Question

I am trying to determine if a given scalar holds a filehandle. It could have been passed to me from a bareword filehandle (i.e. \*FH), a lexical filehandle, an IO::Handle, an IO::File, etc. So far, the only thing that seems to be consistent amongst the various flavors is that they all have a reftype of "GLOB".

Answer 1

Use the openhandle function from Scalar::Util:

openhandle FH

Returns FH if FH may be used as a
filehandle and is open, or FH is a
tied handle. Otherwise undef is
returned.

  $fh = openhandle(*STDIN);           # \*STDIN
  $fh = openhandle(\*STDIN);          # \*STDIN
  $fh = openhandle(*NOTOPEN);         # undef
  $fh = openhandle("scalar");         # undef

The current implementation is similar to Greg Bacon’s answer, but it has some additional tests.