How do I make multiple targets from a set of templates for the source?

Question

I have targets identified by a version number (7.0 7.1 7.2)

I have some templates that have a placeholder that needs to be replaced for each version such that I end up with a directory for each version with all the files in each directory having the appropriate replacements.

So, if the template directory is :

template\Dockerfile

I want to end up with :

7.0\Dockerfile
7.1\Dockerfile
7.2\Dockerfile

with the the tag in the template\Dockerfile being replaced with the version number.

This is a simplified example. There are actually 4 files in the template folder (and 2 are in a subdirectory).

A pipeline will run make build-targets and then the appropriate docker commands to build the containers and push them to the repository - that's the goal.

Whilst it would be nice to have an answer to all of this, I would like to learn, but I can't find anything about how to deal with sets of sources and sets of targets.

Any advice would be appreciated.

More details in response to comments

The versions are currently just 1 line in the Makefile: VERSIONS := 7.0 7.1 7.2 latest

The code to run will be a series of sed commands to take a template and replace a #version# tag in the file with the version number (except for latest in which case it will just remove the tag.

The template sources are all in the templates directory. As part of the sed command, the resulting filename will have the part templates replaced with the version (including latest).

A start ... (no idea if this is good or not - still learning)

VERSIONS  := 7.0 7.1 7.2 latest
SOURCEDIR := ./templates
DESTDIR   := ./
TEMPLATES := $(shell find $(SOURCEDIR) -type f)

# For each file in $(TEMPLATES) for each version in $(VERSIONS), create a corresponding file in $(DEST_DIR)/$(VERSION)
# Replace `#version#` with $(VERSION) in each file, except for the `latest` target where the `#version#` removed.

Based upon solutions provide below, my final code is:

VERSIONS := 7.0 7.1 7.2 latest
SOURCE_DIR := ./templates
TEMPLATES := $(shell find $(SOURCE_DIR) -type f)
TEMPLATES := $(patsubst $(SOURCE_DIR)/%,%,$(TEMPLATES))
DEST_DIR := ./

.DEFAULT_GOAL := all
.PHONY: all

# $(1): version
# $(2): template file (without the $(SOURCE_DIR)/ stem)
define generate_target_file
$(DEST_DIR)/$(1)/$(2): $(SOURCE_DIR)/$(2)
    @echo "Making $$@"
    @mkdir -p $$(dir $$@)
    @if [ "$(1)" == "latest" ]; then \
        sed 's/#version#//g' $$< > $$@; \
    else \
        sed 's/#version#/$(1)-/g' $$< > $$@; \
    fi

all: $(DEST_DIR)/$(1)/$(2)
endef

$(foreach version,$(VERSIONS),$(foreach template,$(TEMPLATES),$(eval $(call generate_target_file,$(version),$(template)))))

list:
    @echo 'The following targets are available :'
    @$(MAKE) -pRrq -f $(lastword $(MAKEFILE_LIST)) : 2>/dev/null | \
        awk -v RS= -F: '/^# File/,/^# Finished Make data base/ {if ($$1 !~ "^[#.]") {print $$1}}' | \
        sort | \
        egrep -v -e '^[^[:alnum:]]' -e '^$@$$' | \
        xargs -0

As usual with make, things are much easier if you already know how to do what you want to automate on the Command Line Interface (CLI). Can you show: 1) where the list of version numbers come from? 2) what you would do on the CLI for a version number? — Renaud Pacalet, Oct 12 '18 at 05:51
I've added some more comments to the question. The bit I can't work out is how to (or if I should) define all the targets (every `$(TEMPLATE)` for every `$(VERSION)`). — Richard A Quadling, Oct 12 '18 at 10:42
Your question is now much clearer. See my answer for a GNU-make starting point. — Renaud Pacalet, Oct 12 '18 at 12:21

Renaud Pacalet · Accepted Answer · 2018-10-12T12:22:38.277

If you are using GNU-make, you can easily create loops with make's foreach function. And you can nest them. The eval function can be used to programmatically instantiate make constructs and the call function allows you to create kind of macros:

V := 7.0 7.1 7.2 latest
S := ./templates
T := $(shell find $(S) -type f)
T := $(patsubst $(S)/%,%,$(T))
D := ./destdir

.DEFAULT_GOAL := all
.PHONY: all

# $(1): version
# $(2): template file (without the $(S)/ stem)
# $(3): replacement string
define MY_rule
$(D)/$(1)/$(2): $(S)/$(2)
    mkdir -p $$(dir $$@)
    sed 's/#version#/$(3)/g' $$< > $$@

all: $(D)/$(1)/$(2)
endef

$(foreach v,$(V),\
  $(foreach t,$(T),\
    $(eval $(call MY_rule,$(v),$(t),$(patsubst latest,,$(v))))))

The GNU make manual explains how this works. Beware the double expansion of the MY_rule macro, reason why some $ signs must be doubled.

I didn't quite understand the `$$< > $$@` bit initially, but https://stackoverflow.com/questions/3220277/what-do-the-makefile-symbols-and-mean helped there. Thank you. — Richard A Quadling, Oct 12 '18 at 16:30

How do I make multiple targets from a set of templates for the source?

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