diff --git a/cli.js b/cli.js
index e7c7c7a..7a13be2 100755
--- a/cli.js
+++ b/cli.js
@@ -82,7 +82,7 @@ const executeString = (args, port, dataConsumer) => {
   const code = args[0] || ''
   return board.open(port)
   .then(() => board.enter_raw_repl())
-  .then(() => board.exec_raw({ command: code, data_consumer: dataConsumer }))
+  .then(() => board.exec_raw(code, dataConsumer))
   .then(async (out) => {
     await board.exit_raw_repl()
     await board.close()
diff --git a/micropython.js b/micropython.js
index 173f67b..5bec72b 100644
--- a/micropython.js
+++ b/micropython.js
@@ -210,6 +210,7 @@ class MicroPythonBoard {
         command += `  print(1)\n`
         command += `except OSError:\n`
         command += `  print(0)\n`
+        command += `del f\n`
     await this.enter_raw_repl()
     let output = await this.exec_raw(command)
     await this.exit_raw_repl()
@@ -240,11 +241,13 @@ class MicroPythonBoard {
     let command = `import uos\n`
         command += `try:\n`
         command += `  l=[]\n`
-        command += `  for file in uos.ilistdir("${folderPath}"):\n`
-        command += `    l.append(list(file))\n`
+        command += `  for f in uos.ilistdir("${folderPath}"):\n`
+        command += `    l.append(list(f))\n`
         command += `  print(l)\n`
         command += `except OSError:\n`
         command += `  print([])\n`
+        command += `del l\n`
+        command += `del f\n`
     await this.enter_raw_repl()
     let output = await this.exec_raw(command)
     await this.exit_raw_repl()
@@ -259,9 +262,16 @@ class MicroPythonBoard {
   async fs_cat_binary(filePath) {
     if (filePath) {
       await this.enter_raw_repl()
-      let output = await this.exec_raw(
-        `with open('${filePath}','rb') as f:\n while 1:\n  b=f.read(256)\n  if not b:break\n  print(",".join(str(e) for e in b),end=',')`
-      )
+      const chunkSize = 256
+      let command =  `with open('${filePath}','rb') as f:\n`
+          command += `  while 1:\n`
+          command += `    b=f.read(${chunkSize})\n`
+          command += `    if not b:break\n`
+          command += `    print(",".join(str(e) for e in b),end=',')\n`
+          command += `del f\n`
+          command += `del b\n`
+      let output = await this.exec_raw(command)
+      
       await this.exit_raw_repl()
       output = extractBytes(output, 2, 4)
       return Promise.resolve((output))
@@ -273,7 +283,7 @@ class MicroPythonBoard {
     if (filePath) {
       await this.enter_raw_repl()
       let output = await this.exec_raw(
-        `with open('${filePath}','r') as f:\n while 1:\n  b=f.read(256)\n  if not b:break\n  print(b,end='')`
+        `with open('${filePath}','r') as f:\n while 1:\n  b=f.read(256)\n  if not b:break\n  print(b,end='')\ndel f\ndel b\n`
       )
       await this.exit_raw_repl()
       output = extract(output)
@@ -297,7 +307,7 @@ class MicroPythonBoard {
         out += await this.exec_raw(line)
         data_consumer( parseInt((i / contentBuffer.length) * 100) + '%')
       }
-      out += await this.exec_raw(`f.close()`)
+      out += await this.exec_raw(`f.close()\ndel f\ndel w\n`)
       out += await this.exit_raw_repl()
       return Promise.resolve(out)
     }
@@ -318,7 +328,7 @@ class MicroPythonBoard {
         out += await this.exec_raw(line)
         data_consumer( parseInt((i / contentBuffer.length) * 100) + '%')
       }
-      out += await this.exec_raw(`f.close()`)
+      out += await this.exec_raw(`f.close()\ndel f\ndel w\n`)
       out += await this.exit_raw_repl()
       return Promise.resolve(out)
     } else {
diff --git a/package-lock.json b/package-lock.json
index beab231..b5256b3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "micropython.js",
-  "version": "1.4.4",
+  "version": "1.5.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "micropython.js",
-      "version": "1.4.4",
+      "version": "1.5.1",
       "dependencies": {
         "serialport": "^10.4.0"
       },
diff --git a/package.json b/package.json
index e554810..62cae7b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "micropython.js",
-  "version": "1.5.0",
+  "version": "1.5.1",
   "description": "Interpretation of pyboard.py in javascript",
   "main": "micropython.js",
   "scripts": {