fileno
fileno filehandle
Returns the file descriptor for a filehandle. (A
file descriptor is a small integer, unlike the filehandle, which
is a symbol.) It returns undef
if the handle is not open. It’s useful for constructing bitmaps
for select
and for passing to
certain obscure system calls if syscall
is implemented. It’s also useful
for double-checking that the open
function gave you the file
descriptor you wanted.
3.145.12.3