Getting a Bash variable into GTK3

ab1jx · 01-01-2022, 09:40 PM

Bash variables are loosely typed, sorta like javascript. GTK3 (well, c) uses actual types like int, char[]. Now suppose I'm writing a program where I want to display the computer's IP address in a GTK_LABEL, but actually the address comes out of something like

Code:

myip=$(dig +short myip.opendns.com @resolver1.opendns.com)

(dig example from the web to read a current IP).

An ip4 IP can be at most 20 chars long but can I use char[21]? How do I get from dig's output to GTK3's input? I can't use system(). Is there a more practical way to read the IP?

Oh wait, I could probably do something like

Code:

rslt=system(somevar=$(dig +short myip.opendns.com @resolver1.opendns.com)

but system only returns an int which had me stumped. Somevar could maybe be a char[21].

NevemTeve · 01-02-2022, 12:30 AM

To get the output of the command, popen(3) might be better than system(3). Then you can use inet_aton(3) or inet_pton(3).

EdGr · 01-02-2022, 10:11 AM

You can use getenv () to read environment variables.
Ed

dugan · 01-02-2022, 10:25 AM

If you're using GTK, wouldn't you call g_spawn_command_line_sync or something similar?

ab1jx · 01-02-2022, 12:19 PM

I'm just barely learning GTK, I don't know about such things yet.

This program:

Code:

#include <stdio.h>
FILE *p;  // pipe

int main(void) {
  p = popen("$(dig +short myip.opendns.com @resolver1.opendns.com)","r");
  if (p) printf("Not null\n");
  pclose(p);
  return 0;
}

Returns:

Code:

./pas
Not null
sh: 1: 172.58.160.58: not found

So the IP gets dumped out on a command line and sh doesn't know why. I guess it's a start.

I want to set up a Raspberry Pi with an 8 inch touch screen display (no mouse or keyboard) as an ad blocking wifi AP fed from a CAT5 internet connection. Right now I have something similar fed by this Pi, which is fed by Easytether and a USB cable from a cell phone. So I want useful stuff on the touchscreen I can read and tap on. I was trying to use Whiptail but I don't think that's going to cut it.

NevemTeve · 01-02-2022, 01:05 PM

It's a good start, here is an improved version:

Code:

#include <arpa/inet.h>
#include <ctype.h>
#include <errno.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>

int main(void) {
  FILE *p;  // pipe
  char strip[32];
  unsigned l;
  struct in_addr ip;

  p = popen("dig +short myip.opendns.com @resolver1.opendns.com","r");
  if (!p) {
     printf("error in popen: errno=%d %s\n", errno, strerror(errno));
     exit(12);
  }
  if (!fgets(strip, sizeof strip, p)) {
     printf("error in fgets: errno=%d %s\n", errno, strerror(errno));
     exit(13);
  }
  pclose(p);

  l= strlen(strip);
  while (l>0 && isspace(strip[l-1])) strip[--l] = '\0';
  printf ("\"%s\"\n", strip);

  if (inet_aton(strip, &ip)!=1) {
     printf("inet_aton(%s) failed\n", strip);
     exit(13);
  }

  printf("ok, IP=%s\n", inet_ntoa(ip));

  return 0;
}

ab1jx · 01-06-2022, 08:18 PM

I'm newish to GTK but I like GTK3. I've done some xlib stuff, and bunches of Borland Delphi in another life. Making a fake GTK form here. I can turn off blocking with symlink games with the hosts file. So there's my real IP at top, beginnings of a button (1 of 2), and 2 labels for (fake) uptime and data age.

EdGr · 01-09-2022, 09:08 AM

Quote:

Originally Posted by ab1jx

I'm newish to GTK but I like GTK3.

I too like GTK 3. It is the best of the GUI toolkits (IMO).

You may want to look into Glade to create complex GUIs.
Ed

ab1jx · 01-09-2022, 09:50 AM

I've used Glade, or tried to. I've been trying since GTK 1 and 2, maybe 20 years, it just never clicked before. Now I can pull out my checklist or an old program I wrote and actually make stuff happen. I do xlib that way now too, there's a set of steps which have to be in the right order with none forgotten. https://sourceforge.net/projects/epidemicsim/

I'd like to see somebody write an unglade which could remove glade's tokens and replace them with straight GTK code so it would compile without libglade. Glade is "cheating" in my book. I haven't tried GTK4 yet.

EdGr · 01-09-2022, 12:22 PM

Libglade has been replaced by GtkBuilder. GTK 3 reads the Glade XML files directly.

Calling GTK to set up widgets becomes unwieldly after more than a half-dozen or so. On complex GUIs, Glade can be a significant time-saver.
Ed

ab1jx · 01-09-2022, 12:29 PM

What it looks like so far.

Semi-related question: I make my 2 pushbuttons for blocking on and off with gtk_button_new_with_label(). I use signal_connect_swapped and write callbacks which I can trigger when they're clicked. But I want to change some colors on the faces of the buttons to show the state of the blocking. I can send markup to them except I need a handle or pointer or something that refers to the labels in the buttons.

Just tried

Code:

onLabel = btn_on->get_child();

but ‘GtkWidget’ {aka ‘struct _GtkWidget’} has no member named ‘get_child’

EdGr · 01-09-2022, 12:35 PM

Are you using the C API? You can change the label by calling gtk_button_set_label ().
Ed

ab1jx · 01-10-2022, 03:16 PM

Hmm, it's not so much changing the label I want as having a cursor, something that indicates which item is selected. I don't see a reasonable way to change the markup, I was going to change the text color on the selected item. I suppose I could add an * or something to the selected one and take it away again. (Blocking on/Blocking off buttons). I'm looking at Devhelp for info. Maybe there's a way to change the markup but it belongs to the label that's on the button, I don't see anything under gtk_button that looks right.

EdGr · 01-10-2022, 06:20 PM

You want a GtkCheckButton.
Ed

ab1jx · 01-11-2022, 02:30 PM

I'm so far sticking with my original idea of changing the text color by changing markup. I do

Code:

list1 = gtk_container_get_children(GTK_CONTAINER(btn_off));
gtk_label_set_markup(GTK_LABEL(list1->data),markup1);

Which sort of works, except the way I'm getting a handle/pointer/whatever for the labels on the buttons is by doing gtk_container_get_children. This is clumsy if there's more than one child, you'd really want more like list1->data[0] which doesn't work. Get_children returns a glist but how do you move around the list? I was using list1, markup1, etc. expecting a list for each button.

Code:

  char *format1;
  char *format2;
  gchar *markup1;
  gchar *markup2;
  format1 = "<span foreground=\"#000000\">%s</span>"; // black
  format2 = "<span foreground=\"#00ff00\">%s</span>"; // green
  markup1 = g_markup_printf_escaped(format1,"Blocking Off");
  markup2 = g_markup_printf_escaped(format2,"Blocking On");
  gtk_label_set_markup(GTK_LABEL(list2->data),markup2);

It works until I try to subscript the list, then it segfaults when I click my buttons.