Question

I’m having hard time writing a makefile rule that outputs a multiline variable in a file.

Here is the code I have :

define VAR1
    /dev d 755 - - - - -
endef

define VAR2
    /test d 777 - - - - -
    /test2 d 777 - - - - -
endef

VARS += $(VAR1)
VARS += $(VAR2)

all:
    echo "$(VARS)" > test

However, the echo fails telling “Unterminated quoted string” for a reason unknown to me.
How could i put in the file every lines declared on a separate line ?

Answer 1

If you export the variable to the shell and reference it as a shell variable, rather than a make variable, you will have better luck:

define VAR1
    /dev d 755 - - - - -
endef

define VAR2
    /test d 777 - - - - -
    /test2 d 777 - - - - -
endef

define VARS
$(VAR1)
$(VAR2)
endef
export VARS

all:
    echo "$$VARS" > test

Note the following adjustments to your makefile:

• I used define to create VARS, rather than a series of += assignments, which makes it easier to get a newline between the value of VAR1 and VAR2.
• I added export VARS to your makefile, to get the variable pushed into the environment for the shell invocation.
• I used $$VARS rather than $(VARS) to dereference it — that leaves the expansion to the shell, rather than to make, which will avoid the “Unterminated quoted string” error.