How can I check if a filehandle is open in Perl? [duplicate]

Answer 1

The Scalar::Util module provides the openhandle() function for this. Unlike fileno(), it handles perl filehandles which aren't associated with OS filehandles. Unlike tell(), it doesn't produce warnings when used on an unopened filehandle From the module's documentation:

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