rehash updates the MATLAB^® list of known files and classes for folders on the search path that are not in matlabroot. It compares the timestamps for loaded functions against their timestamps on disk. It clears loaded functions if the files on disk are newer. All of this normally happens each time MATLAB displays the Command Window prompt. Use rehash with no arguments only when you run a program file that updates another program file, and the calling file needs to use the updated version of the second file before the calling file has finished running.

rehash path performs the same updates as rehash, except that it unconditionally updates the list of known files and classes for all folders on the search path that are not in matlabroot. Run rehash path only if you receive a warning during MATLAB startup notifying you that MATLAB could not tell if a folder has changed, and you encounter problems with MATLAB not using the most current versions of your program files.

rehash toolbox performs the same updates as rehash path, except it updates the list of known files and classes for all folders on the search path, including those in matlabroot. Run rehash toolbox when you change, add, or remove files in matlabroot during a session. Typically, you should not make changes to files and folders in matlabroot.

rehash toolboxcache performs the same updates as rehash toolbox, and also updates the cache file. This is equivalent to clicking the Update Toolbox Path Cache button in the General Preferences dialog box.