\documentclass{article} % We use the article class ... 
\usepackage{splitidx} % ... and the splitidx package 

\makeindex % And we want index generation 

% We define 4 indices: 
\newindex[General Index] 
{idx} % Name and shortcut of the 1st index 
\newindex[Index of Animals] 
{ani} % ... 2nd index 
\newindex[Index of Fruits] 
{fru} % ... 3rd index 
\newindex[Index of Vegetables] 
{veg} % ... 4th index 

\listfiles

\begin{document} 

Apples\sindex[fru] 
{apple} % an entry to fru index 
and oranges\sindex[fru] 
{orange} % an entry to fru index 
are fruits\sindex 
{fruits}. % an implicit entry to idx index 
Tomatoes\sindex[veg] 
{tomato} % an entry to veg index 
are 
vegetables\index 
{vegetables}. % an implicit entry to idx index 
Cats\sindex[ani] 
{cat} % an entry to ani index 
are animals\sindex[idx] 
{animals}. % an explicite entry to idx index 

\printindex* % print all indices 

\end {document}