Setting absolute path does not work in Go for kubeconfig

Question

I am making a call to kubectl from with a Go module like so:

getNsCmd := cmd.NewCmd("kubectl", "--kubeconfig", "~/.kube/<kube-config-file>", "get", "ns")

It works if I set the path like this:

getNsCmd := cmd.NewCmd("kubectl", "--kubeconfig", "../../../../.kube/<kube-config-file>", "get", "ns")

I am using the Go cmd package

Currently this module lives in another repo and that's why it has to navigate up four levels. I figure this is because the command is running from the perspective of this file, but it doesn't seem like it should have to. If it's simple running it as a cli command the first one (I would think) should work.

When I run this command from the cli manually it works just fine:

$ kubectl --kubeconfig ~/.kube/<kube-config-file> get ns

score 0 · Answer 1 · answered Apr 29 '22 at 17:54

Using ~ as a shortcut is something specific to bash. ~ just grabs the user's $HOME directory, but does not work across all implementations of the shell. This is something that can be used from the terminal but not always from code (it's not shell-independent). However, go can also find the current user's home directory using os.UserHomeDir().

https://pkg.go.dev/os#UserHomeDir

Something like this should work

package main

import (
    "fmt"
    "os"
)

func main() {

    homeDir, _ := os.UserHomeDir()

    fmt.Printf("%s/.kube/<kube-config-file>", homeDir)
}

Output: /root/.kube/<kube-config-file>

Unfortunately I can't comment on the reply from OP due to my low reputation score :/ But I wanted to point out that, while this might not be a concern depending on your use case for the code, getting the HOME environment variable doesn't always work with Windows, which often uses `%USERPROFILE%`. The `os.UserHomeDir` function is both shell and platform-agnostic, so will work cross-platform. @Tariq — logyball, Apr 29 '22 at 20:45

score 0 · Answer 2 · answered Apr 29 '22 at 17:56

Since the package you're using mentions that it wraps the Go's os/exec package, here is an excerpt from their documentation:

Unlike the "system" library call from C and other languages, the os/exec package intentionally does not invoke the system shell and does not expand any glob patterns or handle other expansions, pipelines, or redirections typically done by shells. The package behaves more like C's "exec" family of functions. To expand glob patterns, either call the shell directly, taking care to escape any dangerous input, or use the path/filepath package's Glob function. To expand environment variables, use package os's ExpandEnv.

So I think you would want to try something like this:

import "os"

getNsCmd := cmd.NewCmd("kubectl", "--kubeconfig", os.ExpandEnv("$HOME/.kube/<kube-config-file>"), "get", "ns")

score 0 · Accepted Answer · answered Apr 29 '22 at 19:02

As others have mentioned I needed to grab the home directory environment var. However I implemented it like this:

    homePath, _ := os.LookupEnv("HOME")

//

getNsCmd := cmd.NewCmd("kubectl", "--kubeconfig", homePath+"/.kube/<kube-config-file>", "get", "ns")

Setting absolute path does not work in Go for kubeconfig

3 Answers3