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Re: Help on /dev/tty and su -c



On Thu, 15 Mar 2012 11:40:49 -0600 Bob Proulx wrote:

> Francesco Poli wrote:
[...]
> > The most general issue is that apt-listbugs needs to perform the
> > following steps (when run in "apt" mode):
> > 
> >   * first it reads some input through its STDIN, through a pipe
> > 
> >   * when this input ends (EOF), apt-listbugs needs to be able to become
> > interactive and ask questions to the user, and get answers from STDIN,
> > and possibly also run a web browser (that could be a textual browser,
> > depending on the user preferences) and let the user interact with the
> > browser
> 
> Being a long time Unix programmer the above two contraints appear to
> me to be opposing contraints that are not possible to accomplish in a
> portable way.

You're probably right, Bob.

> Sure you can hack around them in some hackish way.  But
> I do not think it is a good idea to do so since the hack will almost
> certainly come back to haunt you at some time in the future.
> Therefore I suggest addressing the issue at the source of the problem
> by restructuring it such that this problem is entirely avoided.
> 
> Is there no way to read the data piped data by some method other than
> standard input?  By using a named pipe or temporary file?  Then stdin
> will always be available for interactive use.

This would be a radical solution.
We are already trying to see whether this is possible: see
http://bugs.debian.org/662983#45

> 
> I am sorry but not being familiar with the structure requires me to
> ask some questions by which I hope the answers would lead someone to a
> better solution.  What is the root underlying reason for reading stdin
> for the data?  What is the framework which lead to that data flow
> design?

The constraints come from the apt Pre-Install-Pkgs hook info
protocol version 2, which is used by Apt (and compatible package
managers) to provide information (about packages being
installed/upgraded/downgraded/removed) to commands executed through the
Pre-Install-Pkgs hook mechanism.

Please see:
http://bugs.debian.org/662983#40
apt.conf(5) man page
http://bugs.debian.org/627188#68


Anyway, thanks a lot for your kind reply!

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