best way to replace first word in string?

[Chris F.A. Johnson]

On 2005-10-22, William Park wrote:
> hagai26 at gmail.com <hagai26 at gmail.com> wrote:
>> I am looking for the best and efficient way to replace the first word
>> in a str, like this:
>> "aa to become" -> "/aa/ to become"
>> I know I can use spilt and than join them
>> but I can also use regular expressions
>> and I sure there is a lot ways, but I need realy efficient one
>
> I doubt you'll find faster than Sed.

   On the contrary; to change a string, almost anything will be faster
   than sed (except another external program).

   If you are in a POSIX shell, parameter expansion will be a lot
   faster.

   In a python program, one of the solutions already posted will be
   much faster.

-- 
    Chris F.A. Johnson                     <http://cfaj.freeshell.org>
    ==================================================================
    Shell Scripting Recipes: A Problem-Solution Approach, 2005, Apress
    <http://www.torfree.net/~chris/books/cfaj/ssr.html>