How to copy path of a file in Mac OS?
All you need to do to copy any items path name directly to the clipboard from anywhere in the file system:

Navigate to the file or folder you wish to copy the path for Right-click (or Control+Click, or a Two-Finger click on trackpads) on the file or folder in the Mac Finder
While in the right-click menu, hold down the OPTION key to reveal the “Copy (item name) as Pathname” option, it replaces the standard Copy option Once selected, the file or folders path is now in the clipboard, ready to be pasted anywhere

The copied pathname is always the complete path, it’s not relative.
You can get the same result with a keyboard shortcut of Command+Option+C.
Source http://osxdaily.com/2015/11/05/copy-file-path-name-text-mac-os-x-finder/