problems with truncate function

david2008 has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, I have the following code

my $fh = FileHandle->new(">>$log_file") || die "could not open $log_fi
+le: $!";
truncate $fh,0 || die "could not truncate $log_file: $!";
$fh->close() || die "could not close $log_file: $!";
[download]

When running the code i get the error
could not truncate ....: Inappropriate ioctl for device at maintain.pl line 39.

I tried to find the solution with google.
The only restriction i found is that the file has to be opened in append mode (which is our case)
http://perldoc.perl.org/perlport.html#truncate
What are i am doing wrong?

Thanks,
David

Comment on problems with truncate function Download Code

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Re: problems with truncate function by johngg (Canon) on Jun 26, 2013 at 09:29 UTC
What Anonymonk is saying is the `\|\|` has a higher precedence than `or` so either write:- `truncate( $fh, 0 ) \|\| die ...` [download] or `truncate $fh, 0 or die ...` [download] Your code is doing:- `truncate $fh, ( 0 \|\| die ... )` [download] which is not what you want! Cheers, JohnGG	[reply] [d/l] [select]
Re^2: problems with truncate function by david2008 (Scribe) on Jun 26, 2013 at 09:35 UTC
This post made me perl wiser :-). The forum "Seekers of perl wisdom" is really appropriate. Thank you all, David	[reply]
Re: problems with truncate function (perloperator precedence or \|\|) by Anonymous Monk on Jun 26, 2013 at 08:04 UTC
What are i am doing wrong? You're typing "\|\|" when you should be using "or" Common Perl Pitfalls / perltrap , "or die" versus "\|\| die", and two more To \|\| or not to or and why., Perl Idioms Explained - && and \|\| "Short Circuit" operators, \|\| die or or die :)	[reply]
Re^2: problems with truncate function (deparse) by Anonymous Monk on Jun 26, 2013 at 08:09 UTC
Also you're not checking to see how perl views your code with B::Deparse , as recommended by Basic debugging checklist	[reply]
Re^3: problems with truncate function (deparse) by david2008 (Scribe) on Jun 26, 2013 at 09:26 UTC
Hi, You are correct :-) I ran the perl with the B::Deparse module Perl parses the line `truncate $fh,0 \|\| die "could not truncate $dcs_log_file: $!";` [download] to `truncate $fh, die("could not truncate ${log_file}: $!");` [download] Now i also understand the difference between \|\| and or :-) In \|\| it makes 0\|\| before truncate. with or it would make the truncate before Thanks, David	[reply] [d/l] [select]
Re^4: problems with truncate function (deparse) by MidLifeXis (Monsignor) on Jun 26, 2013 at 12:17 UTC
Re: problems with truncate function by tobias_hofer (Friar) on Jun 26, 2013 at 07:59 UTC
I gave a try with a simple file and it works fine. You truncate to 0, means your file will be empty afterwards. if size, 0 in your case, is greater than the files length then the behavior is undefined. Means you got to have some content in your file. Do you have content in your file? See: tuncate Cheers! Tobias	[reply]
Re^2: problems with truncate function by david2008 (Scribe) on Jun 26, 2013 at 09:18 UTC
Hi, My file has content. BR, David	[reply]