CODEWITHSUNDEEP
linuxmacrosmakefilecommand
bob.sacamento
bob.sacamento

Reputation: 6651

Make: How to store result of a command in a macro?

I have a makefile that doesn't do much yet:

SRCS = *FOR

OBJS = $(SRCS:.FOR=.o)

tell_srcs: $(SRCS)
    echo $(SRCS)

tell_objs:  $(OBJS)
    echo $(OBJS)

make tell_srcs operates as I hoped, returning

file1.FOR file2.FOR file3.FOR ....

However, make tell_objs returns the exact same thing:

file1.FOR file2.FOR file3.FOR ....

which is not what I expected nor need.

I guess the point is that make is not really storing the results of *FOR in $(SRCS), but is storing the actual *FOR "command" in $(SRCS), and the substitution I tried to do to get $(OBJS) has no effect ... I guess. Anyway, is there a way to get make to store the actual output of *FOR in $(SRCS) so it will function as a regular macro? Thanks.

BTW, here's version info:

 >make -v
 GNU Make 3.81

Upvotes: 1

Views: 93

Answers (1)

ash
ash

Reputation: 5155

Try this:

SRCS = $(shell echo *FOR)

OBJS = $(SRCS:.FOR=.o)

tell_srcs: $(SRCS)
    echo $(SRCS)

tell_objs:  $(OBJS)
    echo $(OBJS)

The SRCS = *.FOR sets SRCS to *.FOR, not the shell-expanded result of *.FOR. So, when OBJS is processed it tries to change .FOR at the end of *FOR. I suspect you tried *.FOR in SRCS and ran into the problem that the use of OBJS gave *.o or the list of all .o files in the directory.

make -p can help in these cases, although I suspect this case would still have been a mystery.

Upvotes: 2

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