Can I list all standard Go packages?

Question

Is there a way in Go to list all the standard/built-in packages (i.e., the packages which come installed with a Go installation)?

I have a list of packages and I want to figure out which packages are standard.

Supernumerary

Default Go packages golang.org/pkg – Toshikotoss

Is there a function like isStandardPackage(importPath string) bool which i can use? – Supernumerary

can this be used? golang.org/pkg/cmd/go/internal/list ? – Supernumerary

I think list to show you all install packages. – Toshikotoss

what are you trying to achieve here? An import statement without a . is either an internal package of your own or a part of the standard library. – Stokehole

We were trying to organize code in kubernetes. We need a easy way to figure out in one of the scripts if this a standard package and can be ignored for analysis. – Supernumerary

Answer 1

You can use the new golang.org/x/tools/go/packages for this. This provides a programmatic interface for most of go list:

package main

import (
    "fmt"

    "golang.org/x/tools/go/packages"
)

func main() {
    pkgs, err := packages.Load(nil, "std")
    if err != nil {
        panic(err)
    }

    fmt.Println(pkgs)
    // Output: [archive/tar archive/zip bufio bytes compress/bzip2 ... ]
}

To get a isStandardPackage() you can store it in a map, like so:

package main

import (
    "fmt"

    "golang.org/x/tools/go/packages"
)

var standardPackages = make(map[string]struct{})

func init() {
    pkgs, err := packages.Load(nil, "std")
    if err != nil {
        panic(err)
    }

    for _, p := range pkgs {
        standardPackages[p.PkgPath] = struct{}{}
    }
}

func isStandardPackage(pkg string) bool {
    _, ok := standardPackages[pkg]
    return ok
}

func main() {
    fmt.Println(isStandardPackage("fmt"))  // true
    fmt.Println(isStandardPackage("nope")) // false
}

Olmos

Immediately searched where does ok come from and found this nice article. reddit.com/r/golang/comments/35d0b2/about_the_comma_ok_idiom – Akerboom

The packages.Load(nil, "std") call executes the go list command and parses the output. I note this for others who might also make the incorrect assumption that the package provides the command implementation. – Perky

Answer 2

Use the go list std command to list the standard packages. The special import path std expands to all packages in the standard Go library (doc).

Exec that command to get the list in a Go program:

cmd := exec.Command("go", "list", "std")
p, err := cmd.Output()
if err != nil {
    // handle error
}
stdPkgs = strings.Fields(string(p))

Cresa

Answer 3

If you want a simple solution, you could check if a package is present in $GOROOT/pkg. All standard packages are installed here.

Buie