Sin

🙏 Forgive me father for I have simply inhibited.

Simple Inhibitor (Sin) watches /proc for processes matching your patterns and inhibits system idle/sleep while they run.

Why

Your system shouldn't sleep while you're watching a movie, compiling code, or running a long task. Sin prevents that by talking to systemd-logind when your processes are active.

I think this is should be a part of the idle program itself, but I could not find an idle daemon that supports this feature. Naturally I made one of my own. You are welcome to use it if this fits your needs. It is easy to Simply Inhibit.

This is an alternative to handling inhbiting on a compositor level, and is aimed to detect things a compositor generally cannot. In the case of, e.g., desktop applications I recommend letting your compositor handling the inhibit. I might also support this for Sin in the future.

How it works

1. You tell Sin which processes to watch (e.g., mpv, steam, ffmpeg)
2. Sin scans /proc every few seconds looking for them
3. When found, it grabs a Systemd inhibitor lock
4. When they exit, it releases the lock
5. Your system can sleep again

Great success!

Usage

# Keep system awake while Firefox is running
sin -n firefox

# Watch multiple processes
sin -n steam -n "wine " -n lutris

# Prevent sleep (not just idle) while rendering
sin -n blender --what=sleep

# Custom poll interval
sin -n mpv --poll=1.0

Options

-n, --name PATTERN     Process cmdline substring to watch (required, repeatable)
--what WHAT           What to inhibit: idle, sleep, shutdown, etc. (default: idle)
--mode MODE           block or delay (default: block)
--poll SECONDS        How often to check (0.1-3600, default: 2.0)
-d, --daemon          Run as daemon (fork to background)
-q, --quiet           Suppress informational output
-v, --version         Show version
-h, --help            Show help

Building

make
sudo make install

Requires:

• GCC or Clang
• libsystemd

That's it.

Examples

# Don't idle while gaming
sin -n steam -n wine

# Keep system awake during long builds
sin -n "cargo build" -n "nix build"

# Prevent sleep while watching videos
sin -n mpv -n vlc --what=sleep

# Fast polling for responsive tasks
sin -n ffmpeg --poll=0.5

# Run as daemon
sin -d -n mpv -n vlc

Running as a Service

A systemd service file is provided in vendor/sin.service. Edit it to match your needs:

# Copy and customize the service file
sudo cp vendor/sin.service /etc/systemd/system/
sudo nano /etc/systemd/system/sin.service  # Edit the ExecStart line

# Enable and start
sudo systemctl enable --now sin.service

Why not just use...?

Systemd-inhibit

There are a few alternative options that you could go with. Namely, Sin is inspired by the operating principle of systemd-inhibit among those options, but prefers an approach similar to EarlyOOM where you provide the programs that you want to watch instead of launching the program with a systemd-inhibit wrapper.

Caffeine

While researching, I've noticed programs such as caffeine and caffeine-ng but ultimately decided against those since they seem to be hooking up to more specific APIs than Systemd's own. I also find Python to be unsuitable for production, and have elected to use C for a smaller and faster binary that is easier to bootstrap.

If you do use those tools, and would like to try out Sin but cannot make a switch due to missing features, please do create an issue. While I do not wish to support screenlocker-specific APIs, I am happy to implement more generic features such as a tray icon. Maybe even support for other init systems in the future.

Hand-written Systemd Service

Sure, if you'd like to write one yourself. Sin is that Systemd service in my case. Give it a try, maybe I've saved you from some code spent fixing a trivial problem.

Attributions

This project was inspired partially by Diniamo's Wayhibit, which deserves the primary attribution here. I'd also like to thank Systemd developers for systemd-inhibit, which has inspired me to write this project and also for the sd-bus API that makes Sin possible.

License

This project is made available under European Union Public Licence (EUPL) version 1.2. See LICENSE for more details on the exact conditions. An online copy is provided here.