请问这是什么意思

Question

我正在编写 .sh 脚本用于在服务器上上传应用程序并更正 echo 下载失败 $...

c=country  like cz,us,sk etc
change of my echo fail to download $ on : echo cant find ${c^^}

Please, what means ${c^^} and ${c,,} 

谢谢