How to detect file content changes using Gio

Platform
1

How can I detect file content changes or file modification using Gio? I’m trying to monitor changes in /sys/class/backlight/amdgpu_bl1/brightness file so that I can update the brightness level in my bar. So far I’ve tried this one but the handler never invokes when I change brightness with brightnessctl

screen_path = "/sys/class/backlight/amdgpu_bl1/brightness"
file = Gio.File.new_for_path(screen_path)
file_mon = file.monitor(Gio.FileMonitorFlags.NONE)

def screen_file_handler: print("brightness changed")

file_monitor.connect("changed", screen_file_handler)
2

sysfs doesn’t support inotify (et al.), so GFileMonitor won’t work.

You can look at how gnome-settings-daemon does this using udev uevents: plugins/power/gsd-backlight.c · master · GNOME / gnome-settings-daemon · GitLab

Alternatively, I believe you can just poll the file.

2 Likes
3

Yeah alternatively I can use python watchdog in that case. I guess FileMonitor only detects rename, move events etc.

4

Hi,

Can you try monitor_file? it works on my side (on standard files).

file_mon = file.monitor_file(Gio.FileMonitorFlags.NONE, None)

Note that some filesystems don’t properly notify Gio about file changes, it’s e.g. the case of the FUSE filesystem used by flatpak’s document portal. Maybe /sys is affected too?

1 Like
5

Try

def on_f_changed(file_monitor,g_file,other_file,event_type):
    if event_type == Gio.FileMonitorEvent.CHANGES_DONE_HINT:
        print("done")

g_file        =  Gio.File.new_for_path("/sys/class/backlight/amdgpu_bl1/brightness")
file_monitor  =  g_file.monitor_file(Gio.FileMonitorFlags.NONE)
file_monitor.set_rate_limit(800)
file_monitor.connect("changed",on_f_changed)

Gtk3 Example

1 Like
6

It works and so my previous solution. I’ve a project structure like this:

/home/xt/oniui
├── __init__.py
├── app.py
├── < more stuffs >
╰── Services
.....├── __init__.py
.....╰── Brightness.py

For some odd reason it works in app.py:

path = "/system/class/backlight/amdgpu_bl1/brightness"

file = Gio.File.new_for_path(screen_path)
file_mon = file.monitor_file(Gio.FileMonitorFlags.NONE, None)

def handler(*args): 
    print("changed")

file_mon.connect("changed", handler)

But when I do the same inside __init__ in Brightness.py and then import in app.py

from oniui.Services.Brightness import Brightness

brt = Brightness()

It doesn’t work

7

It does work if I put it inside app.py. But if I put the same code inside ./Services/Brightness.py and then import it then it doesn’t :slightly_frowning_face:

8

Could it be that you need to start the glib mainloop (e.g. by running the application) before creating the monitoring?

9

Maybe I guess. I got it working anyway using AstalIO from libastal (from the creator of Aylur’s Gtk Shell)

10

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