Bash - Convert String to Number and Store in Variable

Question

I am trying to store CPU temperature in a variable. I am not sure how to use sed so I am mostly using grep. Here is what I have tried so far, but I am getting syntax error. I am also getting error during the comparison, but I thing it is because CPUTEMP is not resolving.

#!/bin/bash
#
CPUTEMP = $((/usr/bin/sensors k10temp-pci-00c3 | grep temp1 | awk '{print \$2}' | grep -o '[0-9,.]\+'))

if [ "$CPUTEMP" -le 40 ]; then
    echo "OK - CPU idle"
    exit 0
...
...
fi

What am I doing wrong here? Thank you!

Though I suspect http://mywiki.wooledge.org/BashFAQ/022 might be helpful. — Shawn, Jul 13 '23 at 03:38
`$(( ... ))` is for arithmetic evaluation, whereas `$( ... )` is for command substitution. — Grobu, Jul 13 '23 at 04:45
@jared_mamrot : you've already double-quoted the shell variable `$CPUTEMP` so i'm guessing the `print \$2` can be changed to just `print $2` ? — RARE Kpop Manifesto, Jul 13 '23 at 04:48
@jared_mamrot : oh hehehe the alpha char class needs to be symmetrical =p — RARE Kpop Manifesto, Jul 13 '23 at 09:28
Another mistake! This is why we need example input/output to test potential solutions :) — jared_mamrot, Jul 13 '23 at 09:33
I have tried changing to CPUTEMP = $(/usr/bin/sensors k10temp-pci-00c3 | grep temp1 | awk '{print $2}' | grep -o '[0-9,.]\+') but I see CPUTEMP: command not found when I run the script file. — Amar, Jul 13 '23 at 13:20
In my script file I had CPUTEMP = .... Note the space before and after =. That was the issue. There shouldn't be any space before and after =. Thank you for your help guys. — Amar, Jul 13 '23 at 13:27

score 0 · Accepted Answer · answered Jul 13 '23 at 14:59

I read some more online and was able to solve my problem. There were four problems in my script.

I used $(( ... )) instead of $( ... )
There were spaces before and after =
No need for \ before $2

(all of these problems above are in the same line where CPUTEMP is assigned a value)

Bash can only compare integers, but my CPUTEMP variable contains floating point number. Need bc for the workaround.

Here is the working code:

#!/bin/bash
#
CPUTEMP=$(/usr/bin/sensors k10temp-pci-00c3 | grep temp1 | awk '{print $2}' | grep -o '[0-9,.]\+')

if (( $(echo "$CPUTEMP <= 40" | bc -l) ))
then
    echo "OK - CPU idle"
    exit 0
...
...
fi

Thank you for your help guys!

Bash - Convert String to Number and Store in Variable

1 Answers1