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KarlsD
KarlsD

Reputation: 667

Makefile: shell command execution

I have the following simple statement that works without problems in the shell:

if [ -z "$(command -v brew)" ]; then
 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
fi

in short: if the program is not found, then install it.

The problem is that I can't convert this construction into a Makefile. So far I understand that the construction itself should look like this:

if [ -z "$(shell command -v brew)" ]; then \
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" \
fi

But how to correctly convert /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" string I do not quite understand. Could you give some tips in this matter?

Upvotes: 1

Views: 3074

Answers (2)

John Kugelman
John Kugelman

Reputation: 361556

The dollar signs need to be doubled so make doesn't interpret them. Also there needs to be a semicolon at the end of the bash command to separate it from fi since the backslash will eat the usual newline command separator.

some_target:
        if [ -z "$$(command -v brew)" ]; then \
          /bin/bash -c "$$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"; \
        fi

Upvotes: 3

Anya Shenanigans
Anya Shenanigans

Reputation: 94584

You need to break it into a couple of items.

Firstly, check for brew:

BREW := $(shell command -v brew)

Then check if the variable is set. If it's not set, then run the installer:

ifeq ($(BREW),)
    $(shell bash -c "$$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)")
    BREW := $(shell command -v brew)
endif

It's doable in an entire single shell command, but this breaks it into a couple of shell pieces.

the use of := means that the evaluation happens at the time the line is parsed, which is how you get to check and override the value.

In a small, self-contained makefile:

BREW := $(shell command -v brew)

ifeq ($(BREW),)
$(shell bash -c "$$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)")
BREW := $(shell command -v brew)
endif

all:
    echo $(BREW)

Upvotes: 1

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