Getting filename from IO::File object

arunhorne has asked for the wisdom of the Perl Monks concerning the following question:

I am subclassing the Graph::Writer module to provide output for a new graph format and must work within the confines of the following function.

sub _write_graph
{
    my $self  = shift;
    my $graph = shift;
    my $FILE  = shift;

    #while (<$FILE>)
    #{
    #}
    
    return 1;
}
[download]

The function receives a file handle (IO::File=GLOB(0x8333a68)) to a single file ($FILE). However, I need to create two output files for this graph format and thus I need to get the filename from the $FILE file handle and use this as the base name from which I can generate two new filenames and open these for output (and close $FILE). I know this is a bit of a kludge, but I'm within the confines of original function that is being overriden. How can I do this, or has anyone got a better idea how I could do it without changing the parameters accepted by the function?

Note that I need concurrent access to the two new files rather than sequential so will need two open file handles at once.

Thanks, Arun

____________
Arun

Comment on Getting filename from IO::File object Select or Download Code

Replies are listed 'Best First'.
Re: Getting filename from IO::File object by Jaap (Curate) on Jan 30, 2003 at 12:22 UTC
To my knowledge, the IO::File module has no method for retrieving the filename of a IO::File object, so no luck there. Then you have to think about how to extend the _write_graph object with backwards compatibility. I suggest adding an optional parameter. When this parameter is not set, just use the original code. If it is set, switch to your new code (which can then use the new parameter).	[reply]
•Re: Getting filename from IO::File object by merlyn (Sage) on Jan 30, 2003 at 15:45 UTC
There may not even be a filename for the IO::File object. For example: `my $handle = IO::File->open("/tmp/my$$", "w+"); unlink "/tmp/my$$";` [download] This handle functions completely nicely (at least in Unix), but has no "name". When the last reference to this handle is closed, the disk space in `/tmp` is reclaimed. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: Getting filename from IO::File object by derby (Abbot) on Jan 30, 2003 at 13:45 UTC
I don't know much about Graph::Writer, but getting a filename from a filehandle (or filedescriptor) is quite a thorny issue that cannot be solved in a platform independent way. If Graph::Writer supplies methods for opening files, your best bet is to also subclass that method and store the filename in the object. -derby	[reply]