Bash Script with IF Conditions for Numbers with Comma

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

kdhp · Accepted Answer · 2016-01-17 13:42:54Z

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

answered Jan 17, 2016 at 13:42

kdhp

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1 Comment

Klouse Over a year ago

What a smooth way, i love this solution, thank you !

Petr Skocik · Accepted Answer · 2016-01-17 13:34:30Z

0

-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

answered Jan 17, 2016 at 13:34

Petr Skocik

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2 Comments

Klouse Over a year ago

Hi, thanks for your awesome answer, the content of WERTE is for example: "Humidity = 23.30 % Temperature = 20.90 *C" is it needed to switch from . to , and back for => <=?

Petr Skocik Over a year ago

Glad you like it. I missed the tr part. If the ./loldht executables outputs numbers with decimal points (not commas), then you shouldn't be calling tr at all. No English-based computer language wants floats with decimal commas.

Varun · Accepted Answer · 2016-01-17 14:55:27Z

0

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

answered Jan 17, 2016 at 14:55

Varun

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1 Comment

Klouse Over a year ago

Hi, the content of WERTE is: Humidity = 23.30 % Temperature = 20.90 *C

Klouse · Accepted Answer · 2016-01-17 18:35:19Z

0

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

answered Jan 17, 2016 at 18:35

Klouse

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