simple to describe I/O problem

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

I just can not open some files I received.

When this simple chunk of code is executed

use IO::File;
my @data;
if (-e $file) { print "\nopen $file\n"; }

if (my $fh->open("$file, r")) {
print "I'm in\n";
@data = <$fh>;
$fh->close;
}
[download]

something goes wrong. The file is found (message "open filename" is printed, with filename being the correct name of the file), but then I get this error from the I0::File package:

Can't call method "open" on an undefined value

In other words, it's like there is no string assigned to the variable $file!

Comment on simple to describe I/O problem Select or Download Code

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Re: simple to describe I/O problem by Laurent_R (Canon) on Sep 01, 2014 at 20:38 UTC
I fail to see the usefulness of such a complicated construct: `use IO::File; # ... my $fh=IO::File->new; if ($fh->open($file,"<")) { # ...` [download] when the whole thing can be done in just one single line of code: `open my $fh, "<", $file or die "Can't open $file $!";` [download] To me, this is just looking like pointless over-engineering. Or perhaps OO-fashion victim. Or an application of the following principle: why should we make things simple when they can be made more complicated? Just the contrary of the Perl principles stated many times by Larry Wall and others: to make easy jobs easy.	[reply] [d/l] [select]
Re^2: simple to describe I/O problem by Anonymous Monk on Sep 01, 2014 at 20:54 UTC
I believe one of the advantages of using IO::Handle (from which IO::File inherits) is to have a little more control on a per-handle basis, such as being able to do `$io_handle->autoflush(1)`. Other than that I agree.	[reply] [d/l]
Re^3: simple to describe I/O problem by Laurent_R (Canon) on Sep 01, 2014 at 21:01 UTC
Agreed. I am not saying that that the IO::xxx hierarchy is useless, but just that, in the case in point, this seems to be overkill.	[reply]
Re: simple to describe I/O problem by Anonymous Monk on Sep 01, 2014 at 19:20 UTC
See the documentation of IO::File: you need to initialize your `$fh` like so: `my $fh=IO::File->new;` before you use it.	[reply] [d/l] [select]
Re: simple to describe I/O problem by Anonymous Monk on Sep 01, 2014 at 19:25 UTC
In addition to the above, your arguments to `open` are wrong, see IO::File. Try this instead: `... my $fh=IO::File->new; if ($fh->open("$file","<")) { ...` [download]	[reply] [d/l] [select]
Re^2: simple to describe I/O problem by AnomalousMonk (Archbishop) on Sep 01, 2014 at 19:46 UTC
`if ($fh->open("$file","<")) { ... }` Why does the string `$file` have to be interpolated into another string `"$file"` before being passed to the `open` method?	[reply] [d/l] [select]
Re^3: simple to describe I/O problem by Anonymous Monk on Sep 01, 2014 at 20:04 UTC
It doesn't, `"$file"` was just a remnant of (too) quickly editing the OP's code. (Unless maybe `$file` is an object with overloaded stringification; but then it'd probably be stringified inside `open`...)	[reply] [d/l] [select]
Re^2: simple to describe I/O problem by dottornomade (Initiate) on Sep 01, 2014 at 20:00 UTC
Thank you. My bad, it was a trivial mistake, it works now :)	[reply]