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bashmakefile

What does "$$?" mean in this makefile snippet?

What does "$$?" mean in below Makefile snippet?

$(PROGS): FORCE
    @cd $(BUILD_DIRECTORY_PATH)/$@; \
    mkdir -p obj; \
    $(MAKE) || exit "$$?"; \  <====== HERE

ADD 1

I guess it means exit "$?" in bash since $$ in makefile escapes to $.

But what does exit "$?" mean then?

Solution

  • $? is the return code when a program exits or finishes. Therefore, in your line

    $(MAKE) || exit "$$?"

    It will execute $(MAKE). If this program does not finish correctly, it will have a return code different from 0 and then the exit "$$?" will be executed. which will make the current process to exit to shell with the same return code as the $(MAKE) program, which you will be able to show executing echo $? in the shell.