====== Makefiles ======
Makefiles are command files used by the "make" or "gmake" system to create a software system (or sometimes other object, such as documentation) from sources. 

The important thing for //users// to remember is\\
== Never Execute a Makefile ==
The syntax is fairly different from shell or other scripts; nevertheless, it occurs surprisingly often that a shell interpreter is able to 'interpret' the first few lines of a makefile. If, as often occurs, the first template happens to be one for uninstalling the package, the results can be disastrous. For example, if the variables $dir, $base and $ext haven't been initialised in a way the shell can understand, then
  rm $dir/$base*$ext
might well get interpreted as 
  rm /*

======  ======

The important thing for //developers// to remember is\\
== Always protect Users from Executing a Makefile ==
For the reasons above, I strongly recommend, if you are writing a makefile, to include as early as possible in your file something like:

  # Template to protect users against accidentally 
  # executing a makefile - skipped if called by make
  # if called as a script,
  # it should barf on the unexpected "ifeq", 
  # but even if it manages to ignore that, 
  # it should print and exit
  # Note that this protection is needed, because makefiles 
  # can sometimes be valid shell scripts - witness the  
  # standard XMILL makefile that manages to skip errors
  # till it gets to
  # clean:
  #	rm -r -f $(TMP)/* $(TARGETS)
  # when executed in most unix shells - 
  # which isn't very nice if $(TMP) is undefined...
  ifeq (1,0)
    echo "THIS IS NOT A SHELL SCRIPT!!!!"
    echo "IT IS A CONFIGURATION FILE FOR THE make SYSTEM"
    echo "DO NOT EXECUTE IT"
    exit 1
  endif

This won't affect the execution of the makefile at all, because 1 will never equal 0 (so the nested part will never even be seen by make)

It works as a protection in all unix shells I have tried; it may not work as well in DOS, but I assume it would at least cause an abort.