Update Workflow management

Workflow-management.md

@@ -32,17 +32,6 @@ acyclic graph*. This allows two things:
 These two features together provide a solid step towards reproducible simulation
 work.
 
-# GNU Make
-Make is a program specifically designed to be a build system, i.e. a tool that
-coordinates the compilation of a program's source code so that an executable or
-library can be built. Each file of the build process is called a *target* and is
-the output of some rule. Although it's primary purpose is creating build files,
-it can easily be made to manage outputs of simulations. While it has the
-advantage of being installed on virtually every Linux machine used for
-scientific work, it lacks some features (most notably integration with queue
-systems) which only make it practical for small cases (although I am sure some
-shortcomings could be solved with a strong knowledge of Make).
-
 # Snakemake
 Snakemake is a tool written in Python to managed rule-based workflows. The
 workflow definition is a rather simple text file (usually a `Snakefile`), which
@@ -171,3 +160,30 @@ Here is a list of useful features:
   the name.
 - [Parameter space
   exploration](https://snakemake.readthedocs.io/en/stable/snakefiles/rules.html#parameter-space-exploration).
+
+# GNU Make
+Make is a program specifically designed to be a build system, i.e. a tool that
+coordinates the compilation of a program's source code so that an executable or
+library can be built. Each file of the build process is called a *target* and is
+the output of some rule. Although it's primary purpose is creating build files,
+it can easily be made to manage outputs of simulations. While it has the
+advantage of being installed on virtually every Linux machine used for
+scientific work, it lacks some features (most notably integration with queue
+systems) which only make it practical for small cases (although I am sure some
+shortcomings could be solved with a strong knowledge of Make).
+
+For reference, here is a `Makefile` defining the same rules as the Snakemake example above.
+
+```makefile
+# One input, one output
+groups_with_users.txt: /etc/group
+        cat $< | awk -F ':' '$$4 != "" { print $$1,$$4; }' > $@
+
+# Multiple outputs with grouped targets
+sorted_groups.txt only_users.txt &: groups_with_users.txt
+        sort < $< | tee sorted_groups.txt | cut -d ' ' -f 2 > only_users.txt
+
+# Rule with pattern
+start_with_letter_%.txt: groups_with_users.txt
+        grep '^$*' < $< > $@
+```