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

I was trying out some suggestions for detecting an active dial-up connection with the simplest suggestion to use ipconfig. So I had: 
#!/usr/bin/perl
use warnings;
while(1) {
    open(IPCONFIG,"ipconfig|") or die "can't read from pipe $^E";
    while(<IPCONFIG>) {
        if (/IP Address/) {
            print $_;
        }
    }
sleep(10);
}

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Which works fine on NT 4 but reports warnings under W98. 
C:\Pete>perl connected.pl
        IP Address. . . . . . . . . : 0.0.0.0
Warning: unable to close filehandle IPCONFIG properly.
        IP Address. . . . . . . . . : 0.0.0.0
Warning: unable to close filehandle IPCONFIG properly.
        IP Address. . . . . . . . . : 195.44.21.11

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Both are running ActiveState build 613. If, instead of reading from a pipe I execute the command in backticks and put the result into a scalar the warning does not occur. Can anyone explain what is happening, and if there is anything I can do to prevent the warning.

Replies are listed 'Best First'.
RE: Unable to close filehandle properly
by Odud (Pilgrim) on Jun 14, 2000 at 00:12 UTC
    jcwren suggested "I can't remember if Win98 supports pipes like NT/Unix. I wonder if it's using a temp file, and when the file is empty it's automatically closing it. Perhaps the error is from trying to close an already closed file." So I changed the code to do 
    close(IPCONFIG);
last;

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    after I had recognised the IP Address and the warning message has gone.

    Thanks for that useful advice.
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[d/l]
(jcwren) Re: Unable to close filehandle properly
by jcwren (Prior) on Jun 13, 2000 at 23:30 UTC
    I don't know if it will fix your problem, but I would suggest closing the file at the end of the loop (just prior to the sleep(10)). This would be good programming, in any case.

    --Chris
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      Tried that, it didn't make any difference. I'll play the laziness card here.
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