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.\"     Title: evtest
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 07/03/2024
.\"    Manual: \ \&
.\"    Source: \ \&
.\"  Language: English
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.TH "EVTEST" "1" "07/03/2024" "\ \&" "\ \&"
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.SH "NAME"
evtest \- Input device event monitor and query tool
.SH "SYNOPSIS"
.sp
.nf
evtest [\-\-grab] /dev/input/eventX
.fi
.sp
.nf
evtest \-\-query /dev/input/eventX <type> <value>
.fi
.SH "DESCRIPTION"
.sp
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\&.
.sp
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\&.
.sp
In the second invocation type ("query mode"), evtest performs a one\-shot query of the state of a specific key \fBvalue\fR of an event \fBtype\fR\&.
.sp
\fBtype\fR is one of: \fBEV_KEY\fR, \fBEV_SW\fR, \fBEV_SND\fR, \fBEV_LED\fR (or the numerical value)
.sp
\fBvalue\fR 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\&.
.sp
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\&.
.sp
evtest needs to be able to read from the device; in most cases this means it must be run as root\&.
.sp
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\&.
.SH "DIAGNOSTICS"
.sp
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\&.
.sp
The following command shows the processes with an open file descriptor on the device:
.sp
.if n \{\
.RS 4
.\}
.nf
fuser \-v /dev/input/eventX
.fi
.if n \{\
.RE
.\}
.SH "EXIT CODE"
.sp
evtest returns 1 on error\&.
.sp
When used to query state, evtest returns 0 if the state bit is unset and 10 if the state bit is set\&.
.SH "SEE ALSO"
.sp
inputattach(1)
.SH "AUTHOR"
.sp
evtest was written by Vojtech Pavlik <\m[blue]\fBvojtech@suse\&.cz\fR\m[]\&\s-2\u[1]\d\s+2>\&.
.sp
This manual page was written by Stephen Kitt <\m[blue]\fBsteve@sk2\&.org\fR\m[]\&\s-2\u[2]\d\s+2>, based on that present in the lineakd package, for the Debian GNU/Linux system (but may be used by others)\&.
.SH "NOTES"
.IP " 1." 4
vojtech@suse.cz
.RS 4
\%mailto:vojtech@suse.cz
.RE
.IP " 2." 4
steve@sk2.org
.RS 4
\%mailto:steve@sk2.org
.RE