How to print out a variable in makefile

Question

In my makefile, I have a variable \'NDK_PROJECT_PATH\', my question is how can I print it out when it compiles?

I read Make file echo displaying "$PATH" st

Answer 1

Run make -n; it shows you the value of the variable..

Makefile...

all:
        @echo $(NDK_PROJECT_PATH)

Command:

export NDK_PROJECT_PATH=/opt/ndk/project
make -n 

Output:

echo /opt/ndk/project

Answer 2

from a "Mr. Make post" https://www.cmcrossroads.com/article/printing-value-makefile-variable

Add the following rule to your Makefile:

print-%  : ; @echo $* = $($*)

Then, if you want to find out the value of a makefile variable, just:

make print-VARIABLE

and it will return:

VARIABLE = the_value_of_the_variable

Answer 3

No need to modify the Makefile.

$ cat printvars.mak
print-%:
        @echo '$*=$($*)'

$ cd /to/Makefile/dir
$ make -f ~/printvars.mak -f Makefile print-VARIABLE

Answer 4

@echo $(NDK_PROJECT_PATH) is the good way to do it. I don't think the error comes from there. Generally this error appears when you mistyped the intendation : I think you have spaces where you should have a tab.

Answer 5

This can be done in a generic way and can be very useful when debugging a complex makefile. Following the same technique as described in another answer, you can insert the following into any makefile:

# if the first command line argument is "print"
ifeq ($(firstword $(MAKECMDGOALS)),print)

  # take the rest of the arguments as variable names
  VAR_NAMES := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS))

  # turn them into do-nothing targets
  $(eval $(VAR_NAMES):;@:))

  # then print them
  .PHONY: print
  print:
          @$(foreach var,$(VAR_NAMES),\
            echo '$(var) = $($(var))';)
endif

Then you can just do "make print" to dump the value of any variable:

$ make print CXXFLAGS
CXXFLAGS = -g -Wall

Answer 6

I usually echo with an error if I wanted to see the variable value.(Only if you wanted to see the value. It will stop execution.)

@echo $(error NDK_PROJECT_PATH= $(NDK_PROJECT_PATH))