124 lines
3.5 KiB
Markdown
124 lines
3.5 KiB
Markdown
# desk-reminder
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Small Linux utility that enforces periodic standing desk adjustments. After 20 minutes
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sitting, the screen is locked until the user switches to standing mode on their adjustable
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standing desk. This works via an ecard reader attached to the back of the computer
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screen and the wall, which allows this program to detect when the user is standing or
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sitting.
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## What It Does
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- Grabs a specific input keyboard device with `EVIOCGRAB`, so key events from that device are hidden from other applications.
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- Reads digit key presses (`0-9`) until `Enter`.
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- Hashes the entered numeric string with SHA-256 and compares the first 8 bytes (as a 64-bit number) against a hardcoded value.
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- If the hash matches, it resets the standing timer, kills `i3lock`, and re-enables keyboards.
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- A background watcher thread checks elapsed time every second.
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- Once elapsed time reaches the configured interval, it disables keyboard devices via `xinput` and starts `i3lock` with a lockscreen image.
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Default interval is 20 minutes.
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## Dependencies
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Build-time:
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- GCC
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- OpenSSL development headers/libraries (`libssl-dev` on Debian/Ubuntu)
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- POSIX threads (`pthread`)
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- Linux input headers (`linux/input.h`)
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Runtime:
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- `xinput`
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- `i3lock`
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- X11 session (because keyboard disabling uses `xinput`)
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- Permission to read the target input device in `/dev/input/by-id/...`
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## Build
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The current `Makefile` does not match the source filename in this repository (`desk-reminder.c`), so compile directly:
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```bash
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gcc -Wall -Wextra -O2 desk-reminder.c -o desk-reminder -lssl -lcrypto -lpthread
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```
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## Configure
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Edit the hardcoded device path in `desk-reminder.c`:
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```c
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const char *dev = "/dev/input/by-id/usb-IC_Reader_IC_Reader_08FF20171101-event-kbd";
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```
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Use one of these to find your device path:
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```bash
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ls -l /dev/input/by-id/
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cat /proc/bus/input/devices
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```
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## Usage
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Run with default interval (20 minutes):
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```bash
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./desk-reminder
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```
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Set interval explicitly:
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```bash
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./desk-reminder -i 20m
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./desk-reminder -i 1200s
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```
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`-i` accepts a positive integer and optional unit suffix:
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- `s` for seconds
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- `m` for minutes (default if no suffix)
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Examples:
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- `-i 30` means 30 minutes
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- `-i 30m` means 30 minutes
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- `-i 45s` means 45 seconds
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## Operational Notes
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- This program grabs the configured device exclusively.
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- When timeout is reached, keyboard devices are disabled using:
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- `xinput --list --short | grep -i keyboard | grep -v XTEST | ... | xinput disable`
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- On successful reset code entry, keyboards are re-enabled with the matching `xinput enable` pipeline.
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- Screen lock image is hardcoded to:
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- `/usr/local/share/lockscreens/standing_gopher.png`
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Ensure this file exists, or adjust the command in source.
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## Safety / Recovery
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- Keep another input method available during testing (for example, a second terminal/TTY).
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- Test with a short interval first (`-i 30s`) to verify behavior.
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- If something goes wrong and keyboards remain disabled, use another session/input device to run:
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```bash
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xinput --list --short | grep -i keyboard | grep -v XTEST | sed -E 's/.*id=([0-9]+).*/\1/' | xargs -r -n1 xinput enable
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pkill i3lock
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```
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## Limitations
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- Linux-only.
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- X11-specific keyboard management (not Wayland-native).
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- Input device path, reset hash target, and lockscreen path are all hardcoded.
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- No systemd service/unit is included in this repository.
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## License
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This project is licensed under the GNU General Public License, version 3.
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See `LICENSE` for the full text.
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