Makefile hacks: print the value of any variable
The print-% rule is a slick hack, but it’s a nuisance to have to modify a makefile just to use it. Worse, you might not even be able to modify the makefile. Fortunately, there’s a solution: the -f command-line option. You’re probably familiar with it — that’s how you tell gmake to use a different makefile than the default Makefile when it starts. For example, if you have a makefile named build.mak :
What you may not know is that you can use multiple -f options on the command line. GNU make will read each file in turn, incorporating the contents of each just as if they were included with the include directive. We can create a simple makefile called printvar.mak containing nothing but our print-% rule, then inject it into any makefile we want like this:
The combination of the print-% rule and the -f command-line option is powerful, but it’s unwieldy — too many characters to type. The solution is a shell script wrapper:
