Comments on: use autodie; http://blog.bluefeet.net/2009/06/use-autodie/ Yet another Perl Hacker weblog Wed, 23 Jun 2010 03:52:38 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: racer http://blog.bluefeet.net/2009/06/use-autodie/comment-page-1/#comment-62 racer Mon, 20 Jul 2009 10:43:02 +0000 http://blog.bluefeet.net/?p=80#comment-62 Chas.Owens, you forgot <code> do </code> after that <code> or </code> :) unlink('testfile.txt') if -e 'testfile.txt'; is a race condition, testfile.txt could exist when -e 'testfile.txt'; is called, but be deleted before unlink is called. Not to worry, since autodie and $fh are lexically scoped, you could simply write <code> use autodie; eval { open( my $fh, '<', 'testfile.txt' ); print $fh "Hello world!\n"; 1; } or do { no autodie 'unlink'; unlink 'testfile.txt'; die; }; </code> or <code> my $file = q'testfile.txt'; eval { use autodie; open( my $fh, '<', $file ); print $fh "Hello world!\n"; 1; } or do { unlink $file; die }; </code> Chas.Owens, you forgot

 do

after that

 or

:)

unlink(‘testfile.txt’) if -e ‘testfile.txt’; is a race condition, testfile.txt could exist when -e ‘testfile.txt’; is called, but be deleted before unlink is called.

Not to worry, since autodie and $fh are lexically scoped, you could simply write

    use autodie;
    eval {
        open( my $fh, '<', 'testfile.txt' );
        print $fh "Hello world!\n";
        1;
    } or do {
        no autodie 'unlink';
        unlink 'testfile.txt';
        die;
    };

or

    my $file = q'testfile.txt';
    eval {
        use autodie;
        open( my $fh, '<', $file );
        print $fh "Hello world!\n";
        1;
    } or do {
        unlink $file;
        die
    };
]]> By: Chas. Owens http://blog.bluefeet.net/2009/06/use-autodie/comment-page-1/#comment-9 Chas. Owens Tue, 30 Jun 2009 15:39:20 +0000 http://blog.bluefeet.net/?p=80#comment-9 Your eval version can be a little cleaner: my $file = "testfile.txt"; eval { open my $fh, ">", $file; print {$fh} "Hello world!\n"; close $fh; } or { warn $@; unlink $file if -e $file; exit 255; } Since close will return true if it succeeds, we can use that return to build a try/catch like system that is not dependent on $@ (which could be changed by an errant DESTROY method that failed to localize it). Also, warning about the error means that if the unlink fails it won't mask the error from the eval. Your eval version can be a little cleaner:

my $file = “testfile.txt”;
eval {
open my $fh, “>”, $file;
print {$fh} “Hello world!\n”;
close $fh;
} or {
warn $@;
unlink $file if -e $file;
exit 255;
}

Since close will return true if it succeeds, we can use that return to build a try/catch like system that is not dependent on $@ (which could be changed by an errant DESTROY method that failed to localize it). Also, warning about the error means that if the unlink fails it won’t mask the error from the eval.

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