Shell循环语句

for 变量名 in [ 取值列表 ]
do
    循环体
done

#!/bin/bash
for i in $(cat user.txt)
do
    id $i &>/dev/null
    if [ $? -eq 0 ];then
        echo "user $username is already exists"
    else
        useradd $i &&         echo "123.com" |passwd --stdin $i &>/dev/null
        echo "$i Is OK"
    fi
done

## 当条件测试成立（条件测试为真），执行循环体
while 条件测试
do
    循环体
done

#!/bin/bash
while read user
do
    username=$(echo $user|awk ‘{print $1}‘)
    password=$(echo $user|awk ‘{print $2}‘)
    id $username &>/dev/null
    if [ $? -eq 0 ];then
        echo "user $username is already exists"
    else
        useradd $username 
        if [ $? -eq 0 ];then
        echo "$password"|passwd --stdin $username &>/dev/null
        echo "useradd $username is Created Passwd Is Ok."
        fi
    fi
done<user.txt