ifeq

Makefile

.PHONY: all

b:
        $(eval N := $(shell echo "100"))

p: b
ifeq ($(CMD),a)
        $(eval B := $(shell expr $N + 10 ))
else
        $(eval B := $(shell expr $N + 20 ))
endif

all: p
        @echo $(B)
        
        
# $ make all CMD=a
# 110
# $ make all CMD=b
# 120