什麼是錯的，在這個簡單的Makefile

Question

SRC_VAR = test string for variable manipulation. 

TEST1_VAR = $(subset for,foo,${SRC_VAR}) 

all: 
    @echo original str: ${SRC_VAR} 
    @echo substitution: ${TEST1_VAR} 

這是輸出：

original str: test string for variable manipulation. 

substitution: 

輸出應該是：

original str: My test string for variable manipulation. 

substitution: My test string foo variable manipulation. 

Answer 1

取代命令subst，不subset。