diff --git a/docs/api.md b/docs/api.md
index 1be2595..907eb0f 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -8,6 +8,7 @@
   - [Worker.remove](#worker-remove)
   - [Worker.transcode](#worker-transcode)
   - [Worker.trim](#worker-trim)
+  - [Worker.concatDemuxer](#worker-concatDemuxer)
   - [Worker.run](#worker-run)
 
 ---
@@ -135,14 +136,14 @@ Worker.remove() removes files in file system, it will be better to delete unused
 
 <a name="worker-transcode"></a>
 
-### Worker.transcode(inputPath, outputPath, options, del, jobId): Promise
+### Worker.transcode(input, output, options, del, jobId): Promise
 
 Worker.transcode() transcode a video file to another format.
 
 **Arguments:**
 
-- `inputPath` input file path, the input file should be written through Worker.write()
-- `outputPath` output file path, can be read with Worker.read() later
+- `input` input file path, the input file should be written through Worker.write()
+- `output` output file path, can be read with Worker.read() later
 - `options` a string to add extra arguments to ffmpeg
 - `del` a boolean to determine whether to delete input file after the task is done, default: true
 - `jobId` check Worker.load()
@@ -157,7 +158,7 @@ Worker.transcode() transcode a video file to another format.
 
 <a name="worker-trim"></a>
 
-### Worker.trim(inputPath, outputPath, from, to, options, del, jobId): Promise
+### Worker.trim(input, output, from, to, options, del, jobId): Promise
 
 Worker.trim() trims video to specific interval.
 
@@ -181,14 +182,14 @@ Worker.trim() trims video to specific interval.
 
 <a name="worker-concatDemuxer"></a>
 
-### Worker.concatDemuxer(inputPaths, outputPath, options, del, jobId): Promise
+### Worker.concatDemuxer(input, output, options, del, jobId): Promise
 
 Worker.concatDemuxer() concatenates multiple videos using concatDemuxer. This method won't encode the videos again. But it has its limitations. See [Concat demuxer Wiki](https://trac.ffmpeg.org/wiki/Concatenate)
 
 **Arguments:**
 
-- `inputPaths` input file paths as an Array, the input files should be written through Worker.write()
-- `outputPath` output file path, can be read with Worker.read() later
+- `input` input file paths as an Array, the input files should be written through Worker.write()
+- `output` output file path, can be read with Worker.read() later
 - `options` a string to add extra arguments to ffmpeg
 - `del` a boolean to determine whether to delete input file after the task is done, default: true
 - `jobId` check Worker.load()
@@ -197,7 +198,7 @@ Worker.concatDemuxer() concatenates multiple videos using concatDemuxer. This me
 
 ```javascript
 (async () => {
-  await worker.trim(["flame-1.avi", "flame-2.avi"], "output.mp4");
+  await worker.concatDemuxer(["flame-1.avi", "flame-2.avi"], "output.mp4");
 })();
 ```
 
@@ -210,7 +211,10 @@ Worker.run() is similar to FFmpeg cli tool, aims to provide maximum flexiblity f
 **Arguments:**
 
 - `args` a string to represent arguments, note: inputPath must start with `/data/` as worker.write write to this path by default.
-- `options` a object to define the value for inputPath, outputPath and del.
+- `options` a object to define the value for input, output and del.
+  - `input` a string or an array of strings to indicate input files, ffmpeg.js deletes these files for you.
+  - `output` a string or an array of strings to indicate output files, ffmpeg.js moves these files to `/data`, deletes them from MEMFS and you can read them with Worker.read()
+  - `del` a boolean to determine whether to delete input file after the task is done, default: true
 - `jobId` check Worker.load()
 
 **Examples:**
@@ -218,8 +222,8 @@ Worker.run() is similar to FFmpeg cli tool, aims to provide maximum flexiblity f
 ```javascript
 (async () => {
   await worker.run("-i /data/flame.avi -s 1920x1080 output.mp4", {
-    inputPath: "flame.avi",
-    outputPath: "output.mp4"
+    input: "flame.avi",
+    output: "output.mp4"
   });
 })();
 ```
diff --git a/examples/browser/image2video.html b/examples/browser/image2video.html
index 76bfb64..831a3dd 100644
--- a/examples/browser/image2video.html
+++ b/examples/browser/image2video.html
@@ -38,7 +38,7 @@
           await worker.write(`tmp.${num}.png`, `../../tests/assets/triangle/tmp.${num}.png`);
         }
         message.innerHTML = 'Start transcoding';
-        await worker.run('-framerate 30 -pattern_type glob -i /data/*.png -i /data/audio.ogg -c:a copy -shortest -c:v libx264 -pix_fmt yuv420p out.mp4', { outputPath: 'out.mp4' });
+        await worker.run('-framerate 30 -pattern_type glob -i /data/*.png -i /data/audio.ogg -c:a copy -shortest -c:v libx264 -pix_fmt yuv420p out.mp4', { output: 'out.mp4' });
         const { data } = await worker.read('out.mp4');
         await worker.remove('audio.ogg');
         for (let i = 0; i < 60; i += 1) {
diff --git a/examples/browser/run.html b/examples/browser/run.html
index 565d4a0..36c1abe 100644
--- a/examples/browser/run.html
+++ b/examples/browser/run.html
@@ -33,7 +33,7 @@
         await worker.load();
         message.innerHTML = 'Start transcoding';
         await worker.write(name, files[0]);
-        await worker.run(`-i /data/${name} output.mp4`, { inputPath: name, outputPath: 'output.mp4' });
+        await worker.run(`-i /data/${name} output.mp4`, { input: name, output: 'output.mp4' });
         message.innerHTML = 'Complete transcoding';
         const { data } = await worker.read('output.mp4');
 
diff --git a/examples/browser/transcode.html b/examples/browser/transcode.html
index bf36b59..cb14c37 100644
--- a/examples/browser/transcode.html
+++ b/examples/browser/transcode.html
@@ -23,6 +23,7 @@
       const { createWorker } = FFmpeg;
       const worker = createWorker({
         corePath: '../../node_modules/@ffmpeg/core/ffmpeg-core.js',
+        logger: ({ message }) => console.log(message),
         progress: p => console.log(p),
       });
 
@@ -36,7 +37,6 @@
         await worker.transcode(name,  'output.mp4');
         message.innerHTML = 'Complete transcoding';
         const { data } = await worker.read('output.mp4');
-        console.log(data);
 
         const video = document.getElementById('output-video');
         video.src = URL.createObjectURL(new Blob([data.buffer], { type: 'video/mp4' }));
diff --git a/examples/browser/trim.html b/examples/browser/trim.html
index 1e7ade0..8d8250b 100644
--- a/examples/browser/trim.html
+++ b/examples/browser/trim.html
@@ -15,7 +15,7 @@
     </style>
   </head>
   <body>
-    <h3>Upload a mp4 (x264) video and trim its first 2 seconds and play!</h3>
+    <h3>Upload a mp4 (x264) video and trim its first 10 seconds and play!</h3>
     <video id="output-video" controls></video><br/>
     <input type="file" id="uploader">
     <p id="message"></p>
@@ -33,7 +33,7 @@
         await worker.load();
         message.innerHTML = 'Start trimming';
         await worker.write(name, files[0]);
-        await worker.trim(name,  'output.mp4', 0, 2);
+        await worker.trim(name,  'output.mp4', 0, 10);
         message.innerHTML = 'Complete trimming';
         const { data } = await worker.read('output.mp4');
 
diff --git a/examples/node/image2video.js b/examples/node/image2video.js
index d9202e6..f705f0c 100755
--- a/examples/node/image2video.js
+++ b/examples/node/image2video.js
@@ -15,7 +15,7 @@ const worker = createWorker({
     await worker.write(`tmp.${num}.png`, `../../tests/assets/triangle/tmp.${num}.png`);
   }
   console.log('Start transcoding');
-  await worker.run('-framerate 30 -pattern_type glob -i /data/*.png -i /data/audio.ogg -c:a copy -shortest -c:v libx264 -pix_fmt yuv420p out.mp4', { outputPath: 'out.mp4' });
+  await worker.run('-framerate 30 -pattern_type glob -i /data/*.png -i /data/audio.ogg -c:a copy -shortest -c:v libx264 -pix_fmt yuv420p out.mp4', { output: 'out.mp4' });
   const { data } = await worker.read('out.mp4');
   console.log('Complete transcoding');
   await worker.remove('audio.ogg');
diff --git a/examples/node/run.js b/examples/node/run.js
index c55082f..4946333 100755
--- a/examples/node/run.js
+++ b/examples/node/run.js
@@ -9,7 +9,7 @@ const worker = createWorker({
   await worker.load();
   console.log('Start transcoding');
   await worker.write('flame.avi', '../../tests/assets/flame.avi');
-  await worker.run('-i /data/flame.avi flame.mp4', { inputPath: 'flame.avi', outputPath: 'flame.mp4' });
+  await worker.run('-i /data/flame.avi flame.mp4', { input: 'flame.avi', output: 'flame.mp4' });
   const { data } = await worker.read('flame.mp4');
   console.log('Complete transcoding');
   fs.writeFileSync('flame.mp4', Buffer.from(data));
diff --git a/examples/node/trim.js b/examples/node/trim.js
index a03a9e5..d9689b7 100755
--- a/examples/node/trim.js
+++ b/examples/node/trim.js
@@ -9,7 +9,7 @@ const worker = createWorker({
   await worker.load();
   console.log('Start trimming');
   await worker.write('flame.avi', '../../tests/assets/flame.avi');
-  await worker.trim('flame.avi', 'flame_trim.avi', 1, 2);
+  await worker.trim('flame.avi', 'flame_trim.avi', 0, 10);
   const { data } = await worker.read('flame_trim.avi');
   console.log('Complete trimming');
   fs.writeFileSync('flame_trim.avi', Buffer.from(data));
diff --git a/src/createWorker.js b/src/createWorker.js
index 344d6b8..1459351 100644
--- a/src/createWorker.js
+++ b/src/createWorker.js
@@ -106,33 +106,35 @@ module.exports = (_options = {}) => {
     }))
   );
 
-  const transcode = (inputPath, outputPath, opts = '', del = true, jobId) => (
+  const transcode = (input, output, opts = '', del = true, jobId) => (
     run(
-      `${opts} -i /data/${inputPath} ${outputPath}`,
-      { inputPath, outputPath, del },
+      `${opts} -i /data/${input} ${output}`,
+      { input, output, del },
       jobId,
     )
   );
 
-  const trim = (inputPath, outputPath, from, to, opts = '', del = true, jobId) => (
+  const trim = (input, output, from, to, opts = '', del = true, jobId) => (
     run(
-      `${opts} -i /data/${inputPath} -ss ${from} -to ${to} -c copy ${outputPath}`,
-      { inputPath, outputPath, del },
+      `${opts} -i /data/${input} -ss ${from} -to ${to} -c copy ${output}`,
+      { input, output, del },
       jobId,
     )
   );
 
-  const concatDemuxer = async (inputPaths, outputPath, opts = '', del = true, jobId) => {
-    const text = inputPaths.reduce((acc, input) => `${acc}\nfile ${input}`, '');
+  const concatDemuxer = async (input, output, opts = '', del = true, jobId) => {
+    const text = input.reduce((acc, path) => `${acc}\nfile ${path}`, '');
     await writeText('concat_list.txt', text);
-    return run(`${opts} -f concat -safe 0 -i /data/concat_list.txt -c copy ${outputPath}`,
-      { del, outputPath, inputPaths: [...inputPaths, 'concat_list.txt'] },
+    return run(`${opts} -f concat -safe 0 -i /data/concat_list.txt -c copy ${output}`,
+      { del, output, input: [...input, 'concat_list.txt'] },
       jobId);
   };
 
   const ls = (path, jobId) => (
     startJob(createJob({
-      id: jobId, action: 'ls', payload: { path },
+      id: jobId,
+      action: 'FS',
+      payload: { method: 'readdir', args: [path] },
     }))
   );
 
@@ -154,10 +156,13 @@ module.exports = (_options = {}) => {
     if (status === 'resolve') {
       log(`[${workerId}]: Complete ${jobId}`);
       let d = data;
-      if (action === 'read') {
-        d = Uint8Array.from({ ...data, length: Object.keys(data).length });
-      } else {
-        logger(d);
+      if (action === 'FS') {
+        const { method, data: _data } = data;
+        if (method === 'readFile') {
+          d = Uint8Array.from({ ..._data, length: Object.keys(_data).length });
+        } else {
+          d = _data;
+        }
       }
       resolves[action]({ jobId, data: d });
     } else if (status === 'reject') {
diff --git a/src/worker-script/index.js b/src/worker-script/index.js
index ae90ab8..269a8e7 100644
--- a/src/worker-script/index.js
+++ b/src/worker-script/index.js
@@ -1,31 +1,12 @@
 require('regenerator-runtime/runtime');
 const defaultArgs = require('./constants/defaultArgs');
+const strList2ptr = require('./utils/strList2ptr');
 
 let action = 'unknown';
 let Module = null;
 let adapter = null;
 let ffmpeg = null;
 
-const str2ptr = (s) => {
-  const ptr = Module._malloc((s.length + 1) * Uint8Array.BYTES_PER_ELEMENT);
-  for (let i = 0; i < s.length; i += 1) {
-    Module.setValue(ptr + i, s.charCodeAt(i), 'i8');
-  }
-  Module.setValue(ptr + s.length, 0, 'i8');
-  return ptr;
-};
-
-const strList2ptr = (strList) => {
-  const listPtr = Module._malloc(strList.length * Uint32Array.BYTES_PER_ELEMENT);
-
-  strList.forEach((s, idx) => {
-    const strPtr = str2ptr(s);
-    Module.setValue(listPtr + (4 * idx), strPtr, 'i32');
-  });
-
-  return listPtr;
-};
-
 const load = ({ workerId, payload: { options: { corePath } } }, res) => {
   if (Module == null) {
     const Core = adapter.getCore(corePath);
@@ -54,33 +35,57 @@ const syncfs = async ({
   res.resolve({ message: `Sync file system with populate=${populate}` });
 };
 
-const ls = ({
+const FS = ({
   payload: {
-    path,
+    method,
+    args,
   },
 }, res) => {
-  const dirs = Module.FS.readdir(path);
-  res.resolve({ message: `List path ${path}`, dirs });
+  const data = Module.FS[method](...args);
+  res.resolve({
+    message: `${method} ${args.join(',')}`,
+    method,
+    data,
+  });
 };
 
 const run = async ({
   payload: {
     args: _args,
     options: {
-      inputPath, inputPaths, outputPath, del,
+      input, output, del = true,
     },
   },
 }, res) => {
   const args = [...defaultArgs, ..._args.trim().split(' ')];
-  ffmpeg(args.length, strList2ptr(args));
-  await adapter.fs.writeFile(outputPath, Module.FS.readFile(outputPath));
-  Module.FS.unlink(outputPath);
-  if (del && typeof inputPath === 'string') {
-    await adapter.fs.deleteFile(inputPath);
-  } else if (del && Array.isArray(inputPaths)) {
-    inputPaths.reduce((promise, input) => promise.then(() => adapter.fs.deleteFile(input)),
-      Promise.resolve());
+  ffmpeg(args.length, strList2ptr(Module, args));
+
+  /*
+   * After executing the ffmpeg command, the data is saved in MEMFS,
+   * if `output` is specified in the options, here ffmpeg.js will move
+   * these files to IDBFS or NODEFS here.
+   */
+  if (typeof output === 'string') {
+    await adapter.fs.writeFile(output, Module.FS.readFile(output));
+    Module.FS.unlink(output);
+  } else if (Array.isArray(output)) {
+    await Promise.all(output.map(async (p) => {
+      await adapter.fs.writeFile(p, Module.FS.readFile(p));
+      Module.FS.unlink(p);
+    }));
   }
+
+  /*
+   * To prevent input files occupy filesystem without notice,
+   * if `input` is specified in the options, ffmpeg.js cleans these
+   * files for you
+   */
+  if (del && typeof input === 'string') {
+    await adapter.fs.deleteFile(input);
+  } else if (del && Array.isArray(input)) {
+    await Promise.all(input.map((p) => adapter.fs.deleteFile(p)));
+  }
+
   res.resolve({ message: `Complete ${args.join(' ')}` });
 };
 
@@ -100,8 +105,8 @@ exports.dispatchHandlers = (packet, send) => {
   try {
     ({
       load,
-      ls,
       syncfs,
+      FS,
       run,
     })[packet.action](packet, res);
   } catch (err) {
diff --git a/src/worker-script/utils/str2ptr.js b/src/worker-script/utils/str2ptr.js
new file mode 100644
index 0000000..f8e1198
--- /dev/null
+++ b/src/worker-script/utils/str2ptr.js
@@ -0,0 +1,8 @@
+module.exports = (Module, s) => {
+  const ptr = Module._malloc((s.length + 1) * Uint8Array.BYTES_PER_ELEMENT);
+  for (let i = 0; i < s.length; i += 1) {
+    Module.setValue(ptr + i, s.charCodeAt(i), 'i8');
+  }
+  Module.setValue(ptr + s.length, 0, 'i8');
+  return ptr;
+};
diff --git a/src/worker-script/utils/strList2ptr.js b/src/worker-script/utils/strList2ptr.js
new file mode 100644
index 0000000..a3af49f
--- /dev/null
+++ b/src/worker-script/utils/strList2ptr.js
@@ -0,0 +1,12 @@
+const str2ptr = require('./str2ptr');
+
+module.exports = (Module, strList) => {
+  const listPtr = Module._malloc(strList.length * Uint32Array.BYTES_PER_ELEMENT);
+
+  strList.forEach((s, idx) => {
+    const strPtr = str2ptr(Module, s);
+    Module.setValue(listPtr + (4 * idx), strPtr, 'i32');
+  });
+
+  return listPtr;
+};