Go build LDFlags

README.md

Using the -ldflags parameter can help set variable values at compile time.

Using the example provided here:

1. Running make build will create a build executable. Running it will result in:

$> ./build
no version (Mon YYYY)
$>

2. Running make build_version will use the version and date variables defined in the makefile and using the -ldflags option to set the values of version and date in main.go.

$> ./build
0.0.1 (Aug 2017)
$>

useful links

• https://blog.cloudflare.com/setting-go-variables-at-compile-time/

main.go

package main

var (
	version string
	date    string
)

func init() {
	if version == "" {
		version = "no version"
	}
	if date == "" {
		date = "(Mon YYYY)"
	}
}

func main() {
	println(version, date)
}

makefile

version=0.0.1
date=$(shell date -j "+(%b %Y)")
exec=a.out

.PHONY: all

all:
	@echo " make <cmd>"
	@echo ""
	@echo "commands:"
	@echo " build          - runs go build"
	@echo " build_version  - runs go build with ldflags version=${version} & date=${date}"
	@echo ""

build: clean
	@go build -v -o ${exec}

build_version: check_version
	@go build -v -ldflags '-X "main.version=${version}" -X "main.date=${date}"' -o ${exec}_${version}

clean:
	@rm -f ${exec}

check_version:
	@if [ -a "${exec}_${version}" ]; then \
		echo "${exec}_${version} already exists"; \
		exit 1; \
	fi;