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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)



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