linux-kernel - Re: popen2 popen call

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Message-Id: <082720091839.15057.4A96D2D10002C02000003AD122230647029B0A02D2080C0A9B079D0A030EBF9F030E059B070A08@att.net>
Date:	Thu, 27 Aug 2009 18:39:13 +0000
From:	heitkamp@...ritech.net
To:	Andreas Schwab <schwab@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: popen2 popen call

-------------- Original message from Andreas Schwab <schwab@...hat.com>: -------------- 

> "F. Heitkamp" writes: 
> 
> > When the popen call is made in sshd/session.c I get a error from 
> > strerror of "Function not Implemented". 
> 
> Which function exactly returns this error? 

In the openssh source distribution there is a file, session.c that uses popen, with the
ultimate purpose of fixing the .Xauthority file for X11 forwarding.  It uses popen to set the DISPLAY, MIT-MAGIC-COOKIE etc. via the shell I think, executing xauth.  In session.c popen is used three times under different conditions.  I put strerror calls where the popen call returns a NULL pointer to try to find out why the popen call fails.  I could post the section of code if you want to see.  I am not a professional programmer.

The gist of it is:

fp = popen( cmdstr, "w" );
if ( !fp )
  /* call strerror, errno */
> 
> There is no such thing as a popen2 syscall. 

OK.  I read in one of the messages, that glibc, passes the popen call to a ABI in the kernel. I have not looked at the code in glibc yet.

Fred

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