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I was poking around in Perl 5.8.0's core module library, and turned up a new form of open that I hadn't heard about. It happens in lib/5.8.0/{arch}/PerlIO/scalar.pm

Something I've occasionally wanted to do is to attach a file handle to a string as an accessor. That has been possible with earlier perl using IO::Scalar or IO::Stringy, but not all filehandle semantics and conventions were honored. I found that that is native in 5.8.0 with PerlIO, and that the syntax is as simple as could be imagined: open FILEHANDLE, MODE, SCALARREF.

That's it - give open a reference to the string in the file name slot, and it works. The handle may be read, written, or appended. Globals like $/ work as expected.

Here's a sledgehammer-on-peanut example which prints a string in cable-ese (upper case, suppressed spaces, five letter groups):

my $foo= 'Now is the time for all good men to come to the aid of their + country'; { local $\ = " "; local $/ = \5; $foo =~ tr/ //d; open my $fh, '<', \$foo; print uc while <$fh>; }

As an output file:

my $foo; $_ = "She sells sea shells by the sea shore"; { local $\ = $/; open my $fh, '>', \$foo; print $fh $_ for split; } print $foo;

Append, capturing STDERR:

my $oops; open STDERR, '>>', \$oops;

I've only started to explore this trick. I haven't tried flock or seek/tell or $.. I haven't tinkered with truncate or exotic modes.

Here's a challenge. Can you find any limits to file-like behavior? What cool uses can you think of for this?

After Compline,
Zaxo


In reply to Open Has a New Trick by Zaxo

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