for添加用户

#!/bin/bash

#接受一个参数：
#add: 添加用户user1..user10
#del: 删除用户user1..user10
#其它：退出

#定义变量
ADD=add
DEL=del

#判断参数输入是否正确
if [ $# -ne 1 ]; then
  echo "Usage:./shell.sh add|del."
  exit 1

#输入add，添加用户
elif [ $1 = $ADD ]; then
  for I in {1..10}; do
    if ! id "user$I" &> /dev/null; then
      useradd -M "user$I"
      echo "add user$I OK."
    else
      echo "user$I exist.There's no need to newadd."
    fi
  done

#输入del，删除用户
elif [ $1 = $DEL ]; then
  for I in {1..10}; do
    if id "user$I" &> /dev/null; then
      userdel -r "user$I"
      echo "del user sucessfully."
    else
      echo "user$I not exist,no need to delete."
    fi
  done
else
  echo "tip:./shell.sh add|del."
fi