shell的循环

语法
for 变量名 in 取值列表    {#取值列表可以是数字 字符串 序列 命令} 以空格分隔
do
       命令的集合
done

for 手 in 苹果 梨 香蕉 橘子  变量的值 依次从左到右读取
do
    echo 包裹${手}
done

#!/bin/sh
for i in {1..254}
do
     {
     IP=10.0.0.$i
     ping -c1 -W1 $IP &>/dev/null
     if [ $? -eq 0 ];then
     echo "ping $IP is ok"
     fi } &
done
wait
echo "在线取IP完成"

#!/bin/sh
for i in `cat user.txt`
do
   id $i &>/dev/null
   if [ $? -eq 0 ];then
         echo "useradd:$i already exists"
   else
          useradd $i &>/dev/null
          if [ $? -eq 0 ];then
                echo "create $i is ok"
          else
                echo "error"
          fi
         pass=`echo $((RANDOM))|md5sum|cut -c1-8`
         echo $pass|passwd --stdin $i &>/dev/null
         [ $? -eq 0 ] && echo "密码创建成功" || echo "密码创建失败"
         echo -e "$i\t$pass" >> pass.txt
    fi
done

#!/bin/bash
sum=0
for ((i=1;i<101;i++))
do
    ((sum+=i))
done
echo $sum

#!/bin/sh
>ran.txt
touch ran.txt
while true
do
RAN=`echo $((RANDOM%100+1))`
    if [ `grep -w $RAN ran.txt|wc -l` -eq 1 ];then
       continue
    fi
read -p "请输入你的姓名: " name
if [ $name = "exit" ];then
     echo "抓阄完毕统计结果如下"
     sort -rnk2 ran.txt 
     exit
else
    if [ `grep -w $name ran.txt|wc -l` -eq 1 ];then
    echo "抓过阄了不要闹了"
    continue
    else
    echo -e "$name\t$RAN"|tee -a ran.txt
    fi
fi
done

while [ 条件测试 ]
do
  命令的集合
done


#!/bin/sh
while [ 10 -gt 10 ]
do
    sleep 1
    echo ok
done

#!/bin/sh
while read user
do
    useradd $user &>/dev/null
    if [ $? -eq 0 ];then
    echo "ok"
    else
    echo "error"
    fi
done<user.txt

<user.txt 从文件中读取用户名 在循环里执行

exit
[root@shell ~]# cat exit.sh
#!/bin/sh
while true
do
     echo hehe
     exit
     echo test
done
echo done......

break
[root@shell ~]# cat break.sh 
#!/bin/sh
while true
do
     echo hehe
     break
     echo test
done
echo done......

continue
[root@shell ~]# cat break.sh
#!/bin/sh
while true
do
     echo hehe
     continue
     echo test
done
echo done......