Custom parameters

Summary

You can pass variables to your Makefile using environment variables or using key-value pairs. Or a mix of both.

Values below available in Makefile. Note case sensitivity - pass as bar=1 if you want to use as bar.

$ BAR=1 make foo

$ export BAR=1 
$ make foo

$ make foo BAR=abc

Use a variable

Here is the sample file we’ll use for testing in the section sections

• Makefile

    foo:
        @echo $(FOO)            # Make variable.
        @echo $${FOO}           # Shell variable.
        @bash -c 'echo "$$FOO"' # Subshell.
  

Note that FOO will be available for commands, without having to export it like this:

• Makefile

    export FOO
  
    foo:
        # ...
  

Pass a variable

Use any approach below to get the same result.

Export environment variable

$ export FOO=bar
$ make foo

bar
bar
bar

Pass as environment variable

$ FOO=bar make foo

bar
bar
bar

Pass as keyword parameter

$ make foo FOO=bar
$ # OR
$ make FOO=bar foo

bar
bar
bar

Validate

Check that a variable is set.

Add an if statement with a help message and exit command.

SITE_URL = $(url)

check:
	@if [[ -z "$(SITE_URL)" ]]; then \
		echo "'url' must be set"; \
		exit 1; \
	fi
	@echo "URL: $(SITE_URL)"

Usage:

$ make check          
'url' must be set
make: *** [check] Error 1
$ make check url='https://example.com'   
URL: https://example.com

Python

e.g. Here using Python Docker container as a drop-in placement for the python command.

python:
	if [[ "$(SCRIPT_PATH)" == '' ]]; then echo 'required param: SCRIPT_PATH'; exit 1; fi

	docker run -it --rm \
		--name my-python-app \
		-v "$(PWD):/usr/src/myapp" \
		-w /usr/src/myapp \
		python:3.9 \
		python $(SCRIPT_PATH)
        
greet:
    $(MAKE) python SCRIPT_PATH='hello.py'

Run as:

$ make python SCRIPT_PATH='hello.py

Or with a hardcoded value:

$ make greet

Rename variable

See also the Definition page setting a default value for an input variable.

Perhaps you want to pass a variable name with a short name or different case on the shell, then use it under another name in the Makefile.

Here we rename a variable from v to VERSION using shell evaluation.

• Makefile

    VERSION := $(v)
  
    show-vsn:
        @echo "Target version: $(VERSION)"
  

In the shell:

$ export v=1.2.3
$ make show-version
Target version: 1.2.3

Rename variable and set a default

If you want to pass your value as an argument to make as lowercase but convert it to uppercase and also give a default value.

• Makefile

    version ?= 13
    VERSION = $(version)
  
    show-vsn:
        @echo "Target version: $(VERSION)"
  

In the shell:

$ make show-version version=1.2.3
Target version: 1.2.3

Note on syntax

Note you have to do keyword options.

Any arguments for make as targets to run.

This will as BAR=1 as a variable in Makefile.

$ make foo BAR=1

This will run make foo and make BAZZ and fail:

$ make foo BAR