getopt_long is useful to work with the command line arguments. But while working with getopt_long, – is used for long options and – for short options. getopt_long_only accepts both — and – for long options

- rectangle -a -l 12 -b 34: will calculate the area of the rectangle
- square -p -l 12 -b 34: will calculate the perimeter of the rectangle
- rectangle -a -p -l 12 -b 34: will calculate the area and perimeter of the rectangle
- rectangle –area –length 12 –breadth 34: will calculate the area of the rectangle
- square -perimeter –length 12 –breadth 34: will calculate the perimeter of the rectangle
- rectangle -area -perimeter –length 12 –breadth 34: will calculate the area and perimeter of the rectangle

The program is much like getopt_long.

#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <getopt.h> /** Program to calculate the area and perimeter of * a rectangle using command line arguments */ void print_usage() { printf("Usage: rectangle [ap] -l num -b num\n"); } int main(int argc, char *argv[]) { int opt= 0; int area = -1, perimeter = -1, breadth = -1, length =-1; //Specifying the expected options //The two options l and b expect numbers as argument static struct option long_options[] = { {"area", no_argument, 0, 'a' }, {"perimeter", no_argument, 0, 'p' }, {"length", required_argument, 0, 'l' }, {"breadth", required_argument, 0, 'b' }, {0, 0, 0, 0 } }; int long_index =0; while ((opt = getopt_long_only(argc, argv,"", long_options, &long_index )) != -1) { switch (opt) { case 'a' : area = 0; break; case 'p' : perimeter = 0; break; case 'l' : length = atoi(optarg); break; case 'b' : breadth = atoi(optarg); break; default: print_usage(); exit(EXIT_FAILURE); } } if (length == -1 || breadth ==-1) { print_usage(); exit(EXIT_FAILURE); } // Calculate the area if (area == 0) { area = length * breadth; printf("Area: %d\n",area); } // Calculate the perimeter if (perimeter == 0) { perimeter = 2 * (length + breadth); printf("Perimeter: %d\n",perimeter); } return 0; }