evtest(1)
NAME
evtest - Input device event monitor and query tool
SYNOPSIS
evtest [--grab] /dev/input/eventX
evtest --query /dev/input/eventX <type> <value>
DESCRIPTION
The first invocation type displayed above ("capture mode") causes
evtest to display information about the specified input device,
including all the events supported by the device. It then monitors the
device and displays all the events layer events generated.
If the --grab flag is given in capture mode, evtest keeps an EVIOCGRAB
on the device. While this grab is active, other processes will not
receive events from the kernel devices. The grab is released again when
evtest quits.
In the second invocation type ("query mode"), evtest performs a
one-shot query of the state of a specific key value of an event type.
type is one of: EV_KEY, EV_SW, EV_SND, EV_LED (or the numerical value)
value can be either a decimal representation (e.g. 44), hex (e.g.
0x2c), or the constant name (e.g. KEY_Z) of the key/switch/sound/LED
being queried.
If the state bit is set (key pressed, switch on, ...), evtest exits
with code 10. If the state bit is unset (key depressed, switch off,
...), evtest exits with code 0. No other output is generated.
evtest needs to be able to read from the device; in most cases this
means it must be run as root.
evtest is commonly used to debug issues with input devices in X.Org.
The output of evtest shows the information presented by the kernel;
based on this information it can be determined whether a bug may be a
kernel or an X.Org issue.
DIAGNOSTICS
If evtest does not show any events even though the device is being
used, the device may be grabbed by a process (EVIOCGRAB). This is
usually the case when debugging a synaptics device from within X. VT
switching to a TTY or shutting down the X server terminates this grab
and synaptics devices can be debugged.
The following command shows the processes with an open file descriptor
on the device:
fuser -v /dev/input/eventX
EXIT CODE
evtest returns 1 on error.
When used to query state, evtest returns 0 if the state bit is unset
and 10 if the state bit is set.
SEE ALSO
inputattach(1)
AUTHOR
evtest was written by Vojtech Pavlik <vojtech@suse.cz[1]>.
This manual page was written by Stephen Kitt <steve@sk2.org[2]>, based
on that present in the lineakd package, for the Debian GNU/Linux system
(but may be used by others).
NOTES
1. vojtech@suse.cz
mailto:vojtech@suse.cz
2. steve@sk2.org
mailto:steve@sk2.org
07/25/2015 EVTEST(1)
Free and Open Source Software