stat or, more conveniently, the -w file test operator. Both work fine on open handles, though we're mostly used to feeding them file names.
Update: Oops, got the wrong end of the stick. Here's how to check the open flags to see if the handle is currently writable:
use Fcntl;
sub writable {
my $fh = shift;
(O_WRONLY | O_RDWR) & fcntl( $fh, F_GETFL, my $slush);
}
for (qw/ > < >> +< +> /) {
open my $fh, $_, 'foo' or warn $! and next;
print
"$_\t",
writable($fh)? 'writable.': 'not writable.',
$/;
}
__END__
> writable.
< not writable.
>> writable.
+< writable.
+> writable.
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