Return file descriptor from filehandle

Daftar Isi

• fileno FILEHANDLE

  Returns the file descriptor for a filehandle, or undefined if thefilehandle is not open. If there is no real file descriptor at the OSlevel, as can happen with filehandles connected to memory objects viaopen with a reference for the third argument, -1 is returned.

  This is mainly useful for constructingbitmaps for select and low-level POSIX tty-handling operations.If FILEHANDLE is an expression, the value is taken as an indirectfilehandle, generally its name.

  You can use this to find out whether two handles refer to thesame underlying descriptor:

   if (fileno(THIS) == fileno(THAT)) {
   
   print "THIS and THAT are dups\n";
   
   }