dup2

pub fn dup2(sync: *CancelRegion.Sync, old_fd: fd_t, new_fd: fd_t) DupError!void {
    while (true) {
        try sync.cancel_region.await(.nothing);
        switch (linux.errno(linux.dup2(old_fd, new_fd))) {
            .SUCCESS => return,
            .BUSY, .INTR => {},
            .INVAL => |err| return errnoBug(err), // invalid parameters
            .BADF => |err| return errnoBug(err), // use after free
            .MFILE => return error.ProcessFdQuotaExceeded,
            .NOMEM => return error.SystemResources,
            else => |err| return unexpectedErrno(err),
        }
    }
}