C Programming (getopt)

Take a look at The GNU documentation on getopt.
Bring up a terminal and view the manpage for getopt (man 3 getopt).

GETOPT(3) Linux Programmer's Manual GETOPT(3) NAME getopt, getopt_long, getopt_long_only, optarg, optind, opterr, optopt - Parse command-line options SYNOPSIS #include <unistd.h> int getopt(int argc, char * const argv[], const char *optstring); extern char *optarg; extern int optind, opterr, optopt;

getopt is repeatedly called to get the next command line option
optstring is a string indicating the options we are interested in, a colon (:) after an option indicates that this option is associated with an argument
optind is the current index into argv
optarg is a pointer to this options argument, if the option has an argument
optopt is the currently scanned option

Work in pairs to understand the following examples and then complete the associated exercise.

Exercise

Complete getoptExercise.c which behaves as follows: it prints the sum of the -x and -y arguments. If the -d option is present, it doubles the sum. For example: apps0> gcc -o getoptExercise -Wall getoptExercise.c apps0> ./getoptExercise -x 12 12 apps0> ./getoptExercise -x 12 -d 24 apps0> ./getoptExercise -x -d Option -x requires an integer argument. apps0> ./getoptExercise -y 10 -d -x 12 44 apps0> ./getoptExercise -x 10 -y 12 -d 44 apps0> ./getoptExercise -x 10 -y 12 22