问在运行shell脚本时，我如何动态地更改主机？

EN

#!/bin/bash
# Setting Environment Platform
init(){
    echo "Enter username of guest machine"
    read USERNAME    
    echo "Enter IP of guest machine"
    read GUEST_IP
    echo "Guest IP : $GUEST_IP"   
    echo "Guest Username $USERNAME"
    echo "running === ssh -l $USERNAME $GUEST_IP"
    if ssh -l $USERNAME $GUEST_IP; then
        install_packages
        echo SUCCESS
    else 
        retry_connection
        echo FAIL
    fi
}
# Scripts for package installation on remote host.
install_packages(){
    sudo apt-get -y update && apt-get -y upgrade
    sudo apt-get -y install aptitude
    sudo apt-get -y install default-jre
    sudo apt-get -y install default-jdk
}
retry_connection(){
    if ssh -l $USERNAME $GUEST_IP; then
        install_packages
        echo SUCCESS
    else 
        retry_connection
        echo FAIL
    fi
}