How to print File pointer

[padma31]

Hi

I have a file pointer which is pointing to a file in the physical disk. Now I wanted to know which file it is pointing to. Is there a way to print it using file pointer.

Regards
Padma

[RRick]

The simplest way is to get the program in the debugger and look at the file pointer.

GNU will let you see the values, but I doubt it will help you. For the following program

#include <stdio.h>
 
int main( void)
{
    FILE * file = fopen( "t.c", "r");
 
    printf ( "FILE: %p\n", file);
}

When stopped at line 7, the debugger says:

(gdb) p *file
$3 = {
  _flags = -72539000, 
  _IO_read_ptr = 0x0, 
  _IO_read_end = 0x0, 
  _IO_read_base = 0x0, 
  _IO_write_base = 0x0, 
  _IO_write_ptr = 0x0, 
  _IO_write_end = 0x0, 
  _IO_buf_base = 0x0, 
  _IO_buf_end = 0x0, 
  _IO_save_base = 0x0, 
  _IO_backup_base = 0x0, 
  _IO_save_end = 0x0, 
  _markers = 0x0, 
  _chain = 0x70d480, 
  _fileno = 7, 
  _flags2 = 0, 
  _old_offset = 0, 
  _cur_column = 0, 
  _vtable_offset = 0 '\0', 
  _shortbuf =     "", 
  _lock = 0x8ae40a0, 
  _offset = -1, 
  __pad1 = 0x0, 
  __pad2 = 0x8ae40ac, 
  _mode = 0, 
  _unused2 =     '\0' <repeats 51 times>
}
 

I don't see a lot of useful information here.

[Banfa]

I have a file pointer which is pointing to a file in the physical disk. Now I wanted to know which file it is pointing to. Is there a way to print it using file pointer.

Yes store the name of the file that you opened when you open it.

[Banfa]

I don't see a lot of useful information here.

Not to mention that that information would be platform dependent and not guaranteed to be the same on all systems (although it probably would be the same on all systems running the same OS on the same hardware).