title: how to print the information in file descriptor in C.
body: <pre><code>(gdb) print* data_out_file[0]
  $1 = {_flags = -1, _IO_read_ptr = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_read_end = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_read_base = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_write_base = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_write_ptr = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_write_end = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_buf_base = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_buf_end = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_save_base = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_backup_base = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, 
    _IO_save_end = 0xffffffffffffffff &lt;Address 0xffffffffffffffff out of bounds&gt;, _markers = 0xffffffffffffffff, _chain = 0x11004147ffffffff, 
    _fileno = 498074112, _flags2 = 12648704, _old_offset = 135392766359363840, _cur_column = 240, _vtable_offset = 66 'B', _shortbuf = "á", 
    _lock = 0xecfc392019202004, _offset = -35, __pad1 = 0xffffffffffffffff, __pad2 = 0xffffffffffffffff, __pad3 = 0xffffffffffffffff, 
    __pad4 = 0xffffffffffffffff, __pad5 = 18446744073709551615, _mode = -1, _unused2 = 'ÿ' &lt;repeats 20 times&gt;}
  </code></pre>
  
  <p>in GDB if we print the file pointer we get the descriptor.
  just wondering how do we do it in C code like printf ?</p>