Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl-Sensitive Sunglasses

How to dup $FOO to STDIN

by belg4mit (Prior)
on Nov 15, 2001 at 11:14 UTC ( #125521=perlquestion: print w/replies, xml ) Need Help??

belg4mit has asked for the wisdom of the Perl Monks concerning the following question:

I have a scalar filehandle and I want to dup it to STDIN. Globbing just gets me a scalar $STDIN equivalent to $FOO. The open dup syntax open(STDIN, ">&$FOO") doesn't work either; me thinks for obvious reasons the waka is in the wrong direction but flipping it doesn't help.

Replies are listed 'Best First'.
Re: How to dup $FOO to STDIN
by jeroenes (Priest) on Nov 15, 2001 at 12:25 UTC
    Hmmm. It took some time to figure out what you really wanted, until I figured to check 'info dup'. And there it was: You want to simply duplicate the filehandle. You can go several ways here. But first:

    You should not use caps for variable names, only for fileglobs. All caps names may cause conflicts with later versions of perl. Moreover, it is confusing, and maybe causing you to do the wrong thing.


    1. Use a GLOB, and glob it to STDIN like:
      open FOO, "<filename" or die ...; *STDIN = *FOO;
      Not really neat, even confusing maybe, but should work.
    2. The open dup as described in perldoc perlopentut
      my $fileno = fileno( $foo ); open STDIN, ">&$fileno" or die "Could not open $fileno: $!";
    3. Just check 'perldoc perlipc' and IPC::Open2 for good measure.


    "We are not alone"(FZ)

      #1 doesn't meet the criterion of duping a scalar filehandle (which I need because this is hapenning in parallel forks).

      #2 Works!

      #3 I had looked at perlipc but found nothing for dupping STDIN or scalar filehandles.


      PS> "shouldn't not use caps" so I should then? ;-) Yeah wog has gotten on me about that too. I've cut back, but am still using for "globals" or effectively just scalar filehandles, so they lok like regular filehandles.

      -- perl -p -e "s/(?:\w);(<A HREF="/">st< +/A>)/'\$1/mg"
        Already figured you wanted to do something with childs or the like, that's why I added the ipc stuff. It actually describes named pipes, and the use of open for ipc.

        On the caps: :-) && You shouldn't. Fileglobs are in caps because they are really special. Filehandles are less magical.

Log In?

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: perlquestion [id://125521]
Approved by root
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others exploiting the Monastery: (2)
As of 2022-05-17 20:16 GMT
Find Nodes?
    Voting Booth?
    Do you prefer to work remotely?

    Results (68 votes). Check out past polls.