in reply to Write to and read from scalar

use strict;
use warnings;

my $str;

open my $fOut, '>', \$str;
print $fOut "Hello World\n";
close $fOut;

open my $fIn, '<', \$str;
my $inStr = <$fIn>;
close $fIn;

print $inStr;

[download]

Prints:

Hello World

[download]
True laziness is hard work

Replies are listed 'Best First'.
Re^2: Write to and read from scalar
by wwe (Friar) on Mar 23, 2012 at 08:49 UTC
    Hi, I'm not really sure I get the point. This can be done with a simple assignment $variable = 'xyz'. Then you just print this varible with print $variable. If this is not wat you are looking for please try to describe the problem other way.
[reply]
[d/l]
[select]

      The point is that certain functions expect to be passed filehandles for various purposes.

      Sometimes the data you want to pass to these functions is actually held in a variable. The naive way of coping with that is to write out your data to a temporary file, open the file and pass the filehandle to the function. Often a better solution though is to construct a filehandle which points straight to the scalar variable, and not to a real file on disk.

      Grandfather provides one technique, supported by Perl 5.8+. If (for some perverse reason) you want to support earlier releases of Perl, then IO::String also provides a solution using tied filehandles.

      perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
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Re^2: Write to and read from scalar
by flexvault (Monsignor) on Mar 23, 2012 at 13:02 UTC

    GrandFather,

    I did it this way from your example. I would not have known how to do this, but the disk file is basically a representation of the scalar. 

    my $str = "Hello World\n";

open my $fIn, '<', \$str;
my $inStr = <$fIn>;
close $fIn;

print $inStr;

    [download]

    Is there a reason to use file I/O to the scalar?

    Thank you

    "Well done is better than well said." - Benjamin Franklin

[reply]
[d/l]

      For one use reread the OP's node. I frequently use the technique when answering SoPW's where an input file is required. I could write a temporary file then use that, but that adds clutter to the sample.

      In real applications I've used the technique to cache parts of a file that I need to access frequently and to provide a file handle for modules that require them when I really want to pass in a string.

      True laziness is hard work
[reply]

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