Auto-install packages from inside makefile

Question

Goal: when the user types 'make packages', automatically search for the package libx11-dev (required for my program to compile) and, if not found, install it. Here's a stripped-down version of my makefile:

PACKAGES = $(shell if [ -z $(dpkg -l | grep libx11-dev) ]; then sudo apt-get install libx11-dev; fi)

[other definitions and targets]

packages: $(PACKAGES)

When I type 'make packages', I'm prompted for the super-user password. If entered correctly, it then hangs indefinitely.

Is what I'm trying to do even possible from within the makefile? If so, how?

Thanks so much.

Answer 1

The problem is that the shell function acts like backticks in the shell: it takes the output to stdout and returns it as the value of the function. So, apt-get is not hanging, it's waiting for you to enter a response to some question. But you cannot see the question because make has taken the output.

The way you're doing this is not going to work. Why are you using shell instead of just writing it as a rule?

packages:
        [ -z `dpkg -l | grep libx11-dev` ] && sudo apt-get install libx11-dev
.PHONY: packages

Answer 2

I figured out a better way, which avoids the problem of having unexpected arguments to the if statement:

if ! dpkg -l | grep libx11-dev -c >>/dev/null; then sudo apt-get install libx11-dev; fi

The -c flag on grep makes it return the number of lines in dpkg -l which contain the string libx11-dev, which will either be 0 (if uninstalled) or 1 (if installed), allowing

dpkg -l | grep libx11-dev -c  

to be treated like an ordinary boolean variable.