[Glade-users] Started glade 2 days ago!

[james cameron compaq com (James Cameron)]

Ahmad Al-rasheedan wrote:
> 3) Have a C function 'tail_log_file()' that merely tail -f log_file.
>    Where would one put it provided I need the output be placed in
>    GtkText window on some small UI I am doing just to learn glade.

The way I would do it, to make sure that the UI will always be able to
respond the fastest to either X server events or data from the tail, is
to express an interest in the file descriptor from which the tail data
will arrive, using gtk_input_add_full() ...

FILE *pipe;   /* the pipe to the tail process */
guint input;  /* the input source identifier  */

/* start the tail process, perhaps as a callback on map for GtkText */
initialise() {
  pipe = popen("tail -f log", "r");
  input = gtk_input_add_full(fileno(pipe), GDK_INPUT_READ, reader, NULL,
NULL, NULL);
}

/* process arriving data from the tail */
static void reader (gpointer data, gint source, GdkInputCondition
condition) {
  char buffer[1024], *p;
  p = fgets(buffer, 1024, pipe);
  if (p == NULL) {
    /* process send end of file? */
    gtk_input_remove(input);
  }
  /* add the line of text to the GtkText widget */
  ...
  /* remove an old line if necessary */
  ...
}

However, if your tail_log_file() is implemented in the manner of tail(1)
itself, rather than forking a process to run tail(1), then you need to
adjust your thinking.  tail(1) normally waits for a second or so between
checking the file size.  To do this in GTK, add a timeout during
initialisation that causes your tail_log_file() function to be called. 
So long as the function returns TRUE, it will be rescheduled for another
execution.

gtk_timeout_add(1000, tail_log_file, NULL);

These functions are described by the GTK+ documentation and source code.

-- 
James Cameron                                      (cameron stl dec com)

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