Golang SIGSEGV仅在“第二次”通话中

Question

I have a method to quickly run a shell command:

func runcmd(c string, arg ...string) (string, string, string) {
    var o bytes.Buffer
    var e bytes.Buffer
    cmd := exec.Command(c, arg...)
    cmd.Stdout = &o
    cmd.Stderr = &e
    err := cmd.Run()
    return o.String(), e.String(), err.Error()
}

In my main have the following code:

func main() {

ver, _, exitcode := runcmd("rpm", "-q", "--queryformat", "%{VERSION}", "redhat-release")
var dist string
if exitcode != "" {
    ver, _, exitcode = runcmd("rpm", "-q", "--queryformat", "%{VERSION}", "centos-release")
    if exitcode != "" {
        fmt.Println("Unknown OS! Exiting without running!")
        os.Exit(3)
    }
    dist = "CentOS"
} else {
    dist = "Redhat/Redhat derivative"
}

fmt.Printf("System is %s %s.
", dist, ver)
}

Running this produces a SIGSEGV. However, when I comment the second call to runcmd it runs as normal (returning Unknown OS! Exiting without running! exit status 3). I'm new to go so i don't really understand the nil pointer dereference error to begin with, much less why it would only happen on the second call.

Answer 1

You are always returning err.Error(), when there is no error (err == nil) this fails with nil pointer dereference. You should do

func runcmd(c string, arg ...string) (string, string, error) {
  e bytes.Buffer
  cmd := exec.Command(c, arg...)
  cmd.Stdout = &o
  cmd.Stderr = &e
  err := cmd.Run()
  return o.String(), e.String(), err
}

and then

if exitcode != nil {