Bash Script with IF Conditions for Numbers with Comma - bash

Question

i'm new into bash scripts and i really need your help.
The following Script gets humidity and temperature from a DHT22 sensor on my BananaPi and sends it to my HomeAutomation.
#!/bin/bash
cd /opt/lol_dht22
WERTE=$(./loldht 7 | grep "Humidity")
Temp=( $(echo $WERTE | awk '{ print $ 7}'))
Hum=( $(echo $WERTE | awk '{ print $ 3}'))
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 temperature $Temp"
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 humidity $Hum"
The results are like 30.00 (With a Comma), and sometimes the sensor fails and gives an unrealistic value like -3000.00 or similar.
So i wanted to implement a IF Condition which checks if it's greater or equal 0 or less or equal 100.
I tried things like:
#!/bin/bash
cd /opt/lol_dht22
WERTE=$(./loldht 7 | grep "Humidity")
Temp=( $(echo $WERTE | awk '{ print $ 7}' | tr '.' ','))
Hum=( $(echo $WERTE | awk '{ print $ 3}' | tr '.' ','))
if [[ $Temp -ge 0 && $Temp -le 100 && $Hum -ge 0 && $Hum -le 100 ]]; then
Temp1=( $(echo $Temp | tr ',' '.'))
Hum1=( $(echo $Hum | tr ',' '.'))
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 temperature $Temp1"
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 humidity $Hum1"
else
exit;
fi
It seemed like the comma (.) was the problem, so i tried switching it to a (,) and back. But there are sometimes still values which are not between 0 and 100.
I hope someone can help me,
thank you!
Regards,
Klaus

Answer 1

awk uses doubles, and can easily be used to test the range of decimal numbers.
...
Temp=$(echo $WERTE | tr , . | awk '$7>=0&&$7<=100{print$7}')
Hum=$(echo $WERTE | tr , . | awk '$3>=0&&$3<=100{print$3}')
if [ -n "$Temp" -a -n "$Hum" ]; then
...
fi

Answer 2

-lt, -ge, etc. only work with integers. You can use <, >=, etc. inside [[, and it should work on floating point numbers too.
Some good practices in bash:
#!/bin/bash
set -e #autoexit if you run into an error
cd /opt/lol_dht22
#Reserve all-caps variables for exported variables and bash config variables
werte="$(./loldht 7 | grep "Humidity")" #always double-quote $ expressions
#foo=( bar ) creates arrays, you don't want that
#printf "%s\n" is more robust than echo if you're printing the contents of variables
Temp="$(printf '%s\n' "$werte" | awk '{ print $7 }' | tr . ,)"
Hum="$(printf '%s\n' "$werte" | awk '{ print $3 }' | tr . ,)"
#-lt etc. only work with integers
if [[ "$Temp" >= 0 && "$Temp" < 100 && "$Hum" >= 0 && "$Hum" < 100 ]]; then
Temp1="$(printf '%s\n' "$Temp" | tr , .)"
Hum1="$(printf '%s\n' "$Hum" | tr , .)"
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 temperature $Temp1"
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 humidity $Hum1"
else
exit 1 #return nonzero codes for errors
fi

Answer 3

Please mention what is content of WERTE. It will help in answering the question because awk FS by default is space. We need to properly understand your content of $7 and $3

Answer 4

Thank your Guys,
i've learned a lot.
and it seems to work:
#!/bin/bash
set -e
cd /opt/lol_dht22
WERTE=$(./loldht 7 | grep "Humidity")
Temp=$(echo $WERTE | awk '$7>=0&&$7<=100{print$7}')
Hum=$(echo $WERTE | awk '$3>=0&&$3<=100{print$3}')
if [ -n "$Temp" -a -n "$Hum" ]; then
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 temperature $Temp"
perl /opt/fhem/fhem.pl 7072 "setreading DHT22 humidity $Hum"
else
exit 1
fi
You've saved my Sunday =)
Best Regards,
Klaus