Shell__循环

num=1
while [ $num -le 3 ]
do
    echo ${num}
    num=$(($num+1))
done

shell的循环也有多种写法：
http://bbs.linuxpk.com/thread-39584-1-1.html

time for i in `seq 1000000`; 
    do echo $i> /dev/null; 
done
real        0m35.109s
user        0m29.126s
sys        0m5.436s

time for i in {1..1000000}; 
    do echo $i> /dev/null; 
done
real        0m32.997s
user        0m27.350s
sys        0m5.184s

time for ((i=0;i<1000000;i++)); 
    do echo $i> /dev/null; 
done
real        0m38.951s
user        0m32.370s
sys        0m5.836s

遍历当前目录

#!/bin/sh
for file in ./* 
do
    if test -f $file
    then
        echo $file
        echo 是文件
    fi
    if test -d $file
    then
        echo $file
        echo 是目录
    fi
done