Name: file_size - get the size of a file

Syntax:
	int file_size(string file)

Description:
	The file_size efun gets the size of a file.

Return value:
	If the file doesn't exist or is not readable by you, -1 is returned.
	If the file is a directory, -2 is returned.
	Else the size of the file in bytes is returned.

Examples:
	int file_size;
	file_size = file_size("/WELCOME");   // could be 1373

See also: efun/save_object, efun/restore_object, efun/write_file, efun/cat, efun/ed, efun/file_date, efun/file_name