File handle as argument

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

Hi all
Can i send a file handle as a argument to a subroutine
eg:
Consider I have a file called /xxx/abc.txt
open(IN,'/xx/abc.txt');
can i have this file handle (anyway it is just like a array or scalar reference :) i think that filehandle is going to be a reference if wrong please correct me) passed as argument to a subroutine. If i can pass it as an argument please mention how to implement it. Please guide me if i am wrong and explain in what way a file handle is actually internally manipulated in Perl.
Thankyou

Comment on File handle as argument

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Re: File handle as argument
by bobf (Monsignor) on Jun 03, 2005 at 07:28 UTC

If you open a file using a filehandle, you can create a reference to it (by creating a reference to the typeglob) and then pass the reference to subs:

open( FH, '>', $filename ) or die $!;
my $ref2fh = \*FH;

foo( $ref2fh );
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My preferred method, though, is to open the file using a lexical variable (which eliminates the typeglob business):

open( my $fh, '>', $filename ) or die $!;

foo( $fh );
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See the section entitled "File and directory handles can be autovivified" in perldelta for perl 5.6 for more info on opening files using scalar variables (perl56delta on CPAN). This info is also in perlopentut under "Indirect Filehandles".

HTH

Update: added a link for perldelta

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Re: File handle as argument
by spurperl (Priest) on Jun 03, 2005 at 06:41 UTC

Without references: use globs like this - foo(*FH). Then in "foo" you just use my $fh = shift; And $fh can be plugged in like a file-handle, in "print", for example.

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Re: File handle as argument
by PodMaster (Abbot) on Jun 03, 2005 at 06:32 UTC

perldoc perlsub

foo(\*HANDLE);
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MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

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