Can't get evtest output into variable

Teufel · 05-03-2013, 07:01 AM

Hi!
I'm trying to read evtest output into variable for next usage (parsing).

Code:

#!/bin/bash
while true; do
EVENT=`evtest /dev/input/event0 | grep "LEFT"`
echo "$EVENT"
done

Code hangs on EVENT=`evtest /dev/input/event0 | grep "LEFT"` command.

if I print the output immediately it works and shows output:

Code:

#!/bin/bash
while true; do
echo evtest /dev/input/event0 | grep "LEFT"
done

How can I get it into variable?
Thanks in advance.

pan64 · 05-03-2013, 07:35 AM

evtest monitors /dev/input/event0, so in the first case it probably never returns. Probably you can try:
EVENT=`evtest /dev/input/event0 | head -1 | grep "LEFT"` or similar, but I'm not really sure about the result. Maybe you should write a small script.
In your second case evtest will not run at all.

Teufel · 05-03-2013, 08:52 AM

thanks for reply!
I tried to use evtest piping with head, but it can give me only the first 'n' lines. But I need the last line of output only. Also I tried to use 'tail' but 'tail' can't read from /dev/input/event0.
Also I tried to use evtest-capture (writes output to file) and read it's output by tail. It works, but I got a huge latency and it totally unuseable.