grep and awk like SQL

easy to understand if map *nix console tools to SQL commands.Its usefull to analyse big files with strict stucture, like logs or dumps.

select * from file where column = "keyword"
cat ./bigfile.log | fgrep "keyword"

select sum(numbers) from file where column = "keyword" 
cat ./bigfile.log | fgrep "keyword" |  awk '{a[$1]+=$2}END{for (i in a){print i,a[i]}}'

select avg(numbers) from file where column = "keyword"
cat ./bigfile.log | fgrep "keyword"  |  awk '{a[$1]["s"]+=$2; a[$1]["c"]+=1;}END{for (i in a){ print i,a[i]["s"]/a[i]["c"]} }'

select count(*) from file group by column
cat ./bigfile.log | perl -pe "s/^(REGEXP_PATTERN).*$/\$1/g"  |  sort | uniq -c

with perl or awk analyzing columns can be extracted from source file for further calculating.

group by date and calculating any speed/avg

for example your log file begin with date: 11:29:37.495 DEBUG - <SOME INFO>
gouping by date can be done by cutting chars from end
seconds: cat ./bigfile.log | cut -c -8  | uniq -c
minutes: cat ./bigfile.log | cut -c -5  | uniq -c

скриптуем математику в bash

юзается так:

$ seq 0 99 | ./test_seq.sh is_prime 

Сам скрипт выглядит так... Для проверки простых чисел используется калькулятор для командной строки o.0

#!/bin/bash

even_counter=$(( 2-$1%2  ))

function is_prime {
    number=
    if(( $1 < 0 )); then
        number=$(($1*-1))
    else
        number=$1
    fi
    if(( $number == 1 || $number == 0)); then
        echo $1
        return
    fi
    # а это строчка проверки числа, простое ли оно...
    result=`seq -s "*" 1 $(($number-1)) | 
sed -r "s/([0-9,\*]+)/(\1+1)%$number/" | bc`
    # перенос строчки чисто чтобы в блог нормально влезло

    #echo "[[$result]] for $number"
    if(( $result == 0 )); then
        echo $1
    fi
}

function is_even {
    if(( $even_counter == 2 )); then
        echo $1
        even_counter=1
    else
        even_counter=$(($even_counter + 1))
    fi
}

function is_not_even {
    if(( $even_counter == 1 )); then
        echo $1
        even_counter=$(($even_counter + 1))
    else
        even_counter=1
    fi
}

echo "filtering by: $1"
for item in $(cat)
do
    # echo "Item: $item"
    cmd="$1 $item"
    eval "$cmd"
    # eval $1
done