How to open directly the help/reference window from a notebook

Question

I'm used to do

??symbol

when I want the reference for a given symbol, then I click on the >> arrows to open the help window.

Would it be possible to redefine the meaning of ?? in order to open the reference window directly ?

Answer 1

The simplest (and canonical) method is to place the keyboard cursor in the Symbol name, or select it with a double-click, and press F1 if you use Windows/Linux or Command-Shift-F if you use OS X. This will bring up the Help for that item. This also works with compound operators, e.g. /;.

Nevertheless I like a challenge, therefore:

$PreRead =
  # /. RowBox[{"??", name_String}] :>
    FrontEndTokenExecute["OpenHelpLink", name] &;

Now this brings up the Help page for Fold directly:

?? Fold

While this will search the documentation for the term "Fold":

?? "Fold"

I chose $PreRead for this purpose so that it will not interfere with internal calls to Information.
You can also get the original behavior by writing out Information, e.g.:

? Plus

x+y+z represents a sum of terms.  >>

Information[Plus]  (* equivalent to ??Plus *)

x+y+z represents a sum of terms.  >>

Attributes[Plus]={Flat,Listable,NumericFunction,OneIdentity,Orderless,Protected}

Default[Plus]:=0

Answer 2

The typical way to search the documentation is the keyboard shortcut Mr Wizard mentioned. In general, you can find the shortcut key for a command by looking in the menu ...

If you are looking for a built-in way to open a documentation pages using a built-in command, then you are looking for Documentation`HelpLookup.

Documentation`HelpLookup["euler"]

will open the documentation centre and do a search for "euler". It returns a reference to the notebook window containing the search result. The behaviour equivalent to typing the search term into the documentation search box.