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M-x shell not working


From: Sunil Yeddu
Subject: M-x shell not working
Date: Mon, 17 Oct 2005 23:34:45 -0700

Hi all,
      We have recently migrated to emacs 21.4 from emacs 20.7 in our environment. In emacs-21.4, I get this error when I do M-x shell.
Warning: no access to tty (Bad file descriptor).
Thus no job control in this shell.
stty: standard input: Invalid argument
exit

Process shell finished

    
We use clearcase for source control and this is happening inside a clearcase view. Outside a view,  there is no problem. We had no problem at all in emacs-20.7,  even inside a clearcase view. In emacs-21.4, it is working some times but most of the times it is not. Looks like pty is not being allocated.
    I did some debugging and found the following information. In emacs-21.4, in the rare case when M-x shell works,  tty allocated is like '/view/dev/ttyp7' . '/view'  is due to clearcase, may be some virtual path. The actual path starts from '/dev/...' ie. Removing '/view' would give the path of the tty in our system. In emacs-20.7, the tty allocated is like '/view/43'. It is always of the form '/view/' followed by a number. This indicates that the tty allocation system is changed in emacs-21.4. In emacs-20.7, looks like it is doing some virtual allocation as it is just a number. But in emacs-21.4, it is allocating from /dev. We have sufficient number of ttys too.
% ls /dev/tty* | wc -l
    905
   Emacs is not able to pick up a free one? Also I noticed that, in emacs-21.4, when M-x shell works, it works for some time before it stops working and goes back to its usual state. During this time, it is able to allocate ptys in serial order without any problem, when we invoke shell from different emacs sessions. I suspect that when it is able to capture some tty in a specific range, it is able to obtain the remaining without any problem. I ruled out the possibility that ttys are really exhausted because, while I could open shell from emacs-21.4, other users could'nt do it on the same machine during the same time.
   OS is linux. I have verified that process-connection-type is set to t. So this is not the same problem as Mac users have reported. Also, I started emacs with -q option. So there is nothing in my .emacs file which could have caused this problem.
  I hope this infomation which I collected from my debugging would be of help. I could not proceed further. Can someone help?

Sunil


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