🚀 go-pugleaf

In article <9211051448.AA24758.SM@odin.INS.CWRU.Edu>, chet@odin.ins.cwru.edu (Chet Ramey) writes:
> This is a bug alright, but it's a bug with rshd that's not fixed until
> 4.3-reno.
> 
> rshd sets up a pipe (int pv[2]; if you have the source to the tahoe rshd)
> to the process it executes and uses it to manage error and control output
> from over the net.  In the child process, it does a dup2(pv[1], 2), but
> never calls close(pv[1]).  Adding that code to the 4.3-tahoe rshd makes it
> (and the Xemacs script) work right.
> 
> I don't know how to solve this cleanly in bash.  Doing a blanket close of
> all open file descriptors > 2, < 20 is a no-no, especially when we're not
> interactive.  csh `works' because it does the blanket close on startup, but
> csh can get away with doing that because it doesn't let you manipulate
> arbitrary file descriptors.

At least on this machine the problem appears to be more that just one
with rsh. For years I have been using the exec n>&- trick to fix the
rsh problem. (Where n is the problem file desciptor). With the
current version of bash, that doesn't seem to work.

I have a program called "nfiledes" which figures out what file desciptors
are open:

    cronus:-dall $ bash
    cronus:-dall $ exec nfiledes
    File descriptor 5 open.
    File descriptor 2 open.
    File descriptor 1 open.
    File descriptor 0 open.
    4 file descriptors open across execs.
    cronus:-dall $ bash
    cronus:-dall $ exec nfiledes 5>&-
    File descriptor 10 open.
    File descriptor 2 open.
    File descriptor 1 open.
    File descriptor 0 open.
    4 file descriptors open across execs.


Note that as soon as I try and close file desciptor 5, something (and
I can't think how it could be anything except bash) opens a new file
descriptor (10). (And if I close 10 it opens 11).


This is
    BASH_VERSION=1.12.1

on a DECstation 5000 (mips R3000) running Ultrix 4.2.

Here is the source for nfiledes.c

/* Count the number of file descriptors currently open */
#include <stdio.h>
#include <fcntl.h>
main ()
{
  int ret, i, n = 0;
  for ( i = _NFILE; i--;)
    if ( (ret = fcntl(i, F_GETFD, 0)) != -1)
      {
	printf("File descriptor %d open.\n", i);
	n += (!ret) & 1;
      }
  printf("%d file descriptors open across execs.\n", n);
}


Ian
-- 
Ian Dall          I'm not into isms, but hedonism is the most
                  harmless I can think of. -- Phillip Adams

internet: dall@hfrd.dsto.gov.au