Two or three things about environment variables of golang

There are many environment variables in golang. After we install go, we usually focus on GOPATH and GOROOT, as well as several environment variables related to go mod. We don't know much about other variables. If we want to know more about this language, we need to know other environment variables.

Let's take a general look at the following environmental variables and what they mean:

$ go help environment
The go command and the tools it invokes consult environment variables
for configuration. If an environment variable is unset, the go command
uses a sensible default setting. To see the effective setting of the
variable <NAME>, run 'go env <NAME>'. To change the default setting,
run 'go env -w <NAME>=<VALUE>'. Defaults changed using 'go env -w'
are recorded in a Go environment configuration file stored in the
per-user configuration directory, as reported by os.UserConfigDir.
The location of the configuration file can be changed by setting
the environment variable GOENV, and 'go env GOENV' prints the
effective location, but 'go env -w' cannot change the default location.
See 'go help env' for details.

General-purpose environment variables:

        GCCGO
                The gccgo command to run for 'go build -compiler=gccgo'.
        GOARCH
                The architecture, or processor, for which to compile code.
                Examples are amd64, 386, arm, ppc64.
        GOBIN
                The directory where 'go install' will install a command.
        GOCACHE
                The directory where the go command will store cached
                information for reuse in future builds.
        GODEBUG
                Enable various debugging facilities. See 'go doc runtime'
                for details.
        GOENV
                The location of the Go environment configuration file.
                Cannot be set using 'go env -w'.
        GOFLAGS
                A space-separated list of -flag=value settings to apply
                to go commands by default, when the given flag is known by
                the current command. Each entry must be a standalone flag.
                Because the entries are space-separated, flag values must
                not contain spaces. Flags listed on the command line
                are applied after this list and therefore override it.
        GOOS
                The operating system for which to compile code.
                Examples are linux, darwin, windows, netbsd.
        GOPATH
                For more details see: 'go help gopath'.
        GOPROXY
                URL of Go module proxy. See 'go help modules'.
        GOPRIVATE, GONOPROXY, GONOSUMDB
                Comma-separated list of glob patterns (in the syntax of Go's path.Match)
                of module path prefixes that should always be fetched directly
                or that should not be compared against the checksum database.
                See 'go help module-private'.
        GOROOT
                The root of the go tree.
        GOSUMDB
                The name of checksum database to use and optionally its public key and
                URL. See 'go help module-auth'.
        GOTMPDIR
                The directory where the go command will write
                temporary source files, packages, and binaries.

Environment variables for use with cgo:

        AR
                The command to use to manipulate library archives when
                building with the gccgo compiler.
                The default is 'ar'.
        CC
                The command to use to compile C code.
        CGO_ENABLED
                Whether the cgo command is supported. Either 0 or 1.
        CGO_CFLAGS
                Flags that cgo will pass to the compiler when compiling
                C code.
        CGO_CFLAGS_ALLOW
                A regular expression specifying additional flags to allow
                to appear in #cgo CFLAGS source code directives.
                Does not apply to the CGO_CFLAGS environment variable.
        CGO_CFLAGS_DISALLOW
                A regular expression specifying flags that must be disallowed
                from appearing in #cgo CFLAGS source code directives.
                Does not apply to the CGO_CFLAGS environment variable.
        CGO_CPPFLAGS, CGO_CPPFLAGS_ALLOW, CGO_CPPFLAGS_DISALLOW
                Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
                but for the C preprocessor.
        CGO_CXXFLAGS, CGO_CXXFLAGS_ALLOW, CGO_CXXFLAGS_DISALLOW
                Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
                but for the C++ compiler.
        CGO_FFLAGS, CGO_FFLAGS_ALLOW, CGO_FFLAGS_DISALLOW
                Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
                but for the Fortran compiler.
        CGO_LDFLAGS, CGO_LDFLAGS_ALLOW, CGO_LDFLAGS_DISALLOW
                Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
                but for the linker.
        CXX
                The command to use to compile C++ code.
        FC
                The command to use to compile Fortran code.
        PKG_CONFIG
                Path to pkg-config tool.

Architecture-specific environment variables:

        GOARM
                For GOARCH=arm, the ARM architecture for which to compile.
                Valid values are 5, 6, 7.
        GO386
                For GOARCH=386, the floating point instruction set.
                Valid values are 387, sse2.
        GOMIPS
                For GOARCH=mips{,le}, whether to use floating point instructions.
                Valid values are hardfloat (default), softfloat.
        GOMIPS64
                For GOARCH=mips64{,le}, whether to use floating point instructions.
                Valid values are hardfloat (default), softfloat.
        GOWASM
                For GOARCH=wasm, comma-separated list of experimental WebAssembly features to use.
                Valid values are satconv, signext.

Special-purpose environment variables:

        GCCGOTOOLDIR
                If set, where to find gccgo tools, such as cgo.
                The default is based on how gccgo was configured.
        GOROOT_FINAL
                The root of the installed Go tree, when it is
                installed in a location other than where it is built.
                File names in stack traces are rewritten from GOROOT to
                GOROOT_FINAL.
        GO_EXTLINK_ENABLED
                Whether the linker should use external linking mode
                when using -linkmode=auto with code that uses cgo.
                Set to 0 to disable external linking mode, 1 to enable it.
        GIT_ALLOW_PROTOCOL
                Defined by Git. A colon-separated list of schemes that are allowed
                to be used with git fetch/clone. If set, any scheme not explicitly
                mentioned will be considered insecure by 'go get'.
                Because the variable is defined by Git, the default value cannot
                be set using 'go env -w'.

Additional information available from 'go env' but not read from the environment:

        GOEXE
                The executable file name suffix (".exe" on Windows, "" on other systems).
        GOGCCFLAGS
                A space-separated list of arguments supplied to the CC command.
        GOHOSTARCH
                The architecture (GOARCH) of the Go toolchain binaries.
        GOHOSTOS
                The operating system (GOOS) of the Go toolchain binaries.
        GOMOD
                The absolute path to the go.mod of the main module,
                or the empty string if not using modules.
        GOTOOLDIR
                The directory where the go tools (compile, cover, doc, etc...) are installed.

You can view your go environment variables using the following command:

$ go env

In addition to some environment variables related to go mod, we won't talk about some environment variables related to GOPATH, because I talked about go mod in the last article. Next, we'll learn about other environment variables.

GOARCH and GOOS

GOARCH: cpu architecture, 386, amd64, arm, etc. are set during cross compilation, and packages of different platforms can be compiled.
GOOS: platform, linux, windows, etc., usually used in combination with Google.
Here are the commands for cross compilation on different platforms:

Mac Compile below Linux, Windows 64 bit executable of the platform:
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build test.go
CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build test.go

Linux Compile below Mac, Windows 64 bit executable of the platform:
CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 go build test.go
CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build test.go

Windows Compile below Mac, Linux 64 bit executable of the platform:
SET CGO_ENABLED=0
SET GOOS=darwin
SET GOARCH=amd64
go build test.go
SET CGO_ENABLED=0
SET GOOS=linux
SET GOARCH=amd64
go build test.go

GOCACHE

This is the cache generated by go build, which can speed up compilation. I see a README file in the path printed by GOCACHE, which explains GOCACHE.

This directory holds cached build artifacts from the Go build system.
Run "go clean -cache" if the directory is getting too large.
See golang.org to learn more about Go.

You can use the "go clean -cache" command to clear the compilation cache.

GOENV

The local go environment file storage location cannot be set with "go env -w".

Summary

The above is the first stage of understanding environment variables of golang, and there are some environment variables to be continued in the next article.

Welcome to my public address. onepunchgo Will sort out related documents and materials.

Tags: Go Windows Linux git Mac

Posted on Thu, 16 Jan 2020 01:38:38 -0500 by mark_18