帮我用Linux shell 写一个用户管理系统

好的，以下是一个简单的用户管理系统的Linux shell脚本：

#!/bin/bash

while true
do
    clear
    echo "User Management System"
    echo "1. Add User"
    echo "2. Delete User"
    echo "3. Modify User"
    echo "4. View User List"
    echo "5. Exit"
    echo -n "Please enter your choice: "
    read choice

    case $choice in
        1) # add user
            echo -n "Please enter the username: "
            read username
            echo -n "Please enter the password: "
            read password
            sudo useradd -m -s /bin/bash $username
            echo "$username:$password" | sudo chpasswd
            echo "User $username has been added successfully."
            read -p "Press [Enter] key to continue..."
            ;;
        2) # delete user
            echo -n "Please enter the username to delete: "
            read username
            sudo userdel -r $username
            echo "User $username has been deleted successfully."
            read -p "Press [Enter] key to continue..."
            ;;
        3) # modify user
            echo -n "Please enter the username to modify: "
            read username
            echo -n "Please enter the new password: "
            read password
            echo "$username:$password" | sudo chpasswd
            echo "User $username has been modified successfully."
            read -p "Press [Enter] key to continue..."
            ;;
        4) # view user list
            sudo cat /etc/passwd | awk -F: '{ print $1 }'
            read -p "Press [Enter] key to continue..."
            ;;
        5) # exit
            exit 0
            ;;
        *) # invalid option
            echo "Invalid option. Please try again."
            read -p "Press [Enter] key to continue..."
            ;;
    esac
done

这个脚本提供了以下功能：

1. 添加用户
2. 删除用户
3. 修改用户密码
4. 查看用户列表
5. 退出程序

使用该脚本需要使用管理员权限，因此需要使用 `sudo` 命令执行操作。