Using visdiff

The /Applications/VisualDiffer.app/Contents/Helpers folder contains the executable file visdiff that integrates with VisualDiffer.app
You can launch visdiff to visually show files or folders comparison using the following syntax

visdiff <left file or folder> <right file or folder>

Note: On versions older than 1.8.0 visdiff is located at /Applications/VisualDiffer.app/Contents/Resources/visdiff

Wait for document close

If you need to wait the user closes the diff document window (not necessary to quit application) associated to visdiff command you can pass the switch --wait

For example

$ visdiff ~/original.txt ~/modified.txt --wait

Creating a symbolic link

VisualDiffer.app doesn’t install the terminal application but manually it is possible to create the link to the shell command.
It requires root access, from a terminal prompt type the command shown below

$ sudo ln -s /Applications/VisualDiffer.app/Contents/Helpers/visdiff /usr/bin/visdiff

Note: VisualDiffer can’t install command line tool from its User Interface to comply with Apple’s submission guidelines

OSX sandbox, temporary files and annoying file open panel prompts

VisualDiffer was sandboxed starting from version 1.4.2 and many users found using it very annoying because any comparison prompts to pick folders/files.
This problem was fixed on version 1.4.3 introducing the so called “Trusted Paths”, please refer to Trusted Paths for further details