Trying to parse a stdout on command line with Golang - parsing

Question

I'm practicing to use GoLang to pass arguements to the command line, and being able to parse information from the results that are passed out. For example, I have code that is designed to execute a command, and display what will display anyway if the command was entered through cmd anyway.
package main
import (
"bytes"
"fmt"
"os"
"os/exec"
"strings"
)
func main() {
cmd = exec.Command("ping", "8.8.8.8")
cmdOutput = &bytes.Buffer{}
cmd.Stdout = cmdOutput
printCommand(cmd)
err = cmd.Run()
printError(err)
printOutput(cmdOutput.Bytes())
}
func printCommand(cmd *exec.Cmd) {
fmt.Printf("==> Executing: %s\n", strings.Join(cmd.Args, " "))
}
func printError(err error) {
if err != nil {
os.Stderr.WriteString(fmt.Sprintf("==> Error: %s\n", err.Error()))
}
}
func printOutput(outs []byte) {
if len(outs) > 0 {
fmt.Printf("==> Output: %s\n", string(outs))
}
}
Considering the output would be:
==> Executing: ping 8.8.8.8
==> Output:
Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=13ms TTL=56
Reply from 8.8.8.8: bytes=32 time=13ms TTL=56
Reply from 8.8.8.8: bytes=32 time=14ms TTL=56
Reply from 8.8.8.8: bytes=32 time=11ms TTL=56
Ping statistics for 8.8.8.8:
Packets: Sent = 4, Received = 4, Lost = 0 (0% lo
Approximate round trip times in milli-seconds:
Minimum = 11ms, Maximum = 14ms, Average = 12ms
My question is: If I wanted to parse the Average response time, so I can assign that to a variable so I can display that when I want to, how can I parse that?

Answer 1

You can use regexp. For instance something like:
package main
import (
"bytes"
"fmt"
"os"
"os/exec"
"regexp"
"strings"
"time"
)
type Ping struct {
average time.Duration
}
func main() {
cmd := exec.Command("ping", "8.8.8.8")
// Linux version
//cmd := exec.Command("ping", "-c 4", "8.8.8.8")
cmdOutput := &bytes.Buffer{}
cmd.Stdout = cmdOutput
printCommand(cmd)
err := cmd.Run()
printError(err)
output := cmdOutput.Bytes()
printOutput(output)
ping := Ping{}
parseOutput(output, &ping)
fmt.Println(ping)
}
func printCommand(cmd *exec.Cmd) {
fmt.Printf("==> Executing: %s\n", strings.Join(cmd.Args, " "))
}
func printError(err error) {
if err != nil {
os.Stderr.WriteString(fmt.Sprintf("==> Error: %s\n", err.Error()))
}
}
func printOutput(outs []byte) {
if len(outs) > 0 {
fmt.Printf("==> Output: %s\n", string(outs))
}
}
func parseOutput(outs []byte, ping *Ping) {
var average = regexp.MustCompile(`Average = (\d+ms)`)
result := average.FindStringSubmatch(string(outs))
if len(result) > 0 {
ping.average, _ = time.ParseDuration(result[1])
}
// Linux version
/*var average = regexp.MustCompile(`min\/avg\/max\/mdev = (0\.\d+)\/(0\.\d+)\/(0\.\d+)\/(0\.\d+) ms`)
result := average.FindAllStringSubmatch(string(outs), -1)
if len(result) > 0 {
ping.average, _ = time.ParseDuration(result[0][2] + "ms")
}*/
}