Thread: counting duplicates from one file to another not correct on larger files

The program takes two txt files as arguments, the text file to be searched and the the text file containing the string to search for. We aren't allowed to use any string library functions. For some reason it works just fine on smaller text files for example:

textFileToSearch.txt:

this is fun
is this fun
fish

patternToSearchFor.txt:

is

returns:

Matches: 5

which is correct.

but if I use a much larger file like this:

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and search for

er

, it returns:

Matches: 62

when I'm pretty sure there are only 18 "er"s in that file.

I can't figure out why it doesn't work on bigger files. Any help would much appreciate.

(I know the Lines and Columns part isn't correct either, I'm more worried about the counting part right now)

Code:

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

int patternFileLength(FILE *pattern){
  int len = 0;
  int chr;

  while((chr = fgetc(pattern)) != EOF){
    if(chr != '\0'){
      len++;
    }
  }
  return len;
}

int charcmp( char a, char b, int type ){
  if ( a == b ){
    type = 1;
    return 1;
  }
  else if(a == b || a - 32 == b || a + 32 == b){
    type = 2;
    return 1;
  }
  else if((a >= 48 && a <= 57) && (b >= 48 && b <= 57)){
    type = 3;
    return 1;
  }
  else{
    return 0;
  }
}

int main(int argc, char *argv[])
{
  FILE *textFile;
  FILE *patternFile;
  char x,y;
  int type = 0, match = 0, count = 0;
  int line = 1, col = -3;

  textFile = fopen(argv[1], "r");
  patternFile = fopen(argv[2], "r");

  int length = patternFileLength(patternFile);
  rewind(patternFile);

  y = fgetc(patternFile);

  while((x = fgetc(textFile)) != EOF){
    if(charcmp(x, y, type) == 1){
      y = fgetc(patternFile);
      match++;
      if(match == length){
        count++;
        match = 0;
        printf("LINE: %d    COL: %d\n", line, col);
      }
    }
    else{
      rewind(patternFile);
      y = fgetc(patternFile);
    }
    if(x == '\n' || x == '\0'){
      line++;
      col = -3;
    }
    col++;
  }

  printf("\nMatches: %d\n", count);

  fclose(textFile);
  fclose(patternFile);

  return 0;
}

Ah, I see the problem with the second if statement now, thank you. That doesn't really solve the problem with getting so many extra matches with the current files I'm using because none of them contain anything except letters and they wouldn't be picking up any punctuation with what I'm search for, I think? The third if statement is part of the assignment, we are supposed to make numbers match with other numbers. The type parameter in the charcmp is also a requirement in the homework that just hasn't been put to use yet.

I'm not sure how I'd put the files into strings and operate on the strings when we aren't allowed to use string library functions?

To read a file into a string:
1. determine the filesize - write a function long file_size(const char *filename)
2. allocate a buffer with malloc - using the length of the file
3. read the file with fread into the buffer
4. close the file

If you can't use the string library functions you need to write your own.
You basically need a strstr function.

Hope this makes sense. English is not my native language so it might sound a bit clumsy.