Parsing Long Options

Find this topic in DOCUMENT of GNU C library: libc

http://www.gnu.org/software/libc/manual/   From page 633

Here I conclude some useful tips:

== return values of getopt():

• successful
• a character (the option name without argument)
• a character (the option name), a pointer to char (char *optarg: argument)
• failed
• '?' (not included in options OR missing argument) (int optopt keeps the character)
• -1 complete

== return values of getopt_long ():

• successful
• short_options
• (same with getopt())
• long_options
• content of val (flag = NULL) (Tips, put corresponding short option char in val)
• 0 (flag != NULL, put content of val into *flag)
• (same with above two) (with argument are stored in optarg)
• failed
• (same with getopt())
• -1 complete

    PS: indexptr record the index of the options in array of struct option.