diff --git a/global.go b/global.go
new file mode 100644
index 0000000..41d7292
--- /dev/null
+++ b/global.go
@@ -0,0 +1,87 @@
+package log
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
+
+func GetLogid() string {
+	if logidCreator != nil {
+		return logidCreator.GetLogid()
+	}
+	return ""
+}
+
+func SetLogid(logid string) {
+	if logidCreator != nil {
+		logidCreator.SetLogid(logid)
+	}
+}
+
+func Cleanup() {
+	if logidCreator != nil {
+		logidCreator.Cleanup()
+	}
+}
+
+func SetLogLevel(newlv logLevel) (oldlv logLevel) {
+	return mylog.SetLogLevel(newlv)
+}
+
+func PrintPretty(prefix string, v interface{}) {
+	mylog.PrintPretty(prefix, v)
+}
+
+func DebugfWithDepth(calldepth int, format string, v ...interface{}) {
+	mylog.DebugfWithDepth(calldepth, format, v...)
+}
+
+func Debugf(format string, v ...interface{}) {
+	mylog.Debugf(format, v...)
+}
+
+func Noticef(format string, v ...interface{}) {
+	mylog.Noticef(format, v...)
+}
+
+func NoticefWithDepth(calldepth int, format string, v ...interface{}) {
+	mylog.NoticefWithDepth(calldepth, format, v...)
+}
+
+func Infof(format string, v ...interface{}) {
+	mylog.Infof(format, v...)
+}
+
+func Warningf(format string, v ...interface{}) {
+	mylog.Warningf(format, v...)
+}
+
+func Errorf(format string, v ...interface{}) {
+	mylog.Warningf(format, v...)
+}
+
+func Panicf(format string, v ...interface{}) {
+	mylog.Panicf(format, v...)
+}
+
+func Fatalf(format string, v ...interface{}) {
+	mylog.Fatalf(format, v...)
+}
+
+func TraceInto(format string, v ...interface{}) string {
+	_, fn, line, _ := runtime.Caller(1)
+	strfn := fmt.Sprintf("%s:%d", fn, line)
+	Debugf("TRACE into ["+strfn+"]"+format+"...\r\n", v...)
+
+	return strfn
+}
+
+func TraceExit(strfn string, format string, v ...interface{}) {
+	Debugf("TRACE exit ["+strfn+"]"+format+"...\r\n", v...)
+}
+
+func RegisterLogidCreator(idc LogidCreator) {
+	logidCreator = idc
+	SetLogid(fmt.Sprintf("sysinit(%d)", os.Getpid()))
+}
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..0290adc
--- /dev/null
+++ b/util.go
@@ -0,0 +1,29 @@
+package log
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// getExeFilename
+func getExeFilename() string {
+	_, logfilename := filepath.Split(os.Args[0])
+	if logfilename == "" {
+		panic("get exe filename failed")
+	}
+	return logfilename
+}
+
+// tryOptLogDirs
+func tryOptLogDirs(optLogDirs []string) (string, error) {
+	optionDirsStr := ""
+	for i, d := range optLogDirs {
+		dir := fmt.Sprintf("%s/", d)
+		optionDirsStr += fmt.Sprintf("%d.[%s];", i, dir)
+		if _, err := os.Stat(dir); err == nil {
+			return dir, nil
+		}
+	}
+	return "", fmt.Errorf("all optional dir are not exist: %s", optionDirsStr)
+}
diff --git a/writer.go b/writer.go
new file mode 100644
index 0000000..2b30b54
--- /dev/null
+++ b/writer.go
@@ -0,0 +1,134 @@
+package log
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+type baseWriter struct {
+	logw *os.File
+	stdw *os.File
+	errw *os.File
+
+	logFilename     string
+	logPreBackupTag string
+}
+
+type cacheWriter struct {
+	cache      bytes.Buffer
+	cacheing   bool
+	cacheLock  *sync.Mutex
+	baseWriter io.Writer
+}
+
+func NewBaseWriter(logw, stdw, errw *os.File) *baseWriter {
+	return &baseWriter{
+		logw: logw,
+		stdw: stdw,
+		errw: errw,
+	}
+}
+
+// OpenLogFile
+func (w *baseWriter) OpenLogFile(logDir, logName string, optLogDirs []string) {
+	// Step 1. try get available log dir
+	if _, err := os.Stat(logDir); err == nil {
+		logDir = logDir
+	} else if dir, err := tryOptLogDirs(optLogDirs); err == nil {
+		logDir = dir
+	} else if err := os.Mkdir(logDir, 0755); err == nil {
+		logDir = logDir
+	} else {
+		errstr := fmt.Sprintf("all path not exist:\n "+
+			"a.[%s]\n b.[%s]\n c.[%s]\n",
+			logDir, "./log/", "./logs/")
+		panic("failed initlog:" + errstr)
+	}
+
+	// Step 2. open base writer logfile
+	filename := filepath.Join(logDir, logName+".log")
+	w.logFilename = filename
+	w.logPreBackupTag = ""
+	w.ReopenLogFile()
+}
+
+// ReopenLogFile
+func (w *baseWriter) ReopenLogFile() {
+	var fil, err = os.OpenFile(w.logFilename,
+		os.O_APPEND|os.O_CREATE|os.O_WRONLY, os.ModePerm)
+	if err != nil {
+		panic("open log file failed:" + err.Error())
+	}
+	w.logw.Close()
+	w.logw = fil
+}
+
+// BackupLogFile
+func (w *baseWriter) TryBackupLogFile(tag string) bool {
+	if w.logPreBackupTag == "" {
+		w.logPreBackupTag = tag
+		return false
+	} else if w.logPreBackupTag == tag {
+		return false
+	}
+
+	w.logPreBackupTag = tag
+	newname := w.logFilename + "." + tag
+	if err := os.Rename(w.logFilename, newname); err != nil {
+		return false
+	}
+
+	w.ReopenLogFile()
+	return true
+}
+
+func NewCacheWriter(basewriter io.Writer) *cacheWriter {
+	return &cacheWriter{
+		cache:      bytes.Buffer{},
+		cacheing:   false,
+		cacheLock:  new(sync.Mutex),
+		baseWriter: basewriter,
+	}
+}
+
+func (w *baseWriter) Write(p []byte) (n int, err error) {
+	if w.errw != nil {
+		n, err = w.errw.Write(p)
+	}
+	if w.stdw != nil {
+		n, err = w.stdw.Write(p)
+	}
+	if w.logw != nil {
+		n, err = w.logw.Write(p)
+	}
+	return n, err
+}
+
+func (w *cacheWriter) Write(p []byte) (n int, err error) {
+	if w.cacheing {
+		w.cache.Write(p)
+	}
+	return w.baseWriter.Write(p)
+}
+
+func (w *cacheWriter) GetCacheLog() string {
+	if w.cacheing != true {
+		panic("GetCacheLog MUST call after StartCacheLog called")
+	}
+	return w.cache.String()
+}
+
+func (w *cacheWriter) StartCacheLog() {
+	w.cacheLock.Lock()
+	w.cacheing = true
+	w.cache.Reset()
+}
+
+func (w *cacheWriter) StopCacheLog() {
+	w.cacheLock.Unlock()
+	w.cacheing = true
+}