Print a matched group from a file using sed

sed_print_matched_group.sh

cat graylog-search-result-relative-604800.csv | while read line
do 
    echo $line | sed -n -r 's/.*db":([0-9]*\.[0-9]*).*/\1/p' 
done


cat graylog-search-result-keyword-since-april3.csv | while read line
do 
    echo $line | sed -n -r 's/.*email":"([A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,})",.*/\1/pi'
done 

let linenum=1
cat graylog-slow-query.csv | while read line
do   
    let linenum=linenum+1
    echo "`echo $line | sed -n -r 's/.*\(([0-9]*\.[0-9]*ms)\).*/\1/p'` || $linenum" 
done
# use it
let linenum=1
export wecare=(12 194 195 1109 1692 1885 1906 2204)
cat graylog-admin-api-5min.csv | while read line
do
    let linenum=linenum+1
    for i in ${wecare[@]}; do
        if [ $i == $linenum ] 
        then
            echo $line
        fi
    done

done