Getting Python version using Go

I’m trying to get my Python version using Go:

import (
    "log"
    "os/exec"
    "strings"
)

func verifyPythonVersion() {
    _, err := exec.LookPath("python")
    if err != nil {
        log.Fatalf("No python version located")

    }
    out, err := exec.Command("python", "--version").Output()
    log.Print(out)
    if err != nil {
        log.Fatalf("Error checking Python version with the 'python' command: %v", err)
    }
    fields := strings.Fields(string(out))
    log.Print(fields)

}

func main() {
    verifyPythonVersion()
}

This returns empty slices:

2014/01/03 20:39:53 []
2014/01/03 20:39:53 []

Any idea what I’m doing wrong?

Best answer

$ python --version
Python 2.7.2
$ python --version 1>/dev/null # hide stdout
Python 2.7.2
$ python --version 2>/dev/null # hide stderr

We can conclude that the output goes to stderr. Now I took a look at Go’s docs, and guess what, cmd.Output only captures stdout (docs). You should use cmd.CombinedOutput (docs) :

CombinedOutput runs the command and returns its combined standard output and standard error.