All paths to directories with Linux commands are stored within a variable called $PATH. Once a command is being called its path is stored additionally in a notebook called hash to speed up the look up next time. 

The hash is a shell builtin command and `help hash` gives a very short description. One option -t is described as printing all paths collected within the hash, and so I typed:

 hash -t

being sure I would get a listing of the hash's content.

However I got this:

> bash: hash: -t: option requires an argument

 

 - What argument does it require?

 

 - What am I doing wrong?

 

 - How to show the content of the hash table?