From: PerlFAQ Server on
This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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5.13: How can I open a filehandle to a string?

(contributed by Peter J. Holzer, hjp-usenet2(a)hjp.at)

Since Perl 5.8.0 a file handle referring to a string can be created by
calling open with a reference to that string instead of the filename.
This file handle can then be used to read from or write to the string:

open(my $fh, '>', \$string) or die "Could not open string for writing";
print $fh "foo\n";
print $fh "bar\n"; # $string now contains "foo\nbar\n"

open(my $fh, '<', \$string) or die "Could not open string for reading";
my $x = <$fh>; # $x now contains "foo\n"

With older versions of Perl, the "IO::String" module provides similar
functionality.



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From: Justin C on
On 2010-07-27, PerlFAQ Server <brian(a)theperlreview.com> wrote:
> 5.13: How can I open a filehandle to a string?
>
> (contributed by Peter J. Holzer, hjp-usenet2(a)hjp.at)
>
> Since Perl 5.8.0 a file handle referring to a string can be created by
> calling open with a reference to that string instead of the filename.
> This file handle can then be used to read from or write to the string:
>
> open(my $fh, '>', \$string) or die "Could not open string for writing";
> print $fh "foo\n";
> print $fh "bar\n"; # $string now contains "foo\nbar\n"
>
> open(my $fh, '<', \$string) or die "Could not open string for reading";
> my $x = <$fh>; # $x now contains "foo\n"

I can see how it works, but I wonder in what circumstances one might
want to do this?

Justin.

--
Justin C, by the sea.
From: Peter J. Holzer on
On 2010-07-28 10:04, Justin C <justin.1007(a)purestblue.com> wrote:
> On 2010-07-27, PerlFAQ Server <brian(a)theperlreview.com> wrote:
>> 5.13: How can I open a filehandle to a string?
>>
>> (contributed by Peter J. Holzer, hjp-usenet2(a)hjp.at)
>>
>> Since Perl 5.8.0 a file handle referring to a string can be created by
>> calling open with a reference to that string instead of the filename.
>> This file handle can then be used to read from or write to the string:
>>
>> open(my $fh, '>', \$string) or die "Could not open string for writing";
>> print $fh "foo\n";
>> print $fh "bar\n"; # $string now contains "foo\nbar\n"
>>
>> open(my $fh, '<', \$string) or die "Could not open string for reading";
>> my $x = <$fh>; # $x now contains "foo\n"
>
> I can see how it works, but I wonder in what circumstances one might
> want to do this?

Sometimes you have a module which is intended to read from a file. But
you have the data already in memory. Of course you could write it to a
temporary file and then invoke the module to read it back. But that's
not very elegant - much better if you can tell it to read from a scalar.
Same thing the other way: You have a module which can only write to a
file but you need the output in a variable.

I regularly use this in test scripts.

hp
From: Justin C on
On 2010-07-28, Peter J. Holzer <hjp-usenet2(a)hjp.at> wrote:
> On 2010-07-28 10:04, Justin C <justin.1007(a)purestblue.com> wrote:
>> On 2010-07-27, PerlFAQ Server <brian(a)theperlreview.com> wrote:
>>> 5.13: How can I open a filehandle to a string?
>>>
>>> (contributed by Peter J. Holzer, hjp-usenet2(a)hjp.at)
>>>
>>> Since Perl 5.8.0 a file handle referring to a string can be created by
>>> calling open with a reference to that string instead of the filename.
>>> This file handle can then be used to read from or write to the string:
>>>
>>> open(my $fh, '>', \$string) or die "Could not open string for writing";
>>> print $fh "foo\n";
>>> print $fh "bar\n"; # $string now contains "foo\nbar\n"
>>>
>>> open(my $fh, '<', \$string) or die "Could not open string for reading";
>>> my $x = <$fh>; # $x now contains "foo\n"
>>
>> I can see how it works, but I wonder in what circumstances one might
>> want to do this?
>
> Sometimes you have a module which is intended to read from a file. But
> you have the data already in memory. Of course you could write it to a
> temporary file and then invoke the module to read it back. But that's
> not very elegant - much better if you can tell it to read from a scalar.
> Same thing the other way: You have a module which can only write to a
> file but you need the output in a variable.
>
> I regularly use this in test scripts.

Thank you for the explanation. I suppose I've either never used a module
like that or I've always gone the long way round. I will try to keep
this in mind should I encounter such a problem.

Justin.

--
Justin C, by the sea.