Re: help.....playing a song

[Martyn Russell <martyn imendio com>]

On Wed, 2006-01-18 at 12:35 +0500, Shamaila Khalid wrote:
> hi
>  
> i m a student and i want to play a mp3 file at a button click ...

Hi, 

This isn't the right place to be asking these questions.  This list is
about GTK+.

> i m not understanding how to use the following code ..
> as i m working in glade .

If you want to connect a button click, then I suggested you look at the
gtk-demo that comes with the download of gtk+.

> plz help
>  
>  
> #include<unistd.h>
>  
> gchar *gs_call[3];
> >
> >rc = fork ();
> >     if (rc == -1) {
> >       g_warning ("Can?t fork ()");
> >     } else if (rc == 0) {
> >       gs_call[0] = "mpg123";
> >       gs_call[1] = song_name; 
> >       gs_call[2] = 0;
> >       execvp (gs_call[0], gs_call);
> >   }
>  

You can use the man or info pages to understand this (or perhaps even
google).  But to spare you the time, this is a quick run down of what it
does. 

The 'fork' function:
        fork creates a child process that differs from the parent
        process only in its PID and PPID, and in the fact that resource
        utilizations are set to 0.  File locks and pending signals are
        not inherited.

The 'execvp' function:
        The exec family of functions replaces the current process image
        with a new process image. The functions described in this manual
        page are front-ends for the function execve(2).  (See the manual
        page for execve for detailed information about the replacement
        of the current process.)
        
        The execv and execvp functions provide an array of  pointers  to
        null-terminated strings that represent the argument list
        available to the new program. The first argument, by convention,
        should point to the file name associated with the file being
        executed.  The array of pointers must be terminated by a NULL
        pointer.

So, in short, what happens is, you application creates a child process
and then from that child process, you execute another process (which
happens to be the mpg123 application (which will play mp3s).

Next time, make use of the man pages (with 'man execvp' or 'man fork')
to find out the information above before writing to a list about
something off topic.  If you still have questions about how to hook this
up to a button with GTK+, I or anyone here would be happy to help.

-- 
Regards,
Martyn