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// +build !windows,!plan9
package os
import (
"bytes"
"os"
"os/exec"
"regexp"
"strings"
)
var reValidHostname = regexp.MustCompile(`^([0-9a-zA-Z-]+\.)[0-9a-zA-Z-]+$`)
func machineFQDN() (string, error) {
hn, err := os.Hostname()
if err != nil {
return "", err
}
hn = strings.TrimSuffix(hn, ".")
n := strings.Count(hn, ".")
if n > 0 {
return hn, nil
}
buf := bytes.Buffer{}
cmd := exec.Command("hostname", "-f")
cmd.Stdout = &buf
err = cmd.Run()
if err != nil {
return hn, err
}
fqdn := strings.TrimSuffix(strings.TrimSpace(buf.String()), ".")
if !reValidHostname.MatchString(fqdn) || strings.Count(fqdn, ".") < n {
return hn, nil
}
return fqdn, nil
}
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