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

Tags: filesize io file c

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

#include <stdio.h>

unsigned int fsize(char* file){
  //what goes here?
By : andrewrk


If you're fine with using the std c library:

#include <sys/stat.h>
off_t fsize(char *file) {
    struct stat filestat;
    if (stat(file, &filestat) == 0) {
        return filestat.st_size;
    return 0;
By : NilObject

Here's a simple clean function that return the file size

long get_file_size(char *path)
    FILE *fp;
    /* Open file for reading */
    fp = fopen(path, "r");
    fseek(fp, 0, SEEK_END);
    return ftell(fp); 

**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) ){
      return -1;

    size = ftell(fh);
    return size;

  return -1; //error
By : andrewrk

This video can help you solving your question :)
By: admin