* Wesley J. Landaker ([EMAIL PROTECTED]) wrote: > I'm not the maintainer, but use netcat a lot. Here are some comments:
Hi Wesley, Thanks for the reply. > On Saturday 14 May 2005 10:55, Dr. David Alan Gilbert wrote: > > I'm trying to shovel a large amount of data (800GB) between two > > machines, so have a pair of tar's running over netcat as follows: > > > > on the source: > > > > tar -clf- . | nc destination 6666 > > First of all, did only one, or both of these commands actually result in a > message from your shell telling you it was waiting for stdin? It really > makes a difference: > > If this one was looking for input, it would have had to have been tar, not > netcat, as netcat's stdin is tied to tar's stdout, so it couldn't have > blocked the shell; only tar could have. Did this one say that the program > was waiting for input, or was it just the other one below? It was only the nc -l on the destination machine that was waiting for input. > > on the destination: > > > > nc -l -p 6666 | tar -xpf - > > > > I had these running in a background'ed nohup and after a while the > > copying stopped and bash told me that the backgrounded destination > > package had stopped waiting for input; sure enough I 'fg'd > > it and hit return a few times and it carried on its way. > > I'm not sure why netcat would be blocking on input here (it only does > non-blocking reads in it's main I/O function (readwrite), but if this > happened to you on this command line, that is where the bug mostly like > lives. =) Indeed - I also strace'd it at one point when it hung and saw it waiting on a read of fd 0 which was still the terminal I'd run it from. > There is an easy workaround for either case (bug or not), though: when you > run that command, you're leaving netcat's stdio hooked to your terminal. > I'd suggest tying it's stdin off to /dev/null, with something like: Indeed - (or perhaps from a 'yes' if it really wants the carriage return.) - but it was already 50GB in and I'd hoped it wouldn't happen again. Dave -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux on Alpha,68K| Happy \ \ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex / \ _________________________|_____ http://www.treblig.org |_______/ -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
