How Can I Escape Dollar Sign Interpolation in Makefile Commands?

Escaping Expression Interpolation in a Makefile Command

Issue:

Encountering difficulties interpolating an expression within a command in a Makefile due to evaluation issues.

Explanation:

A Makefile uses different evaluation rules compared to a shell script. In a Makefile, the dollar sign ($) is used for variable expansion, but when used within a command, it may not be evaluated as intended.

Solution:

To escape the $ in a Makefile command and enable shell-like expression interpolation, use a second dollar sign ($$). This tells the Makefile to treat the first $ as literal text and defer interpolation to the shell.

Example:

To run tests in a Go project, but skip vendor tests, you can use the following Makefile snippet:

test:
    go test $$(go list ./... | grep -v /vendor/)

.PHONY: test

In this example, the $$(go list ./... | grep -v /vendor/) is enclosed within double dollars to ensure that the expression is interpolated by the shell.

By escaping the dollar sign, the Makefile correctly evaluates the expression and provides the expected output.

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