diff --git a/complete.go b/complete.go
index 8ee823d..6d5bc16 100644
--- a/complete.go
+++ b/complete.go
@@ -183,7 +183,7 @@ func (o *opCompleter) CompleteRefresh() {
 			colWidth = w
 		}
 	}
-	colNum := getWidth() / (colWidth + o.candidateOff + 2)
+	colNum := getWidth(o.op.cfg.StdoutFd) / (colWidth + o.candidateOff + 2)
 	o.candidateColNum = colNum
 	buf := bytes.NewBuffer(nil)
 	buf.Write(bytes.Repeat([]byte("\n"), lineCnt))
diff --git a/operation.go b/operation.go
index ffb3fe3..5842480 100644
--- a/operation.go
+++ b/operation.go
@@ -58,7 +58,7 @@ func (w *wrapWriter) Write(b []byte) (int, error) {
 func NewOperation(t *Terminal, cfg *Config) *Operation {
 	op := &Operation{
 		t:       t,
-		buf:     NewRuneBuffer(t, cfg.Prompt, cfg.MaskRune),
+		buf:     NewRuneBuffer(t, cfg.Prompt, cfg.MaskRune, cfg),
 		outchan: make(chan []rune),
 		errchan: make(chan error),
 	}
@@ -392,11 +392,12 @@ func (op *Operation) SetConfig(cfg *Config) (*Config, error) {
 	op.cfg = cfg
 	op.SetPrompt(cfg.Prompt)
 	op.SetMaskRune(cfg.MaskRune)
+	op.buf.SetConfig(cfg)
 
 	if cfg.opHistory == nil {
 		op.SetHistoryPath(cfg.HistoryFile)
 		cfg.opHistory = op.history
-		cfg.opSearch = newOpSearch(op.buf.w, op.buf, op.history)
+		cfg.opSearch = newOpSearch(op.buf.w, op.buf, op.history, cfg)
 	}
 	op.history = cfg.opHistory
 
diff --git a/readline.go b/readline.go
index 4069b03..04ddf13 100644
--- a/readline.go
+++ b/readline.go
@@ -47,12 +47,20 @@ type Config struct {
 
 	UniqueEditLine bool
 
+	// force use interactive even stdout is not a tty
+	StdoutFd            int
+	ForceUseInteractive bool
+
 	// private fields
 	inited    bool
 	opHistory *opHistory
 	opSearch  *opSearch
 }
 
+func (c *Config) useInteractive() bool {
+	return c.ForceUseInteractive || IsTerminal(c.StdoutFd)
+}
+
 func (c *Config) Init() error {
 	if c.inited {
 		return nil
@@ -67,6 +75,9 @@ func (c *Config) Init() error {
 	if c.Stderr == nil {
 		c.Stderr = Stderr
 	}
+	if c.StdoutFd == 0 {
+		c.StdoutFd = StdoutFd
+	}
 	if c.HistoryLimit == 0 {
 		c.HistoryLimit = 500
 	}
@@ -85,6 +96,12 @@ func (c *Config) Init() error {
 	return nil
 }
 
+func (c Config) Clone() *Config {
+	c.opHistory = nil
+	c.opSearch = nil
+	return &c
+}
+
 func (c *Config) SetListener(f func(line []rune, pos int, key rune) (newLine []rune, newPos int, ok bool)) {
 	c.Listener = FuncListener(f)
 }
@@ -160,8 +177,8 @@ func (i *Instance) Readline() (string, error) {
 	return i.Operation.String()
 }
 
-func (i *Instance) SaveHistory(content string) {
-	i.Operation.SaveHistory(content)
+func (i *Instance) SaveHistory(content string) error {
+	return i.Operation.SaveHistory(content)
 }
 
 // same as readline
diff --git a/runebuf.go b/runebuf.go
index 358f3bf..e4bcc74 100644
--- a/runebuf.go
+++ b/runebuf.go
@@ -21,6 +21,8 @@ type RuneBuffer struct {
 	mask   rune
 
 	cleanInScreen bool
+	interactive   bool
+	cfg           *Config
 
 	bck *runeBufferBck
 }
@@ -39,15 +41,22 @@ func (r *RuneBuffer) Restore() {
 	})
 }
 
-func NewRuneBuffer(w io.Writer, prompt string, mask rune) *RuneBuffer {
+func NewRuneBuffer(w io.Writer, prompt string, mask rune, cfg *Config) *RuneBuffer {
 	rb := &RuneBuffer{
-		w:    w,
-		mask: mask,
+		w:           w,
+		mask:        mask,
+		interactive: cfg.useInteractive(),
+		cfg:         cfg,
 	}
 	rb.SetPrompt(prompt)
 	return rb
 }
 
+func (r *RuneBuffer) SetConfig(cfg *Config) {
+	r.cfg = cfg
+	r.interactive = cfg.useInteractive()
+}
+
 func (r *RuneBuffer) SetMask(m rune) {
 	r.mask = m
 }
@@ -276,7 +285,7 @@ func (r *RuneBuffer) MoveToLineEnd() {
 }
 
 func (r *RuneBuffer) LineCount() int {
-	return LineCount(runes.WidthAll(r.buf) + r.PromptLen())
+	return LineCount(r.cfg.StdoutFd, runes.WidthAll(r.buf)+r.PromptLen())
 }
 
 func (r *RuneBuffer) MoveTo(ch rune, prevChar, reverse bool) (success bool) {
@@ -310,9 +319,9 @@ func (r *RuneBuffer) MoveTo(ch rune, prevChar, reverse bool) (success bool) {
 
 func (r *RuneBuffer) IdxLine() int {
 	totalWidth := runes.WidthAll(r.buf[:r.idx]) + r.PromptLen()
-	w := getWidth()
-	if w == 0 {
-		return 0
+	w := getWidth(r.cfg.StdoutFd)
+	if w < 0 {
+		return -1
 	}
 	line := totalWidth / w
 
@@ -332,6 +341,12 @@ func (r *RuneBuffer) CursorLineCount() int {
 }
 
 func (r *RuneBuffer) Refresh(f func()) {
+	if !r.interactive {
+		if f != nil {
+			f()
+		}
+		return
+	}
 	r.Clean()
 	if f != nil {
 		f()
@@ -424,7 +439,7 @@ func (r *RuneBuffer) cleanOutput() []byte {
 }
 
 func (r *RuneBuffer) Clean() {
-	if r.cleanInScreen {
+	if r.cleanInScreen || !r.interactive {
 		return
 	}
 	r.cleanInScreen = true
diff --git a/search.go b/search.go
index 53d9e50..1b82ae4 100644
--- a/search.go
+++ b/search.go
@@ -26,11 +26,12 @@ type opSearch struct {
 	buf       *RuneBuffer
 	data      []rune
 	history   *opHistory
+	cfg       *Config
 	markStart int
 	markEnd   int
 }
 
-func newOpSearch(w io.Writer, buf *RuneBuffer, history *opHistory) *opSearch {
+func newOpSearch(w io.Writer, buf *RuneBuffer, history *opHistory, cfg *Config) *opSearch {
 	return &opSearch{
 		w:       w,
 		buf:     buf,
@@ -123,7 +124,7 @@ func (o *opSearch) SearchRefresh(x int) {
 	}
 	x = o.buf.CurrentWidth(x)
 	x += o.buf.PromptLen()
-	x = x % getWidth()
+	x = x % getWidth(o.cfg.StdoutFd)
 
 	if o.markStart > 0 {
 		o.buf.SetStyle(o.markStart, o.markEnd, "4")
diff --git a/std.go b/std.go
index 3baf5a7..200420b 100644
--- a/std.go
+++ b/std.go
@@ -3,6 +3,7 @@ package readline
 import (
 	"io"
 	"os"
+	"sync"
 )
 
 var (
@@ -10,3 +11,35 @@ var (
 	Stdout io.WriteCloser = os.Stdout
 	Stderr io.WriteCloser = os.Stderr
 )
+
+var (
+	std     *Instance
+	stdOnce sync.Once
+)
+
+func getInstance() *Instance {
+	stdOnce.Do(func() {
+		std, _ = NewEx(&Config{
+			DisableAutoSaveHistory: true,
+		})
+	})
+	return std
+}
+
+func SetHistoryPath(fp string) {
+	ins := getInstance()
+	cfg := ins.Config.Clone()
+	cfg.HistoryFile = fp
+	ins.SetConfig(cfg)
+}
+
+func AddHistory(content string) error {
+	ins := getInstance()
+	return ins.SaveHistory(content)
+}
+
+func Line(prompt string) (string, error) {
+	ins := getInstance()
+	ins.SetPrompt(prompt)
+	return ins.Readline()
+}
diff --git a/utils.go b/utils.go
index 386bcba..6be2e38 100644
--- a/utils.go
+++ b/utils.go
@@ -87,8 +87,8 @@ func escapeKey(r rune) rune {
 }
 
 // calculate how many lines for N character
-func LineCount(w int) int {
-	screenWidth := getWidth()
+func LineCount(stdoutFd int, w int) int {
+	screenWidth := getWidth(stdoutFd)
 	r := w / screenWidth
 	if w%screenWidth != 0 {
 		r++
diff --git a/utils_unix.go b/utils_unix.go
index 7a40cff..e862507 100644
--- a/utils_unix.go
+++ b/utils_unix.go
@@ -15,15 +15,16 @@ type winsize struct {
 }
 
 // get width of the terminal
-func getWidth() int {
+func getWidth(stdoutFd int) int {
 	ws := &winsize{}
 	retCode, _, errno := syscall.Syscall(syscall.SYS_IOCTL,
-		uintptr(StdoutFd),
+		uintptr(stdoutFd),
 		uintptr(syscall.TIOCGWINSZ),
 		uintptr(unsafe.Pointer(ws)))
 
 	if int(retCode) == -1 {
-		panic(errno)
+		_ = errno
+		return -1
 	}
 	return int(ws.Col)
 }
diff --git a/utils_windows.go b/utils_windows.go
index 4cee4b6..016bb05 100644
--- a/utils_windows.go
+++ b/utils_windows.go
@@ -7,10 +7,10 @@ func init() {
 }
 
 // get width of the terminal
-func getWidth() int {
+func getWidth(fd int) int {
 	info, _ := GetConsoleScreenBufferInfo()
 	if info == nil {
-		return 0
+		return -1
 	}
 	return int(info.dwSize.x)
 }