Re: What is the minimum number of lines to update a gui window without user clicking a button

["L. D. James" <ljames apollo3 com>]

On 08/10/2013 07:09 PM, Chris Vine wrote:
> This appears to be just a batch job calling popen() which brings up a 
> ppp connection. There is no program loop anywhere and the while loop 
> for fgets() in runit() will block until EOF is reached, which equates 
> to the call to pppd ending and the process in which it is running 
> closing its stdout. Presumably you run this as a cron job, or 
> something like that? Or, since you say, "while it's running and 
> checking the connection it outputs either starts '*' or dots '.' at 10 
> second interval while it checks some of the file and connection 
> status", possibly you have excised the loop logic, which is the 
> interesting part for present purposes. (As it happens, it will not 
> compile because the prototype for runit() is not in namespace scope, 
> but that is no doubt just a matter of transcription.) To call up an 
> executable (in this case pppd) in this kind of usage using glib you 
> would normally use Glib::spawn_async_with_pipes() and connect to the 
> standard_output and standard_error file descriptors with 
> Glib::signal_io().connect(). The problem you have got here though is 
> that you call setuid(0) on a binary which presumably has its suid bit 
> set in order to launch pppd. You should definitely not do that 
> directly with a GTK+ program. You would need to have a small wrapper 
> with suid set which calls up pppd, which is launched by your GTK+ 
> program using Glib::spawn_async_with_pipes(). (Yuck.) As it happens, 
> if you want a short cut for a batch job like this which provides a 
> GTK+ user interface, I would consider a shell script and zenity, which 
> is what zenity was intended for. A google search will tell you more. 
> However you would still need to circumvent your setuid problem. Chris 

Hi, Chris.  I stripped down a 500 line C++ program and included some 
system calls to give you and example of my many C++ programs.  Many C++ 
programs use calls to the system shell.  I can tell that happening with 
a number of driver installations.

This application would not work as a bash script.  I mentioned to you 
that you can not set the suid bit on a bash script.

I'm familiar with cron jobs, and have no problems with cronjobs.  In 
fact some of my applications are run by cron.

The particular VPN connection application is run currently added to the 
Ubuntu dash and shows a black screen for the status when it's run.

By the way, there are gui applications for batch files, perl files and 
just about any other programming concept.

I appreciate your interest and your questions and suggestions.  I 
understand that I don't have to use or learn gtkmm.  But I hope you 
don't mind my interest in the facility.

Some of my applications do not use any system calls.  Some of them use 
some system calls.  But I would like for most of them to output to a gui 
window where than a console.  I understand how complicated you think 
this will be.  But it can be done with C++ just as with just about any 
programming application.

By the way, the program does compile.  I've already started to add the 
gui interface.  I did it with the gtk label with the help of Alan.  I 
posted the example in a different thread.  I ran into problems when I 
tried to change the label widget into a textview widget because I was 
having problems understanding the full gist of the gtkmm tools.  When 
Kjell posted his resolution, I saw the light.  So I started this thread 
on trying to break down Kjell's program into components (namely to 
eliminated the unneeded widgets).

I'm getting there with some of the in-between the line suggestions from 
this new thread.  I'm starting to understand more and more how to use 
gtkmm, of which I'm trying to do.  I really don't think it's as 
complicated and some users are suggesting.  I believe it's just a matter 
of getting a grip of a few vague concepts.

While I'm having problems just sending text to a window, you're 
suggesting that I dive figure and use gtkmm for my other calls.  I might 
get to that at some time.  But at present, I just want to use gtkmm to 
output to a gui screen instead of a black screen.

-- L. James

--
L. D. James
ljames apollo3 com
www.apollo3.com/~ljames