Search code examples
bashfreebsdbeep

Bash script to beep when temperature hot on FreeBSD

I have been working on a Bash script to beep when the PC is too hot. I have removed the beep to try identifying the problem. What I have so far:

temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
echo $temp

if ["$temp" -gt "30.1"]
then
   echo "temp hot"
else
   echo "temp ok"
fi

My output is

54.1
temp.sh: line 4: [54.1: command not found
temp ok

Removing the if statement just outputs

54.1

so I think it's the if statement that's not working.

Solution

  • You should use double parenthesis (( )) to do arithmetic expressions, and since Bash cannot handle decimal values, you just have to remove the dot (as if you want to multiply it by ten).

    temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
max_temp=50.2

(( ${temp//./} > ${max_temp//./} )) && echo "temp hot" || echo "temp ok"

    Be sure to use the same format for both values (especially leading zeros, 54.10 would become 5410).

    If the format cannot be guaranteed, there is a second method, as mentioned by Benjamin W, using bc. You can send to this command a logical operation involving floats, it returns 0 if true, 1 otherwise.

    temp=$(sysctl -n hw.acpi.thermal.tz0.temperature | tr -d 'C')
max_temp=50.2

(( $(echo "$temp > $max_temp" | bc) )) && echo "temp hot" || echo "temp ok"