Makefile Functions & Text Processing

OUT := $(subst src/,build/,$(SRC))

# Replace every occurrence of one string with another.

OBJ := $(patsubst %.c,%.o,$(SRC))

# Replace words matching a `%` pattern.

NAME := $(strip $(NAME))

# Trim extra leading, trailing, and repeated internal whitespace.

HAS_TEST := $(findstring test,$(MAKECMDGOALS))

# Return the search string if found.

FIRST := $(word 1,$(FILES))
REST := $(wordlist 2,$(words $(FILES)),$(FILES))

# Extract words by position.

CURRENT_MK := $(lastword $(MAKEFILE_LIST))

# Grab the first or last word of a list.

PAIRS := $(join a b c,.o .d .map)

# Concatenate corresponding words from two lists.

BINS := $(addprefix dist/,$(TARGETS))
OBJ := $(addsuffix .o,$(NAMES))

# Add text to every word in a list.

DIRS := $(dir $(FILES))
BASE := $(basename $(FILES))

# Split and recombine filenames.

ROOT := $(realpath .)
CACHE := $(abspath .cache)

# Normalize paths.

MODE_MSG := $(if $(CI),ci-mode,local-mode)

# Select one of two expansions based on non-empty condition text.

PORT := $(or $(APP_PORT),3000)

# Return the first non-empty argument.

READY := $(and $(DB_URL),$(API_KEY),yes)

# Return the last argument if all are non-empty.

RESULT := $(intcmp $(JOBS),8,lt,eq,gt)

# Compare integers in GNU make 4.4+.

GIT_SHA := $(shell git rev-parse --short HEAD)

# Capture shell command output at parse time.

define banner
$(info === $(1) ===)
endef

$(call banner,Deploying API)

# Invoke a user-defined macro like a function.

define make-test-target
.PHONY: test-$(1)
test-$(1):
  pytest -q tests/$(1)
endef

$(foreach p,unit integration e2e,$(eval $(call make-test-target,$(p))))

# Generate new rules dynamically.

RAW_RULE := $(value SOME_TEMPLATE)

# Read a variable without expanding it.

$(file >build/version.txt,$(VERSION))

# Write content to a file from make.

$(warning building with DEBUG=$(DEBUG))
$(if $(DB_URL),,$(error DB_URL is required))

# Emit diagnostics or abort parsing.

$(info Sources: $(SRC))

# Print information during parsing.

.PHONY: help
help:
  @grep -E '^[a-zA-Z0-9_.-]+:.*?## ' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "%-24s %s
", $$1, $$2}'

# Extract target comments from the current makefile.

$(info goals=$(MAKECMDGOALS))

# Inspect requested goals.

CURRENT_MK := $(lastword $(MAKEFILE_LIST))

# Get the most recently parsed makefile path.

empty :=
space := $(empty) $(empty)
comma := ,

# Create reusable space or comma variables.