How do I get `make` to prompt the user for a password and store it in a Makefile variable?

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I'm writing a Makefile, and some of the commands the makefile runs require a password. I'd like to give the user the ability to either pass this in as a Makefile variable using make PASSWORD=password or if the user does not pass it in, then prompt the user for it and store their response in said Makefile variable.

At the moment, I'm able to check the Makefile variable, and then as part of my target specific rules, write shell commands that prompt the user for the password and store it in a shell variable. However, this variable is only available to that specific shell and not any others.

How do I read something from the user and store it in a variable?

I've tried the following:

PASSWORD ?= $(shell read -s -p "Password: " pwd; echo $pwd)

but the prompt is never printed. I've also tried echo "Password: " inside shell, but that isn't printed either.

Any ideas?

Edit:

To clarify, the password needs to be set for a specific target, so I have something like this:

PASSWORD := 

my-target: PASSWORD ?= $(shell read -s -p "Password: " pwd; echo $$pwd)

my-target:
    # rules for mytarget that use $(PASSWORD)

Edit 2:

I found the problem. When I set PASSWORD := at the top of the script, it sets PASSWORD to an empty string, and this in turn causes the ?= to be skipped (since PASSWORD) is already set.

makefile bash
2 Answers

To answer @joeb 's question:

$ make; echo "---Makefile---"; cat Makefile
Password: <hidden>
test
test
---Makefile---
all: first second
PASSWORD ?= $(shell read -s -p "Password: " pass; echo $$pass)
define formatted
first:
        @echo $1
second:
        @echo $1
endef

$(eval $(call formatted,$(PASSWORD)))
user_19792300
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