When golang is compiled, ldflags is used to assign values ​​to variables in the package to print version numbers and commits.

Many command line programs can output version information, commit, operating system and other information through the version parameter. The following introduces a method to print the version number of the command line program compiled by golang.

The version information printed by docker:

$ ~ docker version
Client: Docker Engine - Community
Version: 18.09.2
API version: 1.39
Go version: go1.10.8
Git commit: 6247962
Built: Sun Feb 10 04:12:39 2019
OS/Arch: darwin/amd64
Experimental: false
Server: Docker Engine - Community
Engine:
Version: 18.09.2
API version: 1.39 (minimum version 1.12)
Go version: go1.10.6
Git commit: 6247962
Built: Sun Feb 10 04:13:06 2019
OS/Arch: linux/amd64
Experimental: false

The implementation is to use a parameter of go build -ldflags. Enter go help build and you can see a configuration item:

-ldflags 'flag list' arguments to pass on each go tool link invocation.


This parameter is used to set some parameters of go link (static link). The specific parameters can be viewed through go tool link --help.

The -X parameter can be assigned to variables in the package during compilation. Then we use the flag package to set the version parameter to print the version number. .

main.go：

package main
import (
"flag"
"log"
"os "
)
var (
Version string
Branch string
Commit string
BuildTime string
lowercase string // Lowercase is also acceptable
)
func main( ) {
versionFlag := flag.Bool("version", false, "print the version")
flag.Parse()
if *versionFlag {
log.Printf("Version: % s\n", Version)
log.Printf("Branch: %s\n", Branch)
log.Printf("Commit: %s\n", Commit)
log.Printf( "BuildTime: %s\n", BuildTime)
log.Printf("lowercase: %s\n", lowercase)
os.Exit(0)
}
log.Println(" run main.go")
}

Packaging script:

#!/usr/bin/env bash
prog=xxx
version=1.1.0
lowercase=ok
# Cross-compile
# CGO_ENABLED=0 GOOS=linux GOARCH=amd64
go build -ldflags "\
- X main.Version=$version \
-X main.Branch=`git rev-parse --abbrev-ref HEAD` \
-X main.Commit=`git rev-parse HEAD` \
-X main.BuildTime=`date -u ' %Y-%m-%d_%H:%M:%S'` \
-X main.lowercase=$lowercase \
" -v -o $prog main.go

Final effect:

$ ./xxx -version
2019/04/11 00: 59:08 Version: 1.1.0
2019/04/11 00:59:08 Branch: master
2019/04/11 00:59:08 Commit: 29921d9df18543693321e2109ea36462dbb346d3
2019/04/11 00: 59:08 BuildTime: 2019-04-10_16:59:07
2019/04/11 00:59:08 lowercase: ok