If you have emptied the Trash folder of Mac, then there is very less probability of data recovery using the OS X itself. Terminal will be of no help to recover deleted files using command lines. However, still you can recover your deleted files.
First Method: Restore data from Time Machine Backup
If you have previously setup Time Machine backup, then all your files and folder are stored on the Time Machine. In addition, data restoration from Time Machine is quite and you can take the help from this article to restore your deleted data back.
Second Method: Use a Mac data recovery program:
Data recovery software can help you to recover deleted Trash data back within minutes. They uses advanced file recovery algorithms and provide immediate recovery to data-loss. I personally recommend you to download and install Stellar Phoenix Mac Data Recovery utility for deleted file recovery. The software is also capable of recovering deleted files from Time Machine, BootCamp and Password Protected Hard Drives.
Always keep an external hard drive reserved for serving you for Time Machine backups. Other backup options for your Mac files are BlackBaze software to do full backup of Mac disk. Always rely on two-backup strategy.