[Python-bugs-list] [ python-Bugs-514345 ] pty.fork problem

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Bugs item #514345, was opened at 2002-02-07 08:21
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=514345&group_id=5470

Category: Python Library
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: M.-A. Lemburg (lemburg)
>Assigned to: Fred L. Drake, Jr. (fdrake)
Summary: pty.fork problem

Initial Comment:
Subject: 
         Python bugreport, pty.fork problem
    Date: 
         Thu, 07 Feb 2002 07:30:08 -0800
   From: 
         Ronald Oussoren <oussoren@cistron.nl>
      To: 
         mal@lemburg.com


Sorry about the e-mail, but the bugtracker on SF doesn't 
accept my bugreport (I don't have a SF account).

The following script never returns:

----------------- start of script -------------
import pty
import os
import sys

def test():
        pid, fd = pty.fork()

        if pid == 0:
                print "1"
                print "2"
                print "3"
        else:
                fp = os.fdopen(fd, 'r')
                ln = fp.readline()
                while ln:
                        print '-->', ln
                        ln = fp.readline()
                print '-->', ln

test()
------------------ end of script -----------------
It prints '-->1' to '-->3' and then blocks. 

I've tested this with python 2.1 on Solaris 8. On Solaris 
pty.open seems to use 'openpty' instead of 'os.openpty'. A 
2-line change fixed the problem for me, but not for this 
demo-script: Close 'slave_fd' when pid != CHILD.




----------------------------------------------------------------------

>Comment By: Guido van Rossum (gvanrossum)
Date: 2002-02-08 13:58

Message:
Logged In: YES 
user_id=6380

Assigning to Fred, who appears to have hacked this module
before.

I cannot reproduce the problem, but I see a different
problem that may be hinting at the same issue:

Under Python 2.1 or before, on Red Hat Linux 7.2, the test
program for me prints this:

--> 1

--> 2

--> 3

--> 

and exits. But with Python 2.2, it prints:

--> 1

--> 2

--> 3

Traceback (most recent call last):
  File "/tmp/tpty.py", line 20, in ?
    test() 
  File "/tmp/tpty.py", line 17, in test
    ln = fp.readline() 
IOError: [Errno 5] Input/output error

How can the difference be explained? I like the pre-2.2
behavior better!

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