       rehash [ -df ]
              Throw out the command hash table  and  start  over.
              If  the  -f  option is set, rescan the command path
              immediately, instead of rebuilding the  hash  table
              incrementally.

              The  -d  option  causes  rehash to act on the named
              directory table instead of the command hash  table.
              This  reduces the named directory table to only the
              `~' entry.  If the -f  option  is  also  used,  the
              named directory table is rebuilt immediately.

              rehash is equivalent to hash -r.
