Integer expression expected (Bash)

Question

I'm trying to create a simple script that checks if the CPU Usage is at a certain level. I have a Raspberry Pi for this project.

The only issue I have currently is that I have the variable CPU which is the CPU usage, when the script runs, I get the error

line 25: [: 4.8: integer expression expected

I'm not sure why bash returns this if BASH really doesn't care about int, String, etc. like JAVA does. Found that out here.

Also, I have the if statement: if $CPU -gt 1 only for testing (it's supposed to return true right now)

red='\e[0;31m'
yellow='\e[1;33m'
NC='\e[0m' # No Color
echo -e "${NC}Starting Server!${NC}"
echo -e "${red}Errors in red!${NC}"
echo -e "${yellow}Info in yellow!${NC}"
sleep 1
echo -e "\n\n"
##CPU USAGE STUFF
echo -e "${yellow}Current CPU Usage:"
CPU=$(top -bn1 | grep "Cpu(s)" | \
           sed "s/.*, *\([0-9.]*\)%* id.*/\1/" | \
           awk '{print 100 - $1""}')
echo $CPU %
echo -e "${NC}**********${NC}"
cd /root/mc_server/
sleep 1


##CPU USAGE LOOP CHECKER
while :
do
        sleep 5
        echo $CPU
        if [ $CPU -gt 1 ]
        then
        echo -e "${red}ALERT! CPU Usage is TOO HIGH!${red}"
        fi

done
##


##java -Xmx400M -jar bukkit.jar -o true

integer means integer. If you pass bash a value like 4.8 then it starts wondering if it needs to look for an exponent value, ie. 4.800889e27, and that would be a lot of work ;-). Just round your 4.8 value or truncate it and then you'll have an integer value that will work. case $CPU in *\.* ) CPU=${CPU%%.*} ;; esac might help. Good luck. — shellter
– shellter, Commented Sep 1, 2014 at 19:55
@Olivr3000 as shelter says, simply take the whole-number from $CPU. The most efficient way is to remove everything up to and including the decimal beginning at the right with substring extraction. CPU=${CPU%.*} %% works, the only difference being it say remove all occurrences of . beginning at the right, compared to % which is first occurrence. — David C. Rankin
– David C. Rankin, Commented Sep 1, 2014 at 20:12

ShaneQful · Accepted Answer · 2014-09-01 19:59:25Z

4

The issue is that 4.8 is an non-integer value.

You can use bc to deal with non-integer values like so:

if [[ $(echo "$CPU > 1" | bc -l) -eq 1 ]];

it will return boolean expressions as either 1 for true or 0 for false.

answered Sep 1, 2014 at 19:59

ShaneQful

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