Re: Calling system() from a GTK+ callback

[Gary Wong <gtw research att com>]

"David C. Hoos, Sr." <david c hoos sr ada95 com> writes:
> I am trying to issue a call of the form
>
>   system ("/usr/bin/rsh some-host 'some-command with arguments' > 
>       <some-file-on-remote-host &");

Note that if you want the redirection to occur on the remote host, you
should quote the redirection, as well (i.e. "rsh host 'cmd > foo' &", not
"rsh host 'cmd' > foo &".  But that's an rsh issue, not a GTK one.

> The command works when issued from a simple C program (not a GTK+
> program), but the call "hangs" if made from a GTK+ callback function.

I am unable to duplicate the problem.  The following test code appears to
work for me (using either system() or fork()/exec()).  Note that the style
is poor (it doesn't check return codes of system calls, nor clean up its
zombies) but those things should be irrelevant to any GTK problems.

Does my code work on your system?  If so, are you able to send me a small
section of your code which does not work, or modify my example to
demonstrate the problem?

Cheers,
Gary.

---------- example code follows:
/*
 * example of system() or fork()/exec() in a GTK+ callback
 *
 *    compile with "cc -o foo `gtk-config --libs --cflags` foo.c"
 */
#include <gtk/gtk.h>

static void callback( GtkWidget *widget, gpointer data ) {

#if 0
    system( "rsh other-host 'date >> /tmp/abc' &" );
#else
    if( !fork() ) {
        execlp( "rsh", "rsh", "other-host", "date >> /tmp/abc", NULL );
        _exit( 1 );
    }
#endif
}

int main( int argc, char *argv[] ) {

    GtkWidget *window;
    GtkWidget *button;
    GtkWidget *box1;

    gtk_init (&argc, &argv);
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_signal_connect (GTK_OBJECT (window), "delete_event",
                        GTK_SIGNAL_FUNC (gtk_main_quit), NULL);
    box1 = gtk_hbox_new(FALSE, 0);
    gtk_container_add (GTK_CONTAINER (window), box1);
    button = gtk_button_new_with_label ("rsh");
    gtk_signal_connect (GTK_OBJECT (button), "clicked",
                        GTK_SIGNAL_FUNC (callback), NULL);
    gtk_box_pack_start(GTK_BOX(box1), button, TRUE, TRUE, 20);
    gtk_widget_show_all(window);
    gtk_main ();
    return(0);
}
-- 
  Gary Wong    Consultant, Dependable Distributed Computing, AT&T Shannon Labs
        gtw research att com            http://www.cs.arizona.edu/~gary/