Or do you see any serious use cases for it?

Dunno, I think that for random access of small files (say, maybe, under a megabyte) in situations where performance is not critical, the ease of implementation can still outweigh the cost. On the other hand, at least in my experience such files are rare. For example, when inserting lines somewhere, one usually has to scan the file to locate the insertion point anyway, so in such cases a while(<>) loop would still feel more natural to me than a linear search in an array. It's maybe a nice module to show off some of the power (Update: as in expressiveness / TIMTOWTDI, not speed) of Perl to newcomers, although then one might cause the problem of "if all you have is a hammer, everything looks like a nail".

Of course ikegami has a good point. There is a huge difference between reading even a ~1MB file into in array, vs. reading it with Tie::File:

$ cp -L /usr/share/dict/words /tmp/test.txt
$ wc -l /tmp/test.txt
99132 /tmp/test.txt
$ du -sh /tmp/test.txt
920K    /tmp/test.txt

$ time perl -MTie::File -e 'open F, "/tmp/test.txt" or die;
  print `ps -orss $$`; my @x = <F>; print `ps -orss $$`'
  RSS
 7408
  RSS
23604

real    0m0.042s
user    0m0.024s
sys     0m0.012s
$ time perl -MTie::File -e 'tie my @a, "Tie::File", "/tmp/test.txt";
  print `ps -orss $$`; $a=$_ for @a; print `ps -orss $$`'
  RSS
 7612
  RSS
55024

real    0m1.001s
user    0m0.908s
sys     0m0.088s
[download]

Dunno, I think that for random access of small files (say, maybe, under a megabyte) in situations where performance is not critical, the ease of implementation can still outweigh the cost

Except it's just as easy to load the file into memory and write it back out when it's that small.

Except it's just as easy to load the file into memory and write it back out when it's that small.

By "ease of implementation" I meant:

open my $ifh, '<', $file or die $!;
chomp( my @a = <$ifh> );
close $ifh;                      # vs.
                                       use Tie::File;
                                       tie my @a, 'Tie::File', $file;
# and

open my $ofh, '>', $file or die $!;
print $ofh $_,"\n" for @a;
close $ofh;                      # vs.
                                       untie @a;
[download]

I think several arguments, some subjective, could be made in either direction which one "easier". Whether it's worth the cost (speed and memory penalty) depends on the application, and of course the user must be aware of the penalty in the first place, so it's definitely good to caution. I just personally wouldn't reject the module outright.

Granted, if it's about reducing the length of the code, it's also possible to do something like this, although it still has a speed penalty, just not quite as bad as Tie::File:

use Path::Class qw/file/;
my @a = file($file)->slurp(chomp=>1);
...
file($file)->spew_lines(\@a);
[download]

A while(<>) should still be faster than any of the above. (I ran some quick back-of-the-envelope benchmarks with /usr/share/dict/words.)

Karl asked about "serious" use cases. Under the conditions I named, I'd say it's just a matter of TIMTOWTDI, but if you were to say that's not a "serious" use case, then you wouldn't be wrong. I think I'll be cautioning against Tie::File more in the future.

Thank you very much for advice haukex. But to be honest: I struggle a bit about what you benchmarked. I guess i need to take a closer look at your results ;-) Best regards, Karl

«The Crux of the Biscuit is the Apostrophe»

perl -MCrypt::CBC -E 'say Crypt::CBC->new(-key=>'kgb',-cipher=>"Blowfish")->decrypt_hex($ENV{KARL});'Help

Didnt you look at the benchmark?

Or do you see any serious use cases for it?

I do not. Let's revisit my first words on this: "First of all, you don't want Tie::File. You never want Tie::File."

Thank you very much for advice ikegami. Best regards, Karl

«The Crux of the Biscuit is the Apostrophe»

perl -MCrypt::CBC -E 'say Crypt::CBC->new(-key=>'kgb',-cipher=>"Blowfish")->decrypt_hex($ENV{KARL});'Help