diff --git a/index.js b/index.js
index 964254a..ca62207 100644
--- a/index.js
+++ b/index.js
@@ -2,10 +2,12 @@
 Object.defineProperty(exports, "__esModule", { value: true });
 const events_1 = require("events");
 const fs_1 = require("fs");
+const path = require("path");
 /**
  * Interval of file system polling, in milliseconds.
  */
 const PollingInterval = 100;
+const SysfsGPIOPath = "/sys/class/gpio";
 const Uint16Max = 65535;
 function parseUint16(string) {
     const n = Number.parseInt(string, 10);
@@ -78,10 +80,19 @@ class GPIOPort extends events_1.EventEmitter {
         if (!/^(in|out)$/.test(direction)) {
             throw new InvalidAccessError(`Must be "in" or "out".`);
         }
+        try {
+            await fs_1.promises.access(path.join(SysfsGPIOPath, `gpio${this.portNumber}`));
+            this._exported = true;
+        }
+        catch {
+            this._exported = false;
+        }
         try {
             clearInterval(this._timeout);
-            await fs_1.promises.writeFile(`/sys/class/gpio/export`, String(this.portNumber));
-            await fs_1.promises.writeFile(`/sys/class/gpio/gpio${this.portNumber}/direction`, direction);
+            if (!this.exported) {
+                await fs_1.promises.writeFile(path.join(SysfsGPIOPath, "export"), String(this.portNumber));
+            }
+            await fs_1.promises.writeFile(path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "direction"), direction);
             if (direction === "in") {
                 this._timeout = setInterval(this.read.bind(this), this._pollingInterval);
             }
@@ -95,7 +106,7 @@ class GPIOPort extends events_1.EventEmitter {
     async unexport() {
         clearInterval(this._timeout);
         try {
-            await fs_1.promises.writeFile(`/sys/class/gpio/unexport`, String(this.portNumber));
+            await fs_1.promises.writeFile(path.join(SysfsGPIOPath, "unexport"), String(this.portNumber));
         }
         catch (error) {
             throw new OperationError(error);
@@ -103,8 +114,11 @@ class GPIOPort extends events_1.EventEmitter {
         this._exported = false;
     }
     async read() {
+        if (!(this.exported && this.direction === "in")) {
+            throw new InvalidAccessError(`The exported must be true and value of direction must be "in".`);
+        }
         try {
-            const buffer = await fs_1.promises.readFile(`/sys/class/gpio/gpio${this.portNumber}/value`);
+            const buffer = await fs_1.promises.readFile(path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "value"));
             const value = parseUint16(buffer.toString());
             if (this._value !== value) {
                 this._value = value;
@@ -117,8 +131,11 @@ class GPIOPort extends events_1.EventEmitter {
         }
     }
     async write(value) {
+        if (!(this.exported && this.direction === "out")) {
+            throw new InvalidAccessError(`The exported must be true and value of direction must be "out".`);
+        }
         try {
-            await fs_1.promises.writeFile(`/sys/class/gpio/gpio${this.portNumber}/value`, parseUint16(value.toString()).toString());
+            await fs_1.promises.writeFile(path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "value"), parseUint16(value.toString()).toString());
         }
         catch (error) {
             throw new OperationError(error);
diff --git a/index.ts b/index.ts
index 3ddf1dc..24bd161 100644
--- a/index.ts
+++ b/index.ts
@@ -1,11 +1,14 @@
 import { EventEmitter } from "events";
 import { promises as fs } from "fs";
+import * as path from "path";
 
 /**
  * Interval of file system polling, in milliseconds.
  */
 const PollingInterval = 100;
 
+const SysfsGPIOPath = "/sys/class/gpio";
+
 const Uint16Max = 65535;
 
 function parseUint16(string: string) {
@@ -127,11 +130,23 @@ export class GPIOPort extends EventEmitter {
       throw new InvalidAccessError(`Must be "in" or "out".`);
     }
 
+    try {
+      await fs.access(path.join(SysfsGPIOPath, `gpio${this.portNumber}`));
+      this._exported = true;
+    } catch {
+      this._exported = false;
+    }
+
     try {
       clearInterval(this._timeout as any);
-      await fs.writeFile(`/sys/class/gpio/export`, String(this.portNumber));
+      if (!this.exported) {
+        await fs.writeFile(
+          path.join(SysfsGPIOPath, "export"),
+          String(this.portNumber)
+        );
+      }
       await fs.writeFile(
-        `/sys/class/gpio/gpio${this.portNumber}/direction`,
+        path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "direction"),
         direction
       );
       if (direction === "in") {
@@ -152,7 +167,10 @@ export class GPIOPort extends EventEmitter {
     clearInterval(this._timeout as any);
 
     try {
-      await fs.writeFile(`/sys/class/gpio/unexport`, String(this.portNumber));
+      await fs.writeFile(
+        path.join(SysfsGPIOPath, "unexport"),
+        String(this.portNumber)
+      );
     } catch (error) {
       throw new OperationError(error);
     }
@@ -161,9 +179,15 @@ export class GPIOPort extends EventEmitter {
   }
 
   async read() {
+    if (!(this.exported && this.direction === "in")) {
+      throw new InvalidAccessError(
+        `The exported must be true and value of direction must be "in".`
+      );
+    }
+
     try {
       const buffer = await fs.readFile(
-        `/sys/class/gpio/gpio${this.portNumber}/value`
+        path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "value")
       );
 
       const value = parseUint16(buffer.toString()) as GPIOValue;
@@ -180,9 +204,15 @@ export class GPIOPort extends EventEmitter {
   }
 
   async write(value: GPIOValue) {
+    if (!(this.exported && this.direction === "out")) {
+      throw new InvalidAccessError(
+        `The exported must be true and value of direction must be "out".`
+      );
+    }
+
     try {
       await fs.writeFile(
-        `/sys/class/gpio/gpio${this.portNumber}/value`,
+        path.join(SysfsGPIOPath, `gpio${this.portNumber}`, "value"),
         parseUint16(value.toString()).toString()
       );
     } catch (error) {