echo “Hello World”is equal to
/usr/bin/echo “Hello World”
"man is the system's manual pager. Each page argument given to man is normally the name of a program, utility or function. The manual page associated with each of these arguments is then found and displayed. A section, if provided, will direct man to look only in that section of the manual. The default action is to search in all of the avail‐ able sections following a pre-defined order (see DEFAULTS), and to show only the first page found, even if page exists in several sections."
-lhrefers to list, human readable. Type
man lsto see more arguments.
-r(recursive) flag needs to be used.