This program generates a C function that uses getopt_long function
to parse the command line options, to validate them and fills a
struct .

Thus your program can now handle options such as:

myprog --input foo.c -o foo.o --no-tabs -i 100 *.class

And both long options (those that start with --) and short options
(start with - and consist of only one character) can be handled.

Gengetopt can also generate a function to save the command line
options into a file, and a function to read the command line options
from a file. Of course, these two kinds of files are compliant.