Re: Recovering msgs from system() or fork() with Gtk+

[Erik Mouw <J A K Mouw ITS TUDelft NL>]

On Sun, Apr 22, 2001 at 02:13:18PM +0000, Patrice St-Gelais wrote:
> I want to be able to start any command / application that could be given
> by the user from a gtk+ application:
>
> (1)    The task must be independant from parent gtk+ app, so that the
> user can continue the use the parent;

Sounds like fork() and exec().

> (2)    I want to recover the error message, when the user gives a not
> executable string, so that I can display it in a Gtk window.

man waitpid, or see the example in question 5.3 of the GTK+ FAQ.

> Suppose the application is a simple text editor.  Something could be
> done this way:
>
> system("gedit mytext &");
>
> Suppose now that the user makes a typo and gives "gedti".  Because
> "system" launches a shell, the execution is successful (given the shell
> is working).  It seems there is no way to recover the result of the
> command inside the shell.  The only way for the user to know there was a
> problem is to start the parent from an X console, where the child
> displays its error message.

You can always redirect stdout and stderr. For an example, download the
DOSemu code from www.dosemu.org, and have a look at the function
run_unix_command() in src/base/misc/dos2linux.c.

> I tried to use fork() followed by execlp()/execvp() in the child
> process.  Fork() works when the child process exits with  _exit()
> instead of exit().  Unfortunately, it doesn't work when I put a Gtk call
> in the child process for displaying the error message.  The message
> window displays, but hangs.  I've seen a message in this mailing list
> saying it is not supposed to work.  I don't know the details.

See question 5.3 in the GTK+ FAQ.


Erik
[leaving userland again to hack arm-linux kernels]

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Department
of Electrical Engineering, Faculty of Information Technology and Systems,
Delft University of Technology, PO BOX 5031,  2600 GA Delft, The Netherlands
Phone: +31-15-2783635  Fax: +31-15-2781843  Email: J A K Mouw its tudelft nl
WWW: http://www-ict.its.tudelft.nl/~erik/