Hello I am working on a C program that reads a text file and search it for a str

Question

Hello I am working on a C program that reads a text file and search it for a string! I am getting one error that i cannot figure out! Please help!! "Implicit declaration of function 'stringCompare' is invalid in C99"

Please help me work out this bug! My program so far:

#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{
    FILE *fr,*fr1,*fr3;          //declare pointer
    char filename[256];
    char search[256];
    char line[256];
    int count=0;
    char replace[256];
    printf("Enter FileName: "); // ask for filename
    scanf("%s",filename);
    fr3 = fopen (filename, "r");
    if(ferror(fr3)) //check for any error assosicated to file
    {
        fprintf(stderr, "Error in file"); // print error in stderr
        printf("Error");
    }
    printf("Input file data is");
    while(!feof(fr3)) // checking end of file condition
    { //printf("inside");
        fgets(line,256,fr3) ;
      
        printf("%s",line);
      
    }
  
    printf(" Enter String to search: "); //ask for string to search
    scanf("%s",search);
    printf("Enter string with whom you want to replace: "); //ask for string with whom you want to replace one time
    scanf("%s",replace);
    fr = fopen (filename, "r"); // open first file in read mode
    fr1 = fopen ("output.txt", "w"); //open second file in write mode
    if(ferror(fr)) //check for any error assosicated to file
    {
        fprintf(stderr, "Error in file"); // print error in stderr
        printf("Error");
    }
    while(!feof(fr)) // checking end of file condition
    { //printf("inside");
        fgets(line,256,fr) ;
        int r =stringCompare(line,search); // comparing every string and search string
        // printf("%d",r);
        if(r==1 && count==0)
        {
          
            fwrite(replace , 1 , sizeof(replace) , fr1 ); // writing string to file.
            printf("%s ",replace);
            count++;
        }
        else{
            printf("%s",line);
            fwrite(line , 1 , sizeof(line) , fr1 );
        }}
    printf(" ");
    fflush(fr1); // it will flush any unwanted string in stream buffer
    fflush(fr);
    fflush(fr3);
    fclose(fr); //closing file after processing
    fclose(fr1);
    fclose(fr3);
    system("PAUSE");
    return 0;
}
// Compare method which is comparing charaacter by character
int stringCompare(char str1[],char str2[]){
    int i=0,flag=0;
  
    while(str1[i]!='' && str2[i]!=''){
        if(str1[i]!=str2[i]){
            flag=1;
          
            break;
        }
        i++;
    }
  
    if (flag==0 && (str1[i]=='' || str2[i]==''))
        return 1;
    else
        return 0;
  
}

Explanation / Answer

Program:

#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int stringCompare(char str1[],char str2[]){
int i=0,flag=0;
  
while(str1[i]!='' && str2[i]!=''){
if(str1[i]!=str2[i]){
flag=1;
  
break;
}
i++;
}
  
if (flag==0 && (str1[i]=='' || str2[i]==''))
return 1;
else
return 0;
  
}
int main(int argc, char *argv[])
{
FILE *fr,*fr1,*fr3; //declare pointer
char filename[256];
char search[256];
char line[256];
int count=0;
char replace[256];
printf("Enter FileName: "); // ask for filename
scanf("%s",filename);
fr3 = fopen (filename, "r");
if(ferror(fr3)) //check for any error assosicated to file
{
fprintf(stderr, "Error in file"); // print error in stderr
printf("Error");
}
printf("Input file data is");
while(!feof(fr3)) // checking end of file condition
{ //printf("inside");
fgets(line,256,fr3) ;
  
printf("%s",line);
  
}
  
printf(" Enter String to search: "); //ask for string to search
scanf("%s",search);
printf("Enter string with whom you want to replace: "); //ask for string with whom you want to replace one time
scanf("%s",replace);
fr = fopen (filename, "r"); // open first file in read mode
fr1 = fopen ("output.txt", "w"); //open second file in write mode
if(ferror(fr)) //check for any error assosicated to file
{
fprintf(stderr, "Error in file"); // print error in stderr
printf("Error");
}
while(!feof(fr)) // checking end of file condition
{ //printf("inside");
fgets(line,256,fr) ;
int r =stringCompare(line,search); // comparing every string and search string
// printf("%d",r);
if(r==1 && count==0)
{
  
fwrite(replace , 1 , sizeof(replace) , fr1 ); // writing string to file.
printf("%s ",replace);
count++;
}
else{
printf("%s",line);
fwrite(line , 1 , sizeof(line) , fr1 );
}}
printf(" ");
fflush(fr1); // it will flush any unwanted string in stream buffer
fflush(fr);
fflush(fr3);
fclose(fr); //closing file after processing
fclose(fr1);
fclose(fr3);
system("PAUSE");
return 0;
}

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