- fileno FILEHANDLE
-
Returns the file descriptor for a filehandle, or undefined if the filehandle is not
open. This is mainly useful for constructing bitmaps for select and low-level
POSIX tty-handling operations. If FILEHANDLE is an expression, the value is taken as an
indirect filehandle, generally its name.
You can use this to find out whether two handles refer to the same underlying
descriptor:
if (fileno(THIS) == fileno(THAT)) {
print "THIS and THAT are dups\n";
}
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(Filehandles connected to memory objects via new features of open may
return undefined even though they are open.)
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