How do I redirect STDOUT to a string?

pm5 has asked for the wisdom of the Perl Monks concerning the following question:

Since this works:

use IO::Handle;
use IO::File;

my $out = IO::File->new('output.txt', 'w') or die $!;
STDOUT->fdopen($out, 'w')
    or die $!;
print "hello, world!";
[download]

I thought this should work:

use IO::Handle;
use IO::Scalar;

my $data = '';
my $out = IO::Scalar->new(\$data) or die $!;

STDOUT->fdopen($out, 'w')
    or die $!;
print "hello, world!";
[download]

Alas it does not. I'm trying to save the printed output of 3rd party code in a string for further use. How do I do this?

Comment on How do I redirect STDOUT to a string? Select or Download Code

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Re: How do I redirect STDOUT to a string? by jZed (Prior) on Jun 23, 2004 at 05:02 UTC
`use IO::Scalar; $std_out = tie *STDOUT, 'IO::Scalar'; print "hello world"; # goes into $std_out scalar;` [download]	[reply] [d/l]
Re: How do I redirect STDOUT to a string? by BrowserUk (Patriarch) on Jun 23, 2004 at 06:35 UTC
If your using 5.8.x, then you can use the "in-memory file" form of open. #! perl -slw use strict; sub IO2Mem{ my( $memRef, $mode, $io ) = @_; die 'Usage: IO2Mem( scalarRef [, mode] )' unless ref $memRef eq 'SCALAR'; open $io, $mode \|\| '>', $memRef or die $!; return select $io; } my $memory; my $saved = IO2Mem( \$memory ); print 'Hello world!' for 1 .. 10; $memory =~ s[o w][o, W]g; select $saved; print $memory; __END__ P:\test>test2 Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! Hello, World! [download] Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail "Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon	[reply] [d/l]
Re: How do I redirect STDOUT to a string? by leriksen (Curate) on Jun 23, 2004 at 05:00 UTC
You could try Filter::Handle - thats what I do. Be careful though - it was broken in one part by a change in the underlying Perl IO in 5.8+, so some of the test cases for its 'make test' fail. But if you dont need those bits, its great. +++++++++++++++++ #!/usr/bin/perl use warnings;use strict;use brain;	[reply]
Re: How do I redirect STDOUT to a string? by slife (Scribe) on Jun 23, 2004 at 07:45 UTC
The "old school" way of doing this was by juggling the current default filehandle with select(), e.g.: `my $oldfh = select STDOUT; my $out = IO::File->new('output.txt', 'w',) or die $!; select $out; # Do something involving print(). It will go to output.txt. # Be nice and give back STDOUT select $oldfh;` [download] This functionality is nicely wrapped in the oft-forgotten SelectSaver module (part of the Perl core distribution). NB - don't confuse this version of select() with the four-argument version, which reports whether a file descriptor is ready for read/write.	[reply] [d/l]
Re: How do I redirect STDOUT to a string? by DrHyde (Prior) on Jun 23, 2004 at 08:47 UTC
IO::Capture::Stdout	[reply]
Re: How do I redirect STDOUT to a string? by Anonymous Monk on Jun 23, 2004 at 22:42 UTC
You could use backticks, too. my $stdout=`ls`; [download] or, perl will fill an array of stdou't lines: my @stdout=`ls -al`; [download] -vlad	[reply] [d/l] [select]