#include <stdio.h>
#include <string.h>
#include <stdlib.h>

// substring.c
// compile with: gcc -o substring substring.c
// run with:     ./substring "input string" start_index end_index

int main(int argc, char **argv) {
 // argv[1] is the inputted string	// first argument

 // atoi(); is a function that converts strings to integers;	refer to `man 3 atoi'
 int start	= atoi(argv[2]);	// second argument;	start position
 int end	= atoi(argv[3]);	// third argument;	end position

 // allocate space for our inputted string.
 char *string	= malloc(sizeof(char) * (strlen(argv[1]) + 1));

 // copy input string to working string
 strcpy(string,argv[1]);

 // allocate space for our partial string
 char *str	= malloc(sizeof(char) * end);

 // the magic
 strncpy(str,&(string[start]),end);

 // and the goods.
 printf("input string = \"%s\"; start: %d; end: %d; returned string = \"%s\";\n",argv[1],start,end,str);

 return EXIT_SUCCESS;
}