#include "stdio.h" 
#include "string.h" 
#include "stdlib.h" 

char* pxEreplace(char *str, char *subStr, char *rep, int num) 
{ 
 char *result = (char *)malloc (sizeof(char *)); 
 int newlen = strlen(rep); 
 int oldlen = strlen(subStr); 
 int i = 0; 

 //replace all instances if value of num less than or equal to 0 
 if (num <= 0) 
 {num = strlen(str);} 

   while (*str) //for the complete input string 
   { 

    if (num != 0 ) // untill no more occurances need to be changed 
    { 
       if (strstr(str, subStr) == str ) 
       { 
          strcpy(&result[i], rep); 
          i += newlen; 
          str += oldlen; 
          num--; 
       } 
       else // if no match is found 
       { 
          result[i++] = *str++; 
       } 
    } 
    else 
    { 
       result[i++] = *str++; 
    } 
   } 

    result[i] = '\0'; //Terminate the string 
     return result; //Return the replaced string 
    free(result);   //free memory