Add a help target to a Makefile that will allow all targets to be self documenting

Makefile

# Add the following 'help' target to your Makefile
# And add help text after each target name starting with '\#\#'
 
help:           ## Show this help.
	@fgrep -h "##" $(MAKEFILE_LIST) | fgrep -v fgrep | sed -e 's/\\$$//' | sed -e 's/##//'
 
# Everything below is an example
 
target00:       ## This message will show up when typing 'make help'
	@echo does nothing
 
target01:       ## This message will also show up when typing 'make help'
	@echo does something
 
# Remember that targets can have multiple entries (if your target specifications are very long, etc.)
target02:       ## This message will show up too!!!
target02: target00 target01
	@echo does even more

just to add another variant to the pile..

• uses only sed for pre-processing the makefile
• uses tput to detect if we should use colour
• uses column for what it does best

help:
	@sed \
		-e '/^[a-zA-Z0-9_\-]*:.*##/!d' \
		-e 's/:.*##\s*/:/' \
		-e 's/^\(.\+\):\(.*\)/$(shell tput setaf 6)\1$(shell tput sgr0):\2/' \
		$(MAKEFILE_LIST) | column -c2 -t -s :

What's the most cross-platform solution, without colors and which displays targets even if they don't have comment?

@arvenil i might be wrong but i think that a makefile works using the same system, across all platforms? Please correct me if i am wrong, i am not very cross platform myself... As for color, i guess the terminal will be responsible for displaying it (or not) depending on the context. Many tools have the ability to force the suppression of color, too.

@arvenil Depends on what you want to depend on? You have choices. awk, sed, grep, bash, sh, zsh, GNU Make, BSD Make, Linux, MacOS, BSD, WSL, RHEL/Fedora, Debian, Ubuntu, others. For widest cross compatibility, GNU Make and bash are fairly safe. But bash has been losing install base and mind share with MacOS and other smaller Linux distros changing their default shells.

One other note, since GNU Make is the most popular, it has a fairly powerful and underutilized optional integration of GNU Guile. GNU Guile is language in the Scheme & Lisp family of languages.

If Guile is a bridge too far, then consider bash's BASH_REMATCH facility.

It'll be a bit more code (file I/O, regexes, file parsing, etc) and you'll have to maintain it rather than depending on other well tested tooling like awk, sed, grep.

@arvenil A bit of golfing and I got this to sort of work with the only deps being GNU make and bash

SHELL:=/bin/bash
.PHONY: help help_target-funky+names.0k and_with_2_targets_and_spaces_like_bison
help_target-funky+names.0k and_with_2_targets_and_spaces_like_bison: ## Funky ones & bison dual target display ok
        echo "bad - why are you not displaying?"
help: ## bash help
help: ## moar bash help
        @RE='^[a-zA-Z0-9 ._+-]*:[a-zA-Z0-9 ._+-]*##' ; while read line ; do [[ "$$line" =~ $$RE ]] && echo "$$line" ; done <$(MAKEFILE_LIST) ; RE=''

Which for make help outputs

$ make help
help_target-funky+names.0k and_with_2_targets_and_spaces_like_bison: ## Funky ones & bison dual target display ok
help: ## bash help
help: ## moar bash help

I thought I'd throw my hat into the ring:

## Usage: make <target>
##   This makefile generates a WhatzIt report, suitable for pasting into Slack.
##   It prints the report to the screen, and also puts it in the copy-paste buffer
##
## Possible Targets:

usage: ## Displays this message
        @gawk -vG=$$(tput setaf 2) -vR=$$(tput sgr0) ' \
          match($$0,"^(([^:]*[^ :]) *:)?([^#]*)##(.*)",a) { \
            if (a[2]!="") {printf "%s%-36s%s %s\n",G,a[2],R,a[4];next}\
            if (a[3]=="") {print a[4];next}\
            printf "\n%-36s %s\n","",a[4]\
          }\
        ' $(MAKEFILE_LIST)

example.txt : example.json ## Make the Example

Lines starting with ## are printed as-is (the text after the ##).
Lines starting with a target and ending with ## get the target printed in green, and the text after the ## printed starting in column 37.
A further refinement would be to send the output through column -t -s@ or similar, to align the columns efficiently.

Since it's the first target in the Makefile, it runs if make is run with no arguments. I hate playing "guess the usage message flag". 🎏 😃

I'll look into Guile, didn't know about it, and I thought I'd read the make docs enough times to have stumbled over it. 😃

Here's an iteration on @PenelopeFudd's version with a few small improvements:

• It can be added to the end of the Makefile because .DEFAULT_GOAL is used
• It ignores commented targets
• It ignores certain kinds of headers that can be useful to organize targets not mentioned in the help text

##
## These lines show up in the final output,
##including leading whitespace.
##
## They are useful for end-user documentation.
##

# Note that sections like the following are ignored in the help output; they are
# meant for developer documentation.

##
## generate target files
##

################################################################################
# File copies - easy stuff
################################################################################

target3.txt: target2.txt ## Generate target3.txt
	cp $< $@

target2.txt: target1.txt ## Generate target2.txt
	cp $< $@

################################################################################
# This one could be complicated or require further explanation to a developer.
################################################################################

target1.txt: # (this one is undocumented)
	touch $@

##
## other stuff
##

file4.txt: ## Generate file4.txt
	touch $@

##
## tools and help
##

lint: ## run linter

################################################################################
# Help target
################################################################################
help:: ## show this help text
	@gawk -vG=$$(tput setaf 2) -vR=$$(tput sgr0) ' \
	  match($$0, "^(([^#:]*[^ :]) *:)?([^#]*)##([^#].+|)$$",a) { \
	    if (a[2] != "") { printf "    make %s%-18s%s %s\n", G, a[2], R, a[4]; next }\
	    if (a[3] == "") { print a[4]; next }\
	    printf "\n%-36s %s\n","",a[4]\
	  }' $(MAKEFILE_LIST)
	@echo -e "" # blank line at the end
.DEFAULT_GOAL := help

##@
##@ Clean build files commands
##@

kernel-%-clean: ##@ Clean kernel build files with specified architecture
                ##@ e.g. kernel-amd64-clean / kernel-arm64-clean
	$(MAKE) -C ./arch/kernel/$* clean

rootfs-%-clean: ##@ Clean rootfs build files with specified architecture
                ##@ e.g. rootfs-amd64-clean / rootfs-arm64-clean
	$(MAKE) -C ./arch/rootfs/$* clean

clean: ##@ Clean all build files
	$(MAKE) kernel-amd64-clean
	$(MAKE) kernel-arm64-clean
	$(MAKE) rootfs-amd64-clean
	$(MAKE) rootfs-arm64-clean

##@
##@ Misc commands
##@

help: ##@ (Default) Print listing of key targets with their descriptions
	@printf "\nUsage: make <command>\n"
	@grep -F -h "##@" $(MAKEFILE_LIST) | grep -F -v grep -F | sed -e 's/\\$$//' | awk 'BEGIN {FS = ":*[[:space:]]*##@[[:space:]]*"}; \
	{ \
		if($$2 == "") \
			pass; \
		else if($$0 ~ /^#/) \
			printf "\n%s\n", $$2; \
		else if($$1 == "") \
			printf "     %-20s%s\n", "", $$2; \
		else \
			printf "\n    \033[34m%-20s\033[0m %s\n", $$1, $$2; \
	}'

I tried @BlackHole1 's solution and got this :(

Usage: make <command>
awk: illegal statement
 input record number 1, file 
 source line number 1```

I tried @BlackHole1 's solution and got this :(

Usage: make <command>
awk: illegal statement
 input record number 1, file 
 source line number 1```

@Windowsfreak Can you share the contents of your makefile? It works fine on my local machine.

@Windowsfreak I just reproduced this issue on macOS. you need to install gawk first (brew install gawk).

AWK := awk
ifeq ($(shell uname -s), Darwin)
	AWK = gawk
    ifeq (, $(shell which gawk 2> /dev/null))
        $(error "gawk not found")
    endif
endif

-	@grep -F -h "##@" $(MAKEFILE_LIST) | grep -F -v grep -F | sed -e 's/\\$$//' | awk 'BEGIN {FS = ":*[[:space:]]*##@[[:space:]]*"}; \
+ 	@grep -F -h "##@" $(MAKEFILE_LIST) | grep -F -v grep -F | sed -e 's/\\$$//' | $(AWK) 'BEGIN {FS = ":*[[:space:]]*##@[[:space:]]*"}; \

Full Code:

AWK := awk
ifeq ($(shell uname -s), Darwin)
	AWK = gawk
    ifeq (, $(shell which gawk 2> /dev/null))
        $(error "gawk not found")
    endif
endif

##@
##@ Clean build files commands
##@

kernel-%-clean: ##@ Clean kernel build files with specified architecture
                ##@ e.g. kernel-amd64-clean / kernel-arm64-clean
	$(MAKE) -C ./arch/kernel/$* clean

rootfs-%-clean: ##@ Clean rootfs build files with specified architecture
                ##@ e.g. rootfs-amd64-clean / rootfs-arm64-clean
	$(MAKE) -C ./arch/rootfs/$* clean

clean: ##@ Clean all build files
	$(MAKE) kernel-amd64-clean
	$(MAKE) kernel-arm64-clean
	$(MAKE) rootfs-amd64-clean
	$(MAKE) rootfs-arm64-clean

##@
##@ Misc commands
##@

help: ##@ (Default) Print listing of key targets with their descriptions
	@printf "\nUsage: make <command>\n"
	@grep -F -h "##@" $(MAKEFILE_LIST) | grep -F -v grep -F | sed -e 's/\\$$//' | $(AWK) 'BEGIN {FS = ":*[[:space:]]*##@[[:space:]]*"}; \
	{ \
		if($$2 == "") \
			pass; \
		else if($$0 ~ /^#/) \
			printf "\n%s\n", $$2; \
		else if($$1 == "") \
			printf "     %-20s%s\n", "", $$2; \
		else \
			printf "\n    \033[34m%-20s\033[0m %s\n", $$1, $$2; \
	}'

@Windowsfreak @BlackHole1 no need for gawk, just replace pass with empty printf and problem solved. BSD awk does not know pass command.

		if($$2 == "") \
-			pass; \
+			printf ""; \

$ PATH="/usr/bin:/usr/sbin:/bin:/sbin" make help

Usage: make <command>

Clean build files commands

    kernel-%-clean       Clean kernel build files with specified architecture
                         e.g. kernel-amd64-clean / kernel-arm64-clean

    rootfs-%-clean       Clean rootfs build files with specified architecture
                         e.g. rootfs-amd64-clean / rootfs-arm64-clean

    clean                Clean all build files

Misc commands

    help                 (Default) Print listing of key targets with their descriptions

Many good suggestions.
I felt the help syntax a bit ugly when having several target dependancies.
99% of my targets are non-files, and therefor PHONY targets. So I put the check on the PHONY targets only.

This doesn't fit everyone, but maybe gives some one some thougths.

PHONY: help ## Show this help.
help:
	@grep -he '^PHONY:.*##' $(MAKEFILE_LIST) | sed -e 's/ *##/:\t/' | sed -e 's/^PHONY: *//'

I think writing a "makefile-helper <makefile_list>" in perl will be my next approach. I got many Makefiles, and copy/paste any advanced script into each Makefile is just bad.

@kjellericson you could use include /absolute/or/relative/path/to/*.mk instead of embedding it into each Makefile directly.

Hi, just discovered this gist/conversation from a google search. The solution by @BlackHole1 (Oct 26, 2023) meets my needs 90%.
But in some of our makefiles we have a dependency after the target, like this:

app: $(APP_FILE2).exe $(APP_FILE2).exe ##@ Build the applications

The items after the ":" are displayed in the help, and I really don't want this.

I am not conversant enough in awk/gawk to figure out how to suppress the display of the items after the ":"
Can anyone give me advice?

Thanks!

Hi @chrissv, you can repeat the target twice. Once for the help comment and the other one for the list of dependencies. With your example:

app: ##@ Build the applications
app: $(APP_FILE2).exe $(APP_FILE2).exe

Hi @chrissv, you can repeat the target twice. Once for the help comment and the other one for the list of dependencies. With your example:

app: ##@ Build the applications
app: $(APP_FILE2).exe $(APP_FILE2).exe

That's a great suggestion, thanks!

I find it difficult to maintain awk one liners across various makefiles. This is a version organised in a script.