+ \begin{itemize}
+ \item Make builds things on the basis of timestamps
+ \item But what if the contents haven't changed and it's expensive to
+ rebuild?
+ \item Use md5sum!
+ \end{itemize}
+\begin{minted}[showtabs,breaklines]{make}
+TARGET: PREREQ1 PREREQ1
+ if [ -e $@.target.md5sum ] && [ -e $@ ] && \
+ md5sum --status --check $@.target.md5sum; \
+ then \
+ touch $@; \
+ else \
+ RECIPE FOR $@; \
+ md5sum $^ > $@.target.md5sum; \
+ fi;
+\end{minted}