shell脚本变量

ACTION()
{
read -p "please input username: " USERNAME
[ "$USERNAME" = "exit" ] && {
        echo exit
        exit
}
id "$USERNAME" &> /dev/null && {
        echo "$USERNAME" is exist
        ACTION
}||{
        echo $USERNAME is not exist
        read -p "please input password: " PASSWORD
        useradd $USERNAME
        echo $PASSWORD | passwd --stdin $USERNAME
        echo $USERNAME is created
        ACTION
}
 
}
ACTION

实现的功能是添加和删除用户。用户可以选择添加或删除，如果选择删除，会要求输入用户名，然后进行删除；如果选择添加，则先检查用户是否已经存在，如果存在则提示用户已经存在，如果不存在，则要求输入密码，然后创建用户并设置密码。

echo "[d]elete [A]dd"
read -p "please input action:" ACTION
[ "$ACTION"  != "a" -a "$ACTION" != "d" ]  && {
        echo wrong action
        exit
}
 
[ "$ACTION" = "d" ] && {
        read -p "please input username:" USERNAME
        id $USERNAME &> /dev/null && {
        userdel -r $USERNAME
        echo $USERNAME is deleted
}||{
        echo $USERNAME is not exist
}
        exit
}
 
[ "$ACTION" = "a" ] && {
        read -p "please input username:" USERNAME
        id $USERNAME &> /dev/null && {
        echo $USERNAME is exist
}||{
        read -p "please input password: " PASSWORD
        useradd $USERNAME
        echo $PASSWORD | passwd --stdin $USERNAME
        echo $USERNAME is created
}
        exit
}