Arithmetic expression error in shell scripting

Question

First i will take value of yesterday & Today file size in bytes (a=yesterday & b=today)

I need to calculate the percentage and find out if difference greater than or less than 10%

a=21007558 -- Yesterday
b=19330    -- Today 

c=`expr ((($b/$a) "*" 100) "-" 100) | bc`

This is not working

Note that, if this is your actual code, the variables a and b will be empty: -- is not the shell's comment mechanism. You'll see this error: bash: --: command not found. I can explain further if requested. — glenn jackman
– glenn jackman, Commented Aug 26, 2016 at 13:17

Mustafa DOGRU · Accepted Answer · 2016-08-26 08:54:39Z

2

you can use scale option as below;

c=$(echo "scale=6;((($b/$a) * 100) -100)" | bc)
echo $c

to lest than or greter than %10; you can try as below;

let c=$(echo $(printf %.$2f $(echo "scale=6;((($b/$a) * 100) -100)" | bc)))
if [[ c -lt -10  ]]; then
echo "decrease rate is %"$c    
fi
if [[ c -gt 10  ]]; then
echo "increase rate is %"$c    
fi

edited Aug 26, 2016 at 8:54

answered Aug 26, 2016 at 8:22

Mustafa DOGRU

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1 Comment

Mustafa DOGRU Over a year ago

@senthil; I update ans. added if statement < or > 10%

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