请教getopt(),getopt_long()中的optind

kggg

The variable optind is the index of the next element to be processed in argv.  The system initializes this
       value to 1.  The caller can reset it to 1 to restart scanning of the same argv, or  when  scanning  a  new
       argument vector.

       If  getopt()  finds  another  option  character, it returns that character, updating the external variable
       optind and a static variable nextchar so that the next call to getopt() can resume the scan with the  fol-
       lowing option character or argv-element.

       If  there  are  no  more  option characters, getopt() returns -1.  Then optind is the index in argv of the
       first argv-element that is not an option.

指向argv下一个元素的索引， 这指的是什么啊
试过printf optind, 可是有参数的得到3，没参数的是2.

ubuntuer

./getopt --add a  --delete d
optind:       1          2   3      4        5