Calculate the average size and compression ratio for rotated logfiles

average.sh

#!/bin/bash

[[ -z "$1" ]] && exit 1

float_div ()  # Arguments: dividend and divisor
{
    if [ $2 -eq 0 ]; then echo division by 0; exit; fi
    local p=12                            # precision
    local c=${c:-0}                       # precision counter
    local d=.                             # decimal separator
    local r=$(($1/$2)); echo -n $r        # result of division
    local m=$(($r*$2))
    [ $c -eq 0 ] && [ $m -ne $1 ] && echo -n $d
    [ $1 -eq $m ] || [ $c -eq $p ] && return
    local e=$(($1-$m))
    c=$(($c+1))
    float_div $(($e*10)) $2
}

log_dir=$1
log_files="access.*"

mkdir -p $log_dir/tmp

cp $log_dir/$log_files.gz $log_dir/tmp
compressed_average=`ls -l $log_dir/tmp/$log_files.gz | awk '{sum += $5; n++;} END {printf "%d", sum/n;}'`

gunzip $log_dir/tmp/$log_files.gz
raw_average=`ls -l $log_dir/tmp/$log_files | awk '{sum += $5; n++;} END {printf "%d", sum/n;}'`

rm -rf $log_dir/tmp

pushd $log_dir > /dev/null && echo $(pwd)/${log_files::-1}log && popd > /dev/null
printf "Average raw size in bytes: %d\n" $raw_average
printf "Average compressed in bytes: %d\n" $compressed_average
#printf "Average raw size in GB: %.12f\n" $(float_div $raw_average $((1024*1024*1024)))
#printf "Average compressed in GB: %.12f\n" $(float_div $compressed_average $((1024*1024*1024)))
printf "Average compression ratio is %d:1\n" $(( $raw_average / $compressed_average ))