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golang在编译时用ldflags设置变量的值

2019-11-18 · 3 min read
golang

命中注定:编译阶段注入变量值

The Go linker (go tool link) has an option to set the value of an uninitialised string variable:

-X importpath.name=value
  Set the value of the string variable in importpath named name to

value. Note that before Go 1.5 this option took two separate arguments. Now it takes one argument split on the first = sign.

As part of your build process, you could set a version string variable using this. You can pass this through the go tool using -ldflags. For example, given the following source file:

package main

import "fmt"

var xyz string

func main() {
    fmt.Println(xyz)
}

Then:

$ go run -ldflags "-X main.xyz=abc" main.go
abc

In order to set main.minversion to the build date and time when building:

go build -ldflags "-X main.minversion=`date -u +.%Y%m%d.%H%M%S`" service.go

If you compile without initializing main.minversion in this way, it will contain the empty string.

通过git tag 设置代码版本

# This how we want to name the binary output
BINARY=gomake

# These are the values we want to pass for VERSION and BUILD
# git tag 1.0.1
# git commit -am "One more change after the tags"
VERSION=`git describe --tags`
BUILD=`date +%FT%T%z`

# Setup the -ldflags option for go build here, interpolate the variable values
LDFLAGS=-ldflags "-w -s -X main.Version=${VERSION} -X main.Build=${BUILD}"

# Builds the project
build:
    go build ${LDFLAGS} -o ${BINARY}

# Installs our project: copies binaries
install:
    go install ${LDFLAGS}

# Cleans our project: deletes binaries
clean:
    if [ -f ${BINARY} ] ; then rm ${BINARY} ; fi

.PHONY: clean install

该 make file 将会构建一个 version 是git tag 的可执行文件

示例代码如下:

package main

import (
    "fmt"
)

var (
    Version string
    Build   string
)

func main() {
    fmt.Println("Version: ", Version)
    fmt.Println("Build Time: ", Build)
}

执行:

# make
# ./gomake
Version:  1.0.1-1-gfb51187
Build Time:  2016-09-07T22:41:38+0200