[Patches] [ python-Patches-783050 ] pty.fork() compatibility code wrong?

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Fri Dec 22 19:42:44 CET 2006

Patches item #783050, was opened at 2003-08-04 16:02
Message generated for change (Comment added) made by akuchling
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>Category: Library (Lib)
Group: None
>Status: Closed
>Resolution: Accepted
Priority: 5
Private: No
Submitted By: Patrick Lynch (rvdp)
>Assigned to: A.M. Kuchling (akuchling)
Summary: pty.fork() compatibility code wrong?

Initial Comment:
pty.fork() provides compatibility code for environments 
lacking os.forkpty() 
This code is incorrect compared to the forkpty code in glibc, 
and will cause reading of the returned master_fd to hang 
indefinetly when the child process is finished. 
I am running on linux, Python 2.2. I am using the 
compatibility code where I need more control ( grabing 
stdout seperate to stderr, which is on the pty). 
To have it read like forkpty in glibc: 
    master_fd, slave_fd = openpty() 
    pid = os.fork() 
    if pid == CHILD: 
        # Establish a new session. 
        # Slave becomes stdin/stdout/stderr of child. 
        os.dup2(slave_fd, STDIN_FILENO) 
        os.dup2(slave_fd, STDOUT_FILENO) 
        os.dup2(slave_fd, STDERR_FILENO) 
        if (slave_fd > STDERR_FILENO): 
            os.close (slave_fd) 
        os.close( slave_fd) 
    # Parent and child process. 
    return pid, master_fd 
Reading the master_fd when the child is finished will now 
raise an IO error, same as the native forkpty(). 
I guess the story may be different on non linux boxen 


>Comment By: A.M. Kuchling (akuchling)
Date: 2006-12-22 13:42

Logged In: YES 
Originator: NO

Applied to the trunk in rev. 53146.  Thanks for pointing out this bug!


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