FileCache Usage

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

Dear Monks,

I assume I am being dopey, but I don't understand why this

  my $fh;
  open($fh,'<',$file);
  while (<$fh>) {
    print "line: $_\n";
  }
[download]

is OK, whereas this

  my $fh;
  $fh = cacheout('<',$file);
  while (<$fh>) {
    print "line: $_\n";
  }
[download]

tells me

readline() on unopened filehandle 1 at ...
readline() on unopened filehandle 2 at ...
readline() on unopened filehandle 3 at ...
...
[download]

Can someone please enlighten me?

Update: I'm using Perl 5.8.0 on solaris.

Thanks,

loris

"It took Loris ten minutes to eat a satsuma . . . twenty minutes to get from one end of his branch to the other . . . and an hour to scratch his bottom. But Slow Loris didn't care. He had a secret . . ." (from "Slow Loris" by Alexis Deacon)

Comment on FileCache Usage Select or Download Code

Replies are listed 'Best First'.
Re: FileCache Usage by Corion (Patriarch) on Feb 09, 2007 at 09:48 UTC
Most likely because `cacheout`, whatever that is, returns `undef` instead an opened filehandle. Check that: `die "Didn't get a sensible result from cacheout() for '$file'. Maybe t +his helps: $!" unless $fh;` [download] Looking closer at your error message and the increasing number of filehandles, it seems that `cacheout()` returns a fileno and not something that Perl considers a valid, open filehandle. The error is likely in `cacheout()`. Looking closer at your topic I now realize you're talking about FileCache, stupid me. Looking even closer, I can't replicate your problem: `Q:\>type test.txt 1 2 3 Q:\>perl -MFileCache -le "my $fh = cacheout('<','test.txt'); print for + <$fh>" 1 2 3 Q:\>perl -MFileCache -le "my $fh = cacheout('<','does-not-exist.txt'); + print for <$fh>" Can't create does-not-exist.txt: No such file or directory at -e line +1` [download] So maybe the file exists but you don't have read permissions? This is on Win32, Perl 5.8.2, stock FileCache	[reply] [d/l] [select]
Re^2: FileCache Usage by loris (Hermit) on Feb 09, 2007 at 10:05 UTC
The file does exist and is readable. Otherwise the `open` version wouldn't work either, would it? Thanks, loris "It took Loris ten minutes to eat a satsuma . . . twenty minutes to get from one end of his branch to the other . . . and an hour to scratch his bottom. But Slow Loris didn't care. He had a secret . . ." (from "Slow Loris" by Alexis Deacon)	[reply] [d/l]
Re: FileCache Usage by PreferredUserName (Pilgrim) on Feb 09, 2007 at 16:13 UTC
You should always say: "`open(...) or die $!`", or in your case "`cacheout(...) or die $!`". You can't just assume that open() worked, as it frequently does not.	[reply] [d/l] [select]