Unset an environment variable

[Larry Clapp]

Hi, Gophers.

I see how to set and query individual environment variables.  I see you can clear the entire environment.  Is there nothing in the standard library to unset a single variable?  Do I really have to copy the environment, clear it, and then reset everything but the thing I want unset?

</whine>  :)

-- Larry

[Ian Lance Taylor]

On Fri, Sep 19, 2014 at 12:56 PM, Larry Clapp <la...@theclapp.org> wrote:
>
> I see how to set and query individual environment variables. I see you can
> clear the entire environment. Is there nothing in the standard library to
> unset a single variable? Do I really have to copy the environment, clear
> it, and then reset everything but the thing I want unset?

http://golang.org/issue/6423

Ian

[Larry Clapp]

Thank you, I did not think to search for an existing issue.

Nor did I think of filtering the environment directly when forking, as mentioned in the issue.

Sorry for the whine.

For posterity, this worked for me, though it does suffer from the same race condition mentioned in the linked issue: some other thread could read the environment after you've cleared it and and before you repopulate it.

func Unsetenv(key string) {
   if _, found := syscall.Getenv(key); !found {
      return
   }
   env := os.Environ()
   os.Clearenv()
   for _, s := range env {
      for j := 0; j < len(s); j++ {
         if s[j] == '=' {
            k := s[:j]
            if key == k {
               break
            }
            os.Setenv(k, s[j+1:])
         }
      }
   }
}

-- Larry