the index of the long option relative to longopts.

has_arg