./a.out thisisatest 0 8
substring = "thisisat"

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

char *substring(size_t start, size_t stop, const char *src, char *dst,
        size_t size)
{
    unsigned int count = stop - start;
    if (count >= --size) {
    count = size;
    }
    sprintf(dst, "%.*s", count, src + start);
    return dst;
}

int main(int argc, char **argv)
{

    char *text; //Line 40, change to text[100] will work
    char *a;    //Line 41, change to a[100] will work
    int start, end;

    if (argc != 4) {
    printf("Error! Usage:\n\t \
argv[0]=program;\n\t \
argv[1]=input string\n\t \
argv[2]=start_position of string\n\t \
argv[3]=end_postion of string\n");

    return 1;
    }

    strcpy(text, argv[1]);
    start = atoi(argv[2]);
    end = atoi(argv[3]);

    printf("substring = \"%s\"\n",
       substring(start, end, text, a, sizeof(a)));

    return 0;
}