CODEWITHSUNDEEP
bashshellmath
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Admin YaCart.com

Reputation: 9

Bash/Shell Script - arithmetic operator failing

I'm trying to slow down my infinite loop if CPU load exceeds certain limit, but, its just not working out right, below is the code. The if condition always results true

c=1
while [ $c -le 1 ]
do
#echo "Welcome $c times"
#php BALHABLH.php

IN=$(cat /proc/loadavg);

set -- "$IN"
IFS=" "; declare -a Array=($*)
echo "${Array[@]}"
echo "${Array[0]}"
echo "${Array[1]}"

#var = ${Array[1]}



x=$(expr "${Array[1]}" )

if [ $x > 0.91 ]
then
    echo "CPU LOAD > 0.91"
    sleep 2
fi


(( c++ ))
done

Upvotes: 0

Views: 1171

Answers (3)

user000001
user000001

Reputation: 33327

Bash only handles integers. To handle floats pipe to bc like this:

[ $(echo " $x > 0.91" | bc -l) -eq 1 ]

bc returns 1 if the comparison is true. We compare with 1 (using the -eq operator).

Validation

$ cat test.sh
#!/bin/bash  
x="$1"
if [ $(echo " $x > 0.91" | bc -l) -eq 1 ]; then
   echo greater;
else 
   echo smaller;
fi
$ ./test.sh 0.5
smaller
$ ./test.sh 1.5
greater

You can also simplify your script a bit like this:

#!/bin/bash
c=10
for (( i=1;i<=c;i++ )); do
    load=$(awk '{print $2}' /proc/loadavg)
    echo "$i: load is $load"
    if (( $(echo "$load > 0.91" | bc) == 1 )); then
        echo "CPU LOAD > 0.91"       
        sleep 2
    fi
done

Upvotes: 0

Scrutinizer
Scrutinizer

Reputation: 9926

Bash cannot use floating point arithmetic. You could do something like this:

if [ $( echo "$x > 0.91" | bc ) -eq 1 ]; then

Upvotes: 0

dogbane
dogbane

Reputation: 274592

You need to use bc for floating point comparison and use (( ... )) for arithmetic expressions:

if (( $(bc -l <<< "$x > 0.91") == 1 ))

Also don't use cat, use:

IN=$(</proc/loadavg)

Upvotes: 2

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