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# Keyboard Listener (kl)
## Description
`kl` is a lightweight, command-line global keystroke monitoring and echoing tool for GNU/Linux systems.
This tool is compiled directly to native binary with zero runtime dependencies. No Node.js, No Electron, No Python, **written in pure C**.
## Install
You can install it with aur.
```bash
paru -S kl
```
or build from source
```
git clone https://github.com/yingyu5658/keyboard-listener.git
cd keyboard-listener
sudo make install
```
## Usage
`kl` designs to interaction with low-level kernel input events directly via `/dev/input/eventx`. We need to find the keyboard event file.
```bash
λ ~/ ls /dev/input/by-path
pci-0000:00:14.0-usb-0:1:1.0-event-mouse pci-0000:00:14.0-usb-0:9:1.1-event
pci-0000:00:14.0-usb-0:1:1.0-mouse pci-0000:00:14.0-usb-0:9:1.1-event-kbd
pci-0000:00:14.0-usb-0:9:1.0-event-kbd platform-pcspkr-event-spkr
```
Find a file which includes word like "keyboard", "kbd" and so on. For the first time of running `kl`, it will create a config file: `~/.klrc`, here is an example:
```
# kl config file (v0.0.1)
#
# Please see your README for details.
#
# This file was auto-generated because it was missing.
device = /dev/input/by-path/pci-0000:00:14.0-usb-0:9:1.0-event-kbd
time = true
```
then run `sudo kl`:
```
λ ~/ sudo kl
Device: /dev/input/by-path/pci-0000:00:14.0-usb-0:9:1.0-event-kbd
2026-05-17 21:54:22.210831: P
2026-05-17 21:54:22.330827: R
2026-05-17 21:54:22.602797: O
2026-05-17 21:54:22.866822: G
2026-05-17 21:54:22.954814: R
2026-05-17 21:54:23.026817: A
2026-05-17 21:54:23.146814: M
2026-05-17 21:54:23.378821: M
2026-05-17 21:54:23.546794: I
2026-05-17 21:54:23.626831: N
2026-05-17 21:54:23.802818: G
2026-05-17 21:54:23.898808: <SPACE>
2026-05-17 21:54:24.082826: I
2026-05-17 21:54:24.554789: N
2026-05-17 21:54:24.746833: <SPACE>
2026-05-17 21:54:24.890809: P
2026-05-17 21:54:25.066811: U
2026-05-17 21:54:25.170807: R
2026-05-17 21:54:25.210811: E
2026-05-17 21:54:25.570792: <SPACE>
2026-05-17 21:54:25.762816: C
```
You can also disable time echo with `time = false`:
```
λ ~/dev/key-catcher/ main* sudo kl
Device: /dev/input/by-path/pci-0000:00:14.0-usb-0:9:1.0-event-kbd
L
E
S
S
<SPACE>
I
S
<SPACE>
M
O
R
E
.
```
---
## SECURITY & PERMISSIONS
Due to the security model of modern Linux distributions (especially on Wayland/systemd-logind), direct access to these device nodes from an unprivileged GUI session is blocked to prevent unauthorized key logging.
If it can't work properly, add your user to `input` group, and reboot your computer.
```bash
sudo usermod -aG input $USER
```
## Report Bug
Feel free to create an issue or a pull request :)
|
