#include <stdio.h>
#include <stdlib.h>
#include <process.h>
#include <conio.h>
#include <ctype.h>
#include <string.h>

void getString(char *str);
int my_strlen(char *str);
int compare(char *source, char *str);

void getFileName(char *str);
void getSearchStr(char *str);
void getReplaceStr(char *str);
void startSearch();
void replaceText();


char *word;
char *filename;
char *search_str;
char *replace_str;
char *tmpname = "chin.XYZ";

FILE *fop, *tpfile;

  void main()
  {
     int count = 0;
     clrscr();

     word = (char *)malloc(sizeof(char) * 20);
     filename = (char *)malloc(sizeof(char) * 20);
     search_str = (char *)malloc(sizeof(char) * 20);
     replace_str = (char *)malloc(sizeof(char) * 20);

     getFileName(filename);
     getSearchStr(search_str);
     getReplaceStr(replace_str);
     startSearch();
/*
     while( feof(fop) == 0)
     {
     fseek(fop,count,0);
     c = getc(fop);
     printf("%c",c);
     count = count + 1L;
     }
 */


     fclose(fop);
     fclose(tpfile);

      if( remove(filename) == 0)
      {
    if (rename( tmpname, filename) == 0)
       printf("Renamed %s to %s.\n", tmpname, filename);
    else
       printf("Cannot renamed. %d", count);
      }

     getch();
  }

  void replaceText()
  {
     int len=0, rplen=0, count=0 ;
     char chr;
     //char *tmpword;char *rplword;
     long i_fptr=0;

     //tmpword = word;
     rplword = replace_str;

     len = my_strlen(word);
     rplen = my_strlen(replace_str);

     fflush(NULL);
     printf("\nMath found. Do you want to replace it 'y' for yes and 'n' for no. : ");
     scanf("%c", &chr);

     if( chr == 'y' || chr == 'Y')
     {
    i_fptr = ftell(tpfile);
    fseek(tpfile,i_fptr - len-1, 0);
    // fseek(fop,i_fptr - len-1, 0);for(count=0; count < rplen; count++)
     {
        putc(*rplword,tpfile);
      // putc(*rplword,fop);
        rplword++;
     }
      putc(' ',tpfile);
      //putc(' ', fop);//fseek(tpfile, i_fptr +( rplen+1-len), 1);
     }

  }

  void startSearch()
  {
     //long count=0;int len=0, count1=0;
     char *tmpword=word;

     tpfile = fopen(tmpname, "w+t");


     while( feof(fop) == 0)
     {
     //fseek(fop,count,0);
     *tmpword = getc(fop);
      putc(*tmpword, tpfile);

     if( isspace(*tmpword) > 0 || *tmpword == '.' || *tmpword == '\n' )
     {
        *tmpword='\0';
        tmpword--;
         if( compare(search_str, word) == 1 )
          {
          //printf("\n match found.");
          replaceText();
          }
           len = my_strlen(word);
           for( count1=0; count1 < len; count1++)
           {    *tmpword=' '; //*tmpword='\0';
            tmpword--;
           }
     }
/*     else if( *tmpword == '\n')
     {
           len = my_strlen(word);
           for( count1=0; count1 < len; count1++)
           {    *tmpword=' '; //*tmpword='\0';
            tmpword--;
           }
     }
*/

     tmpword++;
     //printf("%c",c);//count = count + 1L;
     }

  }

  void getFileName(char *str)
  {
     printf("Enter File name maxium 20 character : ");
     getString(filename);

     if( ( fop = fopen(filename, "r+t") ) == NULL  )
     {  fclose(fop);
    printf("\nInvalid file name entered.");
    getFileName(str);
     }
/*
     if( ferror(fop) != 0)
     { fclose(fop);
       printf("\nSome error has occured. Please enter another file name.");
       getFileName(str);
     }
*/

  }

    void getSearchStr(char *str)
   {
     printf("Enter search string of maxium 20 character : ");
     getString(str);
   }


   void getReplaceStr(char *str)
   {
     printf("Enter replace string of maxium 20 character : ");
     getString(str);
   }

    void getString(char *str)
    {
    int count=0;
    char *getstr;
    char readch='\0';
    fflush(NULL);
       getstr = str;
       while(1)
       {
        scanf("%c", &readch);
        if( readch == '\n')
           break;
        *getstr = readch;

        //if( ( str = (char *)realloc(str, sizeof(char)) ) == '\0')//   break;
        count++;
        getstr++;
        if( count >= 20)
          break;
       }
       *getstr='\0';
    }

   int my_strlen(char *str)
   {
      int _tmpval = 0;
      char *cstr = str;

      if(*cstr != '\0')
      {
     while(*cstr !='\0')
     {
        _tmpval++;
        cstr++;
     }
      }
      return _tmpval;
   }

    int compare(char *source, char *str)
    {
       int cflag = 0;
       char *tsource = source;
        while(1)
        {
          if( *tsource == *str)
        cflag = 1;
          else {
             cflag = 0;
             break;
           }
           tsource++;
           str++;
           if(  *tsource == '\0' || *str=='\0' )
          break;
        }
        return cflag;
    }


     /************************  Input ****************************/


            Content Of Input File text.dat is 

        hello thisis find and replace examples.
        This is only for testing you cannot use this 
        program commerically.


        Enter File name maxium 20 character : text.dat

        Invalid file name entered.Enter File name maxium 20 character : output.txt
        Enter search string of maxium 20 character : this
        Enter replace string of maxium 20 character : there

        Math found. Do you want to replace it 'y'for yes and 'n'for no. : y

        Math found. Do you want to replace it 'y'for yes and 'n'for no. : y

        Math found. Do you want to replace it 'y'for yes and 'n'for no. : y
        Renamed chin.XYZ to output.txt.

     /************************  Output ****************************/


        hello there is find and replace examples.
        This is only for testing you cannot use there
        program commerically.