shell求質數

shell求質數，很多人面試的時候會遇到

 

#!/bin/sh
for((i=10000;i<=12000;i++))
do
        for((k=2;k<=i;k++))
        do
                if [ $k -eq $i ]
                then
                        echo "$i su shu"
                        break

                fi
                if [ $(($i%k)) -eq 0 ]
                then break
                fi
        done
done

 

 

 

#!/bin/bash

i=19000
N=20000

while [ "$i" -lt "$N" ]
do
        flag=1
        j=2
        k=$(echo "sqrt($i)"|bc)
        while [ "$j" -le "$k" ]
        do
                let "m = $i % $j"
                if [ "$m" -eq 0 ]
                then
                        flag=0
                fi
                let "j = $j + 1"
        done
        if [ "$flag" -eq 1 ]
        then
                echo $i
        fi
        let "i = $i + 1"
done