Re: About-me-password backend

["Johannes H. Jensen" <joh deworks net>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Great, thanks for the tip!

Best regards,

Johannes H. Jensen
deworks


On 11. apr. 2006, at 14:36:08, Gustavo J. A. M. Carneiro wrote:

>   Note that glib already has g_child_watch_add, which is a lot simpler
> and safer to use than signal().  In the callback you can see what  
> status
> the child returned and if it received a signal instead.
>
>   Regards.
>
> On Ter, 2006-04-11 at 09:42 +0100, Darren Kenny wrote:
> > Hi Johannes,
> >
> > The most correct way to handle the status of a child process is to  
> > catch
> > the unix signal 18 - SIGCHLD - this should be fired by the OS  
> > (assuming
> > unix based) should the fork/execed process exit.
> >
> > So you need to set up a signal handler for SIGCHLD, before you  
> > enter the
> > processing loop, and have this signal handler store the pid of the
> > passwd process so that later you can check if this is the one that  
> > exited.
> >
> > Meanwhile, a loop with a  read on an file descriptor (e.g. waiting  
> > for
> > the "Password: " string from passwd) will be interrupted due to the
> > SIGCHLD and return -1, and errno will be set to EINTR - if you  
> > check for
> > these conditions and then call the child_exited call then you should
> > know if passwd exited.
> >
> > For example:
> >
> >     signal( SIGCHLD, reapChildProcess );
> >     while ( ! done ) {
> >         if (read(...) < 0 ) {
> >             if ( errno == EINTR && child_exitied( passwd_pid) ==  
> > TRUE ) {
> >                 done = TRUE; /* or whatever you want to do to exit  
> > gracefully */
> >                 continue; /* or break if you want to force exit of  
> > the loop */
> >             }
> >         }
> >         /* normal processing */
> >     }
> >
> >
> > (BTW, I'm assuming you don't have multiple processes forked, if  
> > you do
> > you probably need to store the last N processed exited for check  
> > to work).
> >
> > There should be loads of examples of this type of thing on the net...
> >
> > Darren.
> >
> > Johannes H. Jensen wrote:
> > > Dear almighty GNOME hackers, I'm in need of some pointers!
> > >
> > > I'm currently hacking on the about-me password dialog (see #321567),
> > > which is spawning /usr/bin/passwd to authenticate and change the
> > > password. In the new dialog, I'm dividing the process in two, so  
> > > that
> > > the user has to authenticate with his current password first (which
> > > spawns passwd to verify). If passwd doesn't complain and prompts for
> > > the new password, he can enter his new password, retype it and hit
> > > "Change password". When he hits the button, some time has elapsed
> > > since he first authenticated (and thus passwd was spawned).
> > >
> > > Now my question is, what happens if passwd suddenly dies during that
> > > time period? Is it likely it will? If so, what's the best way to
> > > periodically(?) ensure that the process is running? Check every n
> > > seconds with waitpid() in the main loop? As far as I can see,  
> > > this is
> > > how it's done in the current version - wait_child() is called  
> > > every 4
> > > seconds to check what the backend is doing...
> > >
> > > Any pointers greatly appreciated :)
> > >
> > > Btw, a more detailed mockup of the program/process flow can be found
> > > at http://joh.deworks.net/password-dialog/GnomeAboutMePassword.html
> > >
> > > Best regards,
> > >
> > > Johannes H. Jensen
> > > deworks
> > >
> > >
> > > _______________________________________________
> > > desktop-devel-list mailing list
> > > desktop-devel-list gnome org
> > > http://mail.gnome.org/mailman/listinfo/desktop-devel-list
> > _______________________________________________
> > desktop-devel-list mailing list
> > desktop-devel-list gnome org
> > http://mail.gnome.org/mailman/listinfo/desktop-devel-list
> --
> Gustavo J. A. M. Carneiro
> <gjc inescporto pt> <gustavo users sourceforge net>
> The universe is always one step beyond logic.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (Darwin)

iD8DBQFEPsmx3qI8abXZ8HcRAjOpAJ94nz64cd38SZnpewzyV/LXRpTsJQCeO8P2
xwZ72lJhJrVopgvo3hNpfv0=
=atbc
-----END PGP SIGNATURE-----