make pkg/parsers support darwin and solaris

Signed-off-by: allencloud <allen.sun@daocloud.io>

parsers/kernel/kernel_darwin.go

@@ -0,0 +1,56 @@
+// +build darwin
+
+// Package kernel provides helper function to get, parse and compare kernel
+// versions for different platforms.
+package kernel
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/mattn/go-shellwords"
+)
+
+// GetKernelVersion gets the current kernel version.
+func GetKernelVersion() (*VersionInfo, error) {
+	release, err := getRelease()
+	if err != nil {
+		return nil, err
+	}
+
+	return ParseRelease(release)
+}
+
+// getRelease uses `system_profiler SPSoftwareDataType` to get OSX kernel version
+func getRelease() (string, error) {
+	cmd := exec.Command("system_profiler", "SPSoftwareDataType")
+	osName, err := cmd.Output()
+	if err != nil {
+		return "", err
+	}
+
+	var release string
+	data := strings.Split(string(osName), "\n")
+	for _, line := range data {
+		if strings.Contains(line, "Kernel Version") {
+			// It has the format like '      Kernel Version: Darwin 14.5.0'
+			content := strings.SplitN(line, ":", 2)
+			if len(content) != 2 {
+				return "", fmt.Errorf("Kernel Version is invalid")
+			}
+
+			prettyNames, err := shellwords.Parse(content[1])
+			if err != nil {
+				return "", fmt.Errorf("Kernel Version is invalid: %s", err.Error())
+			}
+
+			if len(prettyNames) != 2 {
+				return "", fmt.Errorf("Kernel Version needs to be 'Darwin x.x.x' ")
+			}
+			release = prettyNames[1]
+		}
+	}
+
+	return release, nil
+}