ctrlw

Mouse button 4 (BTN_SIDE) sends Ctrl+W to the active window. Works on Wayland and X11 — no X dependency: it reads evdev input devices and emits keys through a uinput virtual keyboard.

Build

Requires libevdev-devel (Fedora: sudo dnf install libevdev-devel).

make

Compiles ctrlw.c → ctrlw in this directory.

Make reference

Target	Effect
make / make all	build ./ctrlw
make check	valgrind leak check + ASan memory-error smoke test
make install	setgid install of the binary + man page — run as: sudo make install
make uninstall	remove the installed binary and man page
make tldr-install	install the tldr page to the user tldr cache (no root)
make clean	remove build artifacts
make help	show all targets

Overridable variables:

Variable	Default	Meaning
CC	gcc	compiler
CFLAGS	-O2 -Wall -Wextra	extra compiler flags, e.g. make CFLAGS='-O0 -g' for a debug build
PREFIX	/usr/local	install prefix
BINDIR	$(PREFIX)/bin	install directory
MANDIR	$(PREFIX)/share/man/man1	man page install directory
TLDIR	$(HOME)/.local/share/tldr/pages/linux	tldr page install directory
GROUP	input	setgid group of the installed binary
DESTDIR	(empty)	staging root for installs, e.g. make install DESTDIR=/tmp/stage

Testing

make check

Runs the program under valgrind (full leak check, 10 s) and an AddressSanitizer build (memory errors, 5 s). Fails the check if there are leaks or errors. Missing tools are reported with the install command:

sudo dnf install valgrind libasan    # Fedora

make check binds the real mice when your user is in the input group (sg), otherwise it runs without device access and says so.

Permissions

/dev/input/event* and /dev/uinput are root:input 0660. Either add your user to the input group (needs re-login), or use a setgid install — preferred, works for everyone with no group membership:

sudo make install

(same as: sudo install -m 2755 -g input ctrlw /usr/local/bin/ctrlw)

Re-run after every recompile: install copies the new build over the old one (keeping the setgid bit and input group). Remove with sudo make uninstall.

Run

ctrlw                  # installed setgid binary — no group needed
./ctrlw-run            # workspace build, adds the input group via sg (no re-login)
./ctrlw                # workspace build, needs input group (current session: re-login)
ctrlw --help           # short usage, from the binary
man ctrlw              # full manual page (after make install)
tldr ctrlw             # tldr page (after: sudo dnf install tealdeer, make tldr-install)

Stop with Ctrl+C; the virtual keyboard is removed automatically.

Behavior

• Binds every mouse that exposes BTN_SIDE (button 4), so the binding works whichever mouse is used.
• On press sends: Ctrl down, W down, W up, Ctrl up.

Files

• ctrlw.c — source (poll(2) loop + uinput; no X11)
• Makefile — build/install: make, sudo make install, make check
• check.sh — the make check leak/memory test runner
• man/ctrlw.1 — manual page (installed by make install)
• tldr/ctrlw.md — tldr page (installed by make tldr-install)
• ctrlw-run — wrapper that adds the input group via sg

Notes

• If you remap the side buttons in input-remapper presets, those presses are consumed there and never reach ctrlw.

License

MIT