Using MKS Make

How Make Finds Files
If you specify the .SOURCE or .SOURCE.x targets more than once,
MKS Make appends all the prerequisites to one list. However, you can clear
the list of prerequisites by specifying the target with a null prerequisite list.
In addition, you can use MKS Make’s :- rule operator to clear a previously
set list of path names. Thus, the following two examples are equivalent.
.SOURCE :
.SOURCE : /usr/fred /usr/gerry
# these two lines are equivalent to the next one
.SOURCE :- /usr/fred /usr/gerry
More generally, the processing of the .SOURCE special targets is identical to
the processing of the .SUFFIXES special targets.
Example: Directory Navigation Within a Makefile
Sometimes you might want to have a recipe run while the directory is set to
something else other than the current directory. The .SETDIR attribute tells
make to change the current directory for the duration of the recipe with the
attribute set. Here’s an example:
all: subdir two
echo not in subdir
pwd
# Remember to clean up afterwards by
# removing subdir.
subdir:
mkdir subdir
# Note: We can't put "subdir" as a prerequisite
# for "two" because subdir has to exist before
# anything to do with "two" is processed.
two .SETDIR=subdir:
echo in subdir
pwd
Note that .SETDIR does not work with metarules.
Example: Including External Makefiles
Make has facilities for including other makefiles into the current makefile.
Normally, make looks in the current directory for these files. The special
targets, .INCLUDEDIRS and .INCLUDE, can be used to inform make to look
elsewhere for these files.
The following example relates back to the following three makefiles, two of
which are located in the subdirectories 1 and 2.
Using MKS Make 41