Question

I’m reopening and reading a file, SORTED.txt, after closing it from its first time use – copying all the contents of another file, UNSORTED.txt.
After copying from UNSORTED.txt, I wanted to count the number of lines of what I’ve copied (as a seperate process, and not during the copy process). It seems that fegtc() does not point at the beginning of the file (SORTED.txt) the second time over, hence the value of lines remains as what it was initialized as, 0. Also, in general, can I get the repointing of fgetc() done without closing and reopening the file in consideration?

Grateful for any help.

Cheers!

  f = fopen("./TEXTFILES/UNSORTED.txt", "w");
  if (f == NULL){
      printf("ERROR opening file\n");
      return 100;
  }

  for (i=0; i<1000000; i++){
    fprintf(f, "%d\n", (23*rand()-rand()/13));
  }
  fclose(f);

  f = fopen("./TEXTFILES/UNSORTED.txt", "r");
  if (f == NULL){
    return 100;
  }
  s = fopen("./TEXTFILES/SORTED.txt", "w");
  if (s == NULL){
    return 101;
  }

  while(1){
    j = getc(f);
    if (j == EOF) break;
    fputc(j, s);
  }
  fclose(f);
  //Closed source file. Read number of lines in target file.
  fclose(s);
  s = fopen("./TEXTFILES/SORTED.txt", "w");
  j = 0;

  while(1){
    j = fgetc(s);
    if (j == EOF) break;
    if (j == '\n') lines++;
  }

  fclose(s);
  printf("\n%d\n", lines);

Answer 1

It sounds like you’ve got it figured out! But since I went through the effort of putting this example together, I thought I’d post it anyways.

#include <stdio.h> 

int main()
{
    FILE * f;
    FILE * s;
    int i, j;
    int lines = 0;

    f = fopen("./TEXTFILES/UNSORTED.txt", "w+");
    if (f == NULL){
        printf("ERROR opening file\n");
        return 100;
    }

    for (i=0; i<1000000; i++){
        fprintf(f, "%d\n", (23*rand()-rand()/13));
    }

    s = fopen("./TEXTFILES/SORTED.txt", "w+");
    if (s == NULL){
        fclose(f); // cleanup and close UNSORTED.txt
        return 101;
    }

    // rewind UNSORTED.txt here for reading back
    rewind( f );

    while(1){
        j = getc(f);
        if (j == EOF) break;
        fputc(j, s);
    }

    // done with UNSORTED.txt. Close it.
    fclose(f);

    // rewind SORTED.txt here for reading back
    rewind( s );
    j = 0;

    while(1){
        j = fgetc(s);
        if (j == EOF) break;
        if (j == '\n') lines++;
    }

    fclose(s);

    printf("\n%d\n", lines);

    return 0;
}