[Kde-perl] listview and filehandles

toiletpaper usedtoiletpaper at thecookies.org
Mon Apr 26 11:37:52 CEST 2004

toiletpaper wrote:

> Rich wrote:
>>On Sunday 25 Apr 2004 2:50 am, Edward wrote:
>>>ok well. heres something really odd. when using the listView in perlqt i
>>>can no longer close or write to filehandles. they supposedly open fine
>>>but when i print to them nothing prints and when i close them using
>>>close FHA or die "cant close $pathname: $!";
>>>i get cant close /tmp/Adema.Adema: Bad file descriptor at
>>>/root/ui/form1.pl line 234
>>>    #    $pathname = "/tmp/Adema.Adema";
>>>    #    print "Opening file and printing to it\n";
>>>    #    open(FHA, "> $pathname")    or die "can't open $pathname: $!";
>>>    #    #flock(FH, LOCK_EX)        or die "can't flock $pathname: $!";
>>>    #    print FHA "hello there\n"     or die "cant print $pathname: $!";
>>>    #    close(FHA)            or die "cant close $pathname: $!";
>>This isn't going to answer your question, but a couple of suggestions:
>>1) Use a lexical scalar for filehandles.
>>On modern(ish) perls you can do the following:
>>open my $fh, ">", $pathname  or die "can't open $pathname: $!";   #<<<<
>>print $fh "hello there\n"     or die "cant print $pathname: $!";
>>close $fh                        or die "cant close $pathname: $!";
>>This is generally a good thing, as it both limits filehandle scope, and closes 
>>files when the handle goes out of scope, ie:
>>  open my $fh, ">", $pathname  or die "can't open $pathname: $!";   #<<<<
>>  print $fh "hello there\n"     or die "cant print $pathname: $!";
>>}  ## File closes here as $fh goes out of scope.
>>Its still a good idea to explicitly close files as soon as they're not needed 
>>however. You never know, that might solve your problem (but probably not).
>>Also note the three argument form of open is safer than the two argument form. 
>>perldoc -f open for lots of details (BTW the perlopentut docs for my version 
>>(5.8.0) seem pretty out of date as the examples dont use lexical scalars for 
>>2) $pathname = "/tmp/Adema.Adema";
>>Do you want a temporary file here? If so, you *must* use File::Temp - read the 
>>docs for the reasons why.
>>If you actually want to store data between runs, don't put the file in /tmp - 
>>this is for temporary files, and there's no guarantee when data in /tmp will 
>>be deleted. 
>>Instead you could use File::HomeDir to find a suitable directory, then create 
>>a hidden subdirectory and store data there - this will work on Unix style 
>>systems, for windows there would be better alternatives but I'm not in a 
>>position to comment.
>>3) If you're going to add file locking, make sure you read the docs in detail 
>>- there are some subtleties that make it easy to get wrong.
>>Sorry this doesn't answer your question, but it will make the code slightly 
>>more robust!
> well, i changed it to the lexical scalars as you suggested.
> i had it put the file in the /tmp folder because it was just to see if 
> it was working. so i changed it to the /home directory. same results. 
> nothing prints and cant close it saying:
> cant close /home/Adema.Adema: Bad file descriptor at ./form1.pl line 225.
> i decided file locking was pretty much a waste as only one program is 
> going to write this file at a time, no need to prevent others from 
> writing to it as well.
> i dont really think its something to do with the 
> opening/printing/closing code in the end because when it is placed 
> before the listview line it works fine. i am going to try using the 
> kde listview control tommorow instead of the generic listview. with 
> some luck it will work the way its supposed to.
> the new subroutine looks like this:
> sub puttrackinfo_tofile {
>     my $pathname = "/home/Adema.Adema";
>     my $line;
>     my $dontadd = FALSE;
>     my $lookforme;
>     my $counter;
>     $lookforme = join($combochars, $artist, $album, $tracknumber, 
> $trackname, $tracklength, $genre);
>     #open(my $ALBUMINFO,"<", $pathname);
>     #my @rawdata = <$ALBUMINFO>;
>     #close $ALBUMINFO;
>     print "filepath=$pathname\n";
>     print "filelinecount=$#rawdata\n";
>     if (!$#rawdata == -1) {
>         foreach $line (@rawdata) {
>             if ("$line" eq "$lookforme") {  
>                 $dontadd=TRUE;
>             }
>             print $line,"\n";
>         }
>     }
>     #if ($dontadd == FALSE) {
>         print "Opening file and printing to it\n";
>         open my $FHA, ">>", $pathname    or die "can't open $pathname: 
> $!";
>         print $FHA "$lookforme\n"     or die "cant print $pathname: $!";
>         close $FHA            or die "cant close $pathname: $!";
>     #}
> }

ok well. i decided to spend a little time and try that klistview, its 
the same control, i wonder why the qt-designer says they are different, 
i looked at the code and they were the same thing just missing the 
trUtf8 in the title part of the code. but same results :( any help would 
be greatly appreciated
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