## Call type:呼叫類型：
`StorageFile.read(len)`
## 參數
`len` - 讀取多少字節
## 返回
A String, or undefined
一個 String 或未定義
## 描述
從文件中讀取“len”字節的數據，并返回一個包含這些字節的字符串。
如果到達文件末尾，返回的字符串可能會小于請求的字節數，或者如果文件已經處于末尾，則返回`undefined`。
**注意：** 這在閃存不足的設備中不可用
- Espruino簡介
- API
- 全局Globals
- acceleration()
- analogRead(pin)
- analogWrite(pin, value, options)
- atob(base64Data)
- btoa(binaryData)
- changeInterval(id, time)
- clearInterval(id)
- clearTimeout(id)
- clearWatch(id)
- compass()
- decodeURIComponent(str)
- digitalPulse(pin, value, time)
- digitalRead(pin)
- digitalWrite(pin, value)
- dump()
- echo(echoOn)
- edit(funcName)
- encodeURIComponent(str)
- eval(code)
- getPinMode(pin)
- getSerial()
- getTime()
- isFinite(x)
- isNaN(x)
- load(filename)
- parseFloat(string)
- parseInt(string, radix)
- peek16(addr, count)
- peek32(addr, count)
- peek8(addr, count)
- pinMode(pin, mode, automatic)
- poke16(addr, value)
- poke32(addr, value)
- poke8(addr,value)
- print(text, ...)
- require(moduleName)
- reset(clearFlash)
- save()
- setBusyIndicator(pin)
- setDeepSleep(sleep)
- setInterval(function, timeout, args, ...)
- setSleepIndicator(pin)
- setTime(time)
- setTimeout(function, timeout, args, ...)
- setWatch(function, pin, options)
- shiftOut(pins, options, data)
- show(image)
- trace()
- ESP8266
- ESP8266.crc32
- ESP8266.deepSleep
- ESP8266.dumpSocketInfo
- ESP8266.getFreeFlash
- ESP8266.getResetInfo
- ESP8266.getState
- ESP8266.logDebug
- ESP8266.neopixelWrite
- ESP8266.ping
- ESP8266.printLog
- ESP8266.readLog
- ESP8266.reboot
- ESP8266.setCPUFreq
- ESP8266.setLog
- ESP32
- ESP32.deepSleep(us)
- ESP32.deepSleepExt0(pin, level)
- ESP32.deepSleepExt1(pinVar, mode)
- ESP32.enableBLE(enable)
- ESP32.enableWifi(enable)
- ESP32.getState()
- ESP32.getWakeupCause()
- ESP32.reboot()
- ESP32.setAtten(pin, atten)
- ESP32.setBLE_Debug(level)
- ESP32.setOTAValid(isValid)
- Wifi
- event associated
- event auth_change
- Wifi.connect(ssid, options, callback)
- event connected
- event dhcp_timeout
- Wifi.disconnect(callback)
- event disconnected
- Wifi.getAPDetails(callback)
- Wifi.getAPIP(callback)
- Wifi.getDetails(callback)
- Wifi.getHostByName(hostname, callback)
- Wifi.getIP(callback)
- Wifi.getStatus(callback)
- Wifi.ping(hostname, callback)
- event probe_recv
- Wifi.restore()
- Wifi.save(what)
- Wifi.scan(callback)
- Wifi.setAPIP(settings, callback)
- Wifi.setConfig(settings)
- Wifi.setHostname(hostname, callback)
- Wifi.setIP(settings, callback)
- Wifi.setSNTP(server, tz_offset)
- event sta_joined
- event sta_left
- Wifi.startAP(ssid, options, callback)
- Wifi.stopAP(callback)
- Wifi.turbo(enable, callback)
- Modules
- Modules.addCached(id, sourcecode)
- Modules.getCached()
- Modules.removeAllCached()
- Modules.removeCached(id)
- Flash
- Flash.erasePage(addr)
- Flash.getFree()
- Flash.getPage(addr)
- Flash.read(length, addr)
- Flash.write(data, addr)
- Storage
- Storage.compact(showMessage)
- Storage.debug()
- Storage.erase(name)
- Storage.eraseAll()
- Storage.getFree(checkInternalFlash)
- Storage.getStats(checkInternalFlash)
- Storage.hash(regex)
- Storage.list(regex, filter)
- Storage.open(name, mode)
- Storage.optimise()
- Storage.read(name, offset, length)
- Storage.readArrayBuffer(name)
- Storage.readJSON(name, noExceptions)
- Storage.write(name, data, offset, size)
- Storage.writeJSON(name, data)
- StorageFile
- StorageFile.erase()
- StorageFile.getLength()
- StorageFile.pipe(destination, options)
- StorageFile.read(len)
- StorageFile.readLine()
- StorageFile.write(data)
- 模塊 Modules
- 使用模塊進行工作
- 內置模塊
- Espruino 模塊
- 來自 Github（或互聯網上的任何地方）
- 從 Storage 加載模塊
- 從 NPM 加載模塊
- 從一個本地文件夾
- 從 SD 卡 加載模塊
- 從互聯網加載模塊
- 已有模塊
- 常見問題
- 編寫和提交模塊(或更改)