FAQ 5.9 How can I make a filehandle local to a subroutine? How do I pass filehandles between subrou


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This is an excerpt from the latest version perlfaq5.pod, which
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5.9: How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles?

As of perl5.6, open() autovivifies file and directory handles as
references if you pass it an uninitialized scalar variable. You can then
pass these references just like any other scalar, and use them in the
place of named handles.

open my $fh, $file_name;

open local $fh, $file_name;

print $fh "Hello World!\n";

process_file( $fh );

If you like, you can store these filehandles in an array or a hash. If
you access them directly, they aren't simple scalars and you need to
give "print" a little help by placing the filehandle reference in
braces. Perl can only figure it out on its own when the filehandle
reference is a simple scalar.

my @fhs = ( $fh1, $fh2, $fh3 );

for( $i = 0; $i <= $#fhs; $i++ ) {
print {$fhs[$i]} "just another Perl answer, \n";

Before perl5.6, you had to deal with various typeglob idioms which you
may see in older code.

open FILE, "> $filename";
process_typeglob( *FILE );
process_reference( \*FILE );

sub process_typeglob { local *FH = shift; print FH "Typeglob!" }
sub process_reference { local $fh = shift; print $fh "Reference!" }

If you want to create many anonymous handles, you should check out the
Symbol or IO::Handle modules.


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