Hi bluhm, Thanks for your reply!
Honestly, I am still a little confused: > But before you plugged the fd leak, "nohup true 2>&-" would write to nohup.out. "nohup true 2>&-" means close stderr of nohup, right? > errno = 0; > if (isatty(STDOUT_FILENO) || errno == EBADF) Since we close stderr, why do we need additional check of stdout here? Thanks in advacne! On 9/9/2018 7:39 AM, Alexander Bluhm wrote: > On Sat, Sep 08, 2018 at 08:47:28PM +0800, Nan Xiao wrote: >> I don't think need "if (fd > STDERR_FILENO)" cause the fd is a new >> opened file descriptor. If its value is less or equal than >> `STDERR_FILENO', it means the stdin or stderr is already closed >> intentionally. So it should be OK close fd again. > > In general it is a bad idea to start programs without opened 0 1 2 > file descriptors. Then the next open will fill the gap and a > printf() or err() may write to random files. > > Some paranoid daemons like syslogd(8) dup2 /dev/null to them. And > there is this check: > if (nullfd > 2) > close(nullfd); > > If course nohup(1) is not that paranoid. And the isatty() checks > prevent that the stdio file decriptor gaps get filled. But before > you plugged the fd leak, "nohup true 2>&-" would write to nohup.out. > > Perhaps we could make nohup(1) a bit more sane by checks like this. > > errno = 0; > if (isatty(STDOUT_FILENO) || errno == EBADF) > > bluhm > -- Best Regards Nan Xiao
