C Substring

/*
Write a program in C for Substring
*/
 
#include<stdio.h>
#include<malloc.h>

char* substring(char*, int, int);

main()
{
char string[100], *pointer;
int position, length;

printf("Enter a string\n");
gets(string);

printf("Enter the position and length of substring\n");
scanf("%d%d",&position, &length);

pointer = substring( string, position, length);

printf("Required substring is \"%s\"\n", pointer);

free(pointer);

return 0;
}

/*C substring function: It returns a pointer to the substring */

char *substring(char *string, int position, int length)
{
char *pointer;
int c;

pointer = malloc(length+1);

if( pointer == NULL )
{
printf("Unable to allocate memory.\n");
exit(EXIT_FAILURE);
}

for( c = 0 ; c < position -1 ; c++ )
string++;

for( c = 0 ; c < length ; c++ )
{
*(pointer+c) = *string;
string++;
}

*(pointer+c) = '\0';

return pointer;
}