Bourne shell version. As the shell finds commands along the search path ($PATH), it remembers the found location in an internal hash table. The next time you enter a command, the shell uses the value stored in its hash table.
With no arguments, hash
lists the current hashed commands. The display shows hits
(the number of times the command is called by the shell) and cost
(the level of work needed to find the command). Commands that were found in a relative directory have an asterisk (
With commands , the shell will add those commands to the hash table.