How to connect xml decoder to stdoutPipe() of go exec - go

Question

I'm having some trouble linking things up here.
What am I doing incorrectly?
package main
import (
"encoding/xml"
"fmt"
"log"
"os/exec"
)
func checkError(err error) {
if err != nil {
log.Fatalf("Error: %s", err)
}
}
func metrics() {
cmd := exec.Command(
"nvidia-smi",
"--query",
"--xml-format")
out, err := cmd.StdoutPipe()
checkError(err)
cmd.Start()
defer cmd.Wait()
go func() {
var data interface{}
dec := xml.NewDecoder(out)
dec.Decode(&data)
fmt.Printf("Data: %+v\n", data)
}()
//go io.Copy(os.Stdout, out)
}
func main() {
metrics()
}
Result after running program is:
Data:

Answer 1

Things seem to be "linked" correctly.
Problem is likely to be here:
var data interface{}
You then do:
dec.Decode(&data)
But that won't work.
You need to pass in a struct that can actually be used to decode the fields in the XML that the nvidia-smi command returns.
Find below a modified example (replacing your nvidia-smi for an echo command to make it return a sample XML).
You should adjust the struct to be able to map to the actual XML you'll receive.
By the way:
You should check the error returned by decode just in case
I don't understand why you are decoding in a separate goroutine. I left it like that in the modified example, but it would work if you do it right in the same goroutine as well.
Example:
package main
import (
"log"
"os/exec"
"fmt"
"encoding/xml"
)
func checkError(err error) {
if err != nil {
log.Fatalf("Error: %s", err)
}
}
type Result struct {
Value int `xml:"value"`
}
func metrics() {
cmd := exec.Command(
"echo", "-n",
`<result><value>1</value></result>`)
out, err := cmd.StdoutPipe()
checkError(err)
cmd.Start()
defer cmd.Wait()
go func() {
var data Result
dec := xml.NewDecoder(out)
err = dec.Decode(&data)
checkError(err)
fmt.Printf("Data: %+v\n", data)
}()
//go io.Copy(os.Stdout, out)
}
func main() {
metrics()
}