Dollar in conditional variable assignment operator in Makefile-CodePudding

Is it possible to pass value with single dollar from shell to Makefile, or I it is only way to put double dollar in bash and then to call make?

Makefile is:

HASH ?= $$6$$salt$$val

.PHONY: tst
tst:
        echo '$(HASH)'

Command to run:

> make HASH='$6$salt$val'
echo 'altal'
altal

If I use double quotes, all is fine:

> make HASH='$$6$$salt$$val'
echo '$6$salt$val'
$6$salt$val

But is it possible do not make substitution $ to $$ in bash?

CodePudding user response：

Try this:

In console:

export HASH='$6$salt$val'; make

in Makefile:

.PHONY: tst
tst:
        @echo "$$HASH"

Result:

$6$salt$val

CodePudding user response：

How about writing the initialisation within the file identical to the one coming from the command line? The below script demonstrates how to rewrite a variable with the override directive:

quote-one-level = $(eval override $1=$(subst $,$$$$,$(value $1)))

var-info = $(info $1=$(value $1) flavour=$(flavor $1) origin=$(origin $1))

A ?= $abc

$(call var-info,A)
$(call quote-one-level,A)
$(call var-info,A)

$(call var-info,B)
$(call quote-one-level,B)
$(call var-info,B)

export A
export B

all:
    @echo A = '$(A)'
    @echo B = '$(B)'
ifeq ($(MAKELEVEL),0)
    $(MAKE)
endif

Inflating one $ to $$$$ (and not just $$) is necessary because the eval command literally generates make code, thereby obviously reducing the quoting level by one. Resulting output:

$ make B='$abc'
A=$abc flavour=recursive origin=file
A=$$abc flavour=recursive origin=override
B=$abc flavour=recursive origin=command line
B=$$abc flavour=recursive origin=override
A = $abc
B = $abc
make
make[1]: Entering directory 
A=$abc flavour=recursive origin=environment
A=$$abc flavour=recursive origin=override
B=$abc flavour=recursive origin=command line
B=$$abc flavour=recursive origin=override
A = $abc
B = $abc
make[1]: Leaving directory