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

int main(void) {
	int start_index = 1;
	int loop_count = 6;
	char inputline[] = "This is my day in 2020 1230023";
	char substr[1024];
	
    strncpy ( substr, inputline + start_index, loop_count);
    substr[loop_count] = '\0';
    printf("%s\n", substr); //  you can use fprintf(outfile, "%s", substr); here
	return 0;
}