How do you determine the size of a file in C?

Question

How can I figure out the size of a file, in bytes?

#include 

unsigned int fsize(char* file){
  //what goes here?
}

Answer 1

**Don't do this (why?):

Quoting the C99 standard doc that i found online: "Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has undefined behavior for a binary stream (because of possible trailing null characters) or for any stream with state-dependent encoding that does not assuredly end in the initial shift state.**

Change the definition to int so that error messages can be transmitted, and then use fseek() and ftell() to determine the file size.

int fsize(char* file) {
  int size;
  FILE* fh;

  fh = fopen(file, "rb"); //binary mode
  if(fh != NULL){
    if( fseek(fh, 0, SEEK_END) ){
      fclose(fh);
      return -1;
    }

    size = ftell(fh);
    fclose(fh);
    return size;
  }

  return -1; //error
}