fileIsTty

fn fileIsTty(userdata: ?*anyopaque, file: File) Io.Cancelable!bool {
    const ev: *Evented = @ptrCast(@alignCast(userdata));
    var sync: CancelRegion.Sync = try .init(ev);
    defer sync.deinit(ev);
    while (true) {
        try sync.cancel_region.await(.nothing);
        var wsz: winsize = undefined;
        const rc = linux.ioctl(file.handle, linux.T.IOCGWINSZ, @intFromPtr(&wsz));
        switch (linux.errno(rc)) {
            .SUCCESS => return true,
            .INTR => {},
            else => return false,
        }
    }
}