Restructure packages for reuse

internal/command/command.go

@@ -0,0 +1,32 @@
+package command
+
+import (
+	"os/exec"
+	"runtime"
+
+	"golang.org/x/sys/unix"
+)
+
+// Run runs an OS command.  On Linux it waits for the command to
+// complete and returns the exit status (return code).
+func Run(name string, arg ...string) (string, int, error) {
+	cmd := exec.Command(name, arg...)
+	// Run the command and wait for completion
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		var rc int
+		// Only works on Linux
+		if runtime.GOOS == "linux" {
+			var ws unix.WaitStatus
+			unix.Wait4(cmd.Process.Pid, &ws, 0, nil)
+			rc = ws.ExitStatus()
+		} else {
+			rc = -1
+		}
+		if rc == 0 {
+			return string(out), rc, nil
+		}
+		return string(out), rc, err
+	}
+	return string(out), 0, nil
+}