how to make c know the size of a file code example

Example 1: c get file size

FILE *fp = fopen("example.txt", "r");
fseek(fp, 0L, SEEK_END);
int size = ftell(fp);

Example 2: c file size

If you use :

/** 
	Pay attention to return type! 
	ftell returns long, which can only be used for files under 2GB. 
**/
fseek(f, 0, SEEK_END); // seek to end of file
size = ftell(f); // get current file pointer
fseek(f, 0, SEEK_SET); // seek back to beginning of file

// If u want to get file of large size, use stat() instead
struct stat buf;
if(stat(filename, &buf) == -1){
   return -1;
}
return (ssize_t)buf.st_size;