diff --git a/src/bin/create-index.js b/src/bin/create-index.js
new file mode 100644
index 0000000..9f2adc3
--- /dev/null
+++ b/src/bin/create-index.js
@@ -0,0 +1,16 @@
+#!/usr/bin/env node
+
+import yargs from 'yargs';
+import writeIndex from './../writeIndex';
+
+let argv;
+
+argv = yargs
+    .demand(1)
+    .argv;
+
+writeIndex(argv._);
+
+/* eslint-disable no-console */
+console.log('OK!');
+/* eslint-enable no-console */
diff --git a/src/createIndexCode.js b/src/createIndexCode.js
new file mode 100644
index 0000000..73812f1
--- /dev/null
+++ b/src/createIndexCode.js
@@ -0,0 +1,56 @@
+import _ from 'lodash';
+
+let buildExportBlock,
+    buildImportBlock,
+    safeVariableName;
+
+safeVariableName = (fileName) => {
+    let indexOfDot;
+
+    indexOfDot = fileName.indexOf('.');
+
+    if (indexOfDot === -1) {
+        return fileName;
+    } else {
+        return fileName.slice(0, indexOfDot);
+    }
+};
+
+buildImportBlock = (files) => {
+    let importBlock;
+
+    importBlock = _.map(files, (fileName) => {
+        return 'import ' + safeVariableName(fileName) + ' from \'./' + fileName + '\';';
+    });
+
+    importBlock = importBlock.join('\n');
+
+    return importBlock;
+};
+
+buildExportBlock = (files) => {
+    let exportBlock;
+
+    exportBlock = _.map(files, (fileName) => {
+        return '    ' + safeVariableName(fileName);
+    });
+
+    exportBlock = 'export {\n' + exportBlock.join(',\n') + '\n};';
+
+    return exportBlock;
+};
+
+export default (filePaths) => {
+    let code,
+        sortedFilePaths;
+
+    code = '\'create index\';\n\n';
+
+    if (filePaths.length) {
+        sortedFilePaths = filePaths.sort();
+
+        code += buildImportBlock(sortedFilePaths) + '\n\n' + buildExportBlock(sortedFilePaths) + '\n\n';
+    }
+
+    return code;
+};
diff --git a/src/readDirectory.js b/src/readDirectory.js
new file mode 100644
index 0000000..4d020ab
--- /dev/null
+++ b/src/readDirectory.js
@@ -0,0 +1,97 @@
+import fs from 'fs';
+import _ from 'lodash';
+import path from 'path';
+import validateTargetDirectory from './validateTargetDirectory';
+
+let hasIndex,
+    hasMultipleExtensions,
+    hasNoExtension,
+    isSafeName,
+    removeDuplicates;
+
+hasIndex = (directoryPath) => {
+    let indexPath;
+
+    indexPath = path.resolve(directoryPath, 'index.js');
+
+    try {
+        fs.statSync(indexPath);
+
+        return true;
+    } catch (error) {
+        return false;
+    }
+};
+
+hasNoExtension = (fileName) => {
+    let matches;
+
+    matches = fileName.match(/\./g);
+
+    return !matches;
+};
+
+hasMultipleExtensions = (fileName) => {
+    let matches;
+
+    matches = fileName.match(/\./g);
+
+    return matches && matches.length > 1;
+};
+
+isSafeName = (fileName) => {
+    return /^[a-z][a-z0-9\.]+$/i.test(fileName);
+};
+
+removeDuplicates = (files) => {
+    return _.filter(files, (fileName) => {
+        return !_.includes(files, fileName + '.js');
+    });
+};
+
+export default (directoryPath) => {
+    let children;
+
+    validateTargetDirectory(directoryPath);
+
+    children = fs.readdirSync(directoryPath);
+
+    children = _.filter(children, (fileName) => {
+        let absolutePath,
+            isDirectory;
+
+        absolutePath = path.resolve(directoryPath, fileName);
+
+        isDirectory = fs.statSync(absolutePath).isDirectory();
+
+        if (!isSafeName(fileName)) {
+            return false;
+        }
+
+        if (hasNoExtension(fileName) && !isDirectory) {
+            return false;
+        }
+
+        if (hasMultipleExtensions(fileName)) {
+            return false;
+        }
+
+        if (_.startsWith(fileName, 'index.js')) {
+            return false;
+        }
+
+        if (!isDirectory && !_.endsWith(fileName, '.js')) {
+            return false;
+        }
+
+        if (isDirectory && !hasIndex(absolutePath)) {
+            return false;
+        }
+
+        return true;
+    });
+
+    children = removeDuplicates(children);
+
+    return children.sort();
+};
diff --git a/src/sortByDepth.js b/src/sortByDepth.js
new file mode 100644
index 0000000..dc7b36e
--- /dev/null
+++ b/src/sortByDepth.js
@@ -0,0 +1,7 @@
+import _ from 'lodash';
+
+export default (paths) => {
+    return _.sortBy(paths, (path) => {
+        return -path.split('/').length;
+    });
+};
diff --git a/src/validateTargetDirectory.js b/src/validateTargetDirectory.js
new file mode 100644
index 0000000..abf0638
--- /dev/null
+++ b/src/validateTargetDirectory.js
@@ -0,0 +1,35 @@
+import _ from 'lodash';
+import fs from 'fs';
+import path from 'path';
+
+export default (targetDirectory) => {
+    let indexFile,
+        indexFilePath,
+        stats;
+
+    try {
+        stats = fs.statSync(targetDirectory);
+    } catch (error) {
+        throw new Error('Directory "' + targetDirectory + '" does not exist.');
+    }
+
+    if (!stats.isDirectory()) {
+        throw new Error('"' + targetDirectory + '" is not a directory.');
+    }
+
+    indexFilePath = path.resolve(targetDirectory, './index.js');
+
+    try {
+        fs.statSync(indexFilePath);
+    } catch (error) {
+        return true;
+    }
+
+    indexFile = fs.readFileSync(indexFilePath, 'utf8');
+
+    if (!_.startsWith(indexFile, '\'create index\';\n')) {
+        throw new Error('"' + indexFilePath + '" unsafe index.');
+    }
+
+    return true;
+};
diff --git a/src/writeIndex.js b/src/writeIndex.js
new file mode 100644
index 0000000..bbb521c
--- /dev/null
+++ b/src/writeIndex.js
@@ -0,0 +1,31 @@
+import _ from 'lodash';
+import createIndexCode from './createIndexCode';
+import fs from 'fs';
+import path from 'path';
+import validateTargetDirectory from './validateTargetDirectory';
+import readDirectory from './readDirectory';
+import sortByDepth from './sortByDepth';
+
+export default (directoryPaths) => {
+    let sortedDirectoryPaths;
+
+    sortedDirectoryPaths = sortByDepth(directoryPaths);
+
+    _.forEach(sortedDirectoryPaths, (directoryPath) => {
+        validateTargetDirectory(directoryPath);
+    });
+
+    _.forEach(sortedDirectoryPaths, (directoryPath) => {
+        let indexCode,
+            indexFilePath,
+            siblings;
+
+        siblings = readDirectory(directoryPath);
+
+        indexCode = createIndexCode(siblings);
+
+        indexFilePath = path.resolve(directoryPath, 'index.js');
+
+        fs.writeFileSync(indexFilePath, indexCode);
+    });
+};
diff --git a/tests/codeExample.js b/tests/codeExample.js
new file mode 100644
index 0000000..c11c5aa
--- /dev/null
+++ b/tests/codeExample.js
@@ -0,0 +1,5 @@
+import _ from 'lodash';
+
+export default (code) => {
+    return _.trim(code) + '\n\n';
+};
diff --git a/tests/createIndexCode.js b/tests/createIndexCode.js
new file mode 100644
index 0000000..2e67e4b
--- /dev/null
+++ b/tests/createIndexCode.js
@@ -0,0 +1,89 @@
+/* eslint-disable no-restricted-syntax */
+
+import {
+    expect
+} from 'chai';
+
+import createIndexCode from './../src/createIndexCode';
+
+import codeExample from './codeExample';
+
+describe('createIndexCode()', () => {
+    it('describes no children', () => {
+        let indexCode;
+
+        indexCode = createIndexCode([]);
+
+        expect(indexCode).to.equal(codeExample(`
+'create index';
+        `));
+    });
+    it('describes a single child', () => {
+        let indexCode;
+
+        indexCode = createIndexCode(['foo']);
+
+        expect(indexCode).to.equal(codeExample(`
+'create index';
+
+import foo from './foo';
+
+export {
+    foo
+};
+        `));
+    });
+    it('describes multiple children', () => {
+        let indexCode;
+
+        indexCode = createIndexCode(['bar', 'foo']);
+
+        expect(indexCode).to.equal(codeExample(`
+'create index';
+
+import bar from './bar';
+import foo from './foo';
+
+export {
+    bar,
+    foo
+};
+        `));
+    });
+    context('file with extension', () => {
+        it('removes the extension from the export statement', () => {
+            let indexCode;
+
+            indexCode = createIndexCode(['foo.js']);
+
+            expect(indexCode).to.equal(codeExample(`
+'create index';
+
+import foo from './foo.js';
+
+export {
+    foo
+};
+            `));
+        });
+    });
+    context('multiple, unsorted', () => {
+        it('sorts the files', () => {
+            let indexCode;
+
+            indexCode = createIndexCode(['foo', 'bar']);
+
+            expect(indexCode).to.equal(codeExample(`
+'create index';
+
+import bar from './bar';
+import foo from './foo';
+
+export {
+    bar,
+    foo
+};
+            `));
+        });
+    });
+});
diff --git a/tests/fixtures/read-directory/children-directories-and-files/foo.js b/tests/fixtures/read-directory/children-directories-and-files/foo.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-directories-and-files/foo/index.js b/tests/fixtures/read-directory/children-directories-and-files/foo/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-and-files/foo/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-and-files/present.js b/tests/fixtures/read-directory/children-directories-and-files/present.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-directories-unsafe-name/bar-bar/index.js b/tests/fixtures/read-directory/children-directories-unsafe-name/bar-bar/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-unsafe-name/bar-bar/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-unsafe-name/foo-foo/index.js b/tests/fixtures/read-directory/children-directories-unsafe-name/foo-foo/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-unsafe-name/foo-foo/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-unsafe-name/present/index.js b/tests/fixtures/read-directory/children-directories-unsafe-name/present/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-unsafe-name/present/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-without-index/bar/bar.js b/tests/fixtures/read-directory/children-directories-without-index/bar/bar.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-without-index/bar/bar.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-without-index/foo/foo.js b/tests/fixtures/read-directory/children-directories-without-index/foo/foo.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-without-index/foo/foo.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories-without-index/present.js b/tests/fixtures/read-directory/children-directories-without-index/present.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories-without-index/present.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories/bar/index.js b/tests/fixtures/read-directory/children-directories/bar/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories/bar/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-directories/foo/index.js b/tests/fixtures/read-directory/children-directories/foo/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-directories/foo/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-dot-files/present.js b/tests/fixtures/read-directory/children-dot-files/present.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-multiple-extensions/bar.bar.js b/tests/fixtures/read-directory/children-files-multiple-extensions/bar.bar.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-multiple-extensions/foo.foo.js b/tests/fixtures/read-directory/children-files-multiple-extensions/foo.foo.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-multiple-extensions/present.js b/tests/fixtures/read-directory/children-files-multiple-extensions/present.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-no-extension/bar b/tests/fixtures/read-directory/children-files-no-extension/bar
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-no-extension/foo b/tests/fixtures/read-directory/children-files-no-extension/foo
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files-no-extension/present.js b/tests/fixtures/read-directory/children-files-no-extension/present.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files/bar.js b/tests/fixtures/read-directory/children-files/bar.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-files/foo.js b/tests/fixtures/read-directory/children-files/foo.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/read-directory/children-index/bar/index.js b/tests/fixtures/read-directory/children-index/bar/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-index/bar/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-index/foo/index.js b/tests/fixtures/read-directory/children-index/foo/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-index/foo/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/read-directory/children-index/index.js b/tests/fixtures/read-directory/children-index/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/read-directory/children-index/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/validate-target-directory/no-index/present.js b/tests/fixtures/validate-target-directory/no-index/present.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/validate-target-directory/not-a-directory.js b/tests/fixtures/validate-target-directory/not-a-directory.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/validate-target-directory/safe-index/index.js b/tests/fixtures/validate-target-directory/safe-index/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/validate-target-directory/safe-index/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/validate-target-directory/unsafe-index/index.js b/tests/fixtures/validate-target-directory/unsafe-index/index.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/write-index/mixed/bar/index.js b/tests/fixtures/write-index/mixed/bar/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/write-index/mixed/bar/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/fixtures/write-index/mixed/foo.js b/tests/fixtures/write-index/mixed/foo.js
new file mode 100644
index 0000000..e69de29
diff --git a/tests/fixtures/write-index/mixed/foo/index.js b/tests/fixtures/write-index/mixed/foo/index.js
new file mode 100644
index 0000000..a45ca72
--- /dev/null
+++ b/tests/fixtures/write-index/mixed/foo/index.js
@@ -0,0 +1 @@
+'create index';
diff --git a/tests/readDirectory.js b/tests/readDirectory.js
new file mode 100644
index 0000000..0a87dba
--- /dev/null
+++ b/tests/readDirectory.js
@@ -0,0 +1,92 @@
+import {
+    expect
+} from 'chai';
+
+import path from 'path';
+import readDirectory from './../src/readDirectory';
+
+const fixturesPath = path.resolve(__dirname, './fixtures/read-directory');
+
+describe('readDirectory()', () => {
+    context('target directory contains child directories', () => {
+        it('gets names of the children directories', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-directories'));
+
+            expect(names).to.deep.equal(['bar', 'foo']);
+        });
+    });
+    context('target directory contains child directories that do not contain index', () => {
+        it('gets names of the children directories', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-directories-without-index'));
+
+            expect(names).to.deep.equal(['present.js']);
+        });
+    });
+    context('target directory contains child directories (unsafe name)', () => {
+        it('gets names of the children directories', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-directories-unsafe-name'));
+
+            expect(names).to.deep.equal(['present']);
+        });
+    });
+    context.skip('target directory contains ./index.js', () => {
+        it('does not include ./index.js', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-index'));
+
+            expect(names).to.deep.equal(['bar', 'foo']);
+        });
+    });
+    context('target directory contains files', () => {
+        it('refers to the files (with extension)', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-files'));
+
+            expect(names).to.deep.equal(['bar.js', 'foo.js']);
+        });
+    });
+    context('target directory contains dot files', () => {
+        it('ignores files', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-dot-files'));
+
+            expect(names).to.deep.equal(['present.js']);
+        });
+    });
+    context('target directory contains files with no extension', () => {
+        it('ignores files', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-files-no-extension'));
+
+            expect(names).to.deep.equal(['present.js']);
+        });
+    });
+    context('target directory contains files with multiple extensions', () => {
+        it('ignores files', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-files-multiple-extensions'));
+
+            expect(names).to.deep.equal(['present.js']);
+        });
+    });
+    context('target directory contains directories and files with the same name', () => {
+        it('prefers file', () => {
+            let names;
+
+            names = readDirectory(path.resolve(fixturesPath, 'children-directories-and-files'));
+
+            expect(names).to.deep.equal(['foo.js', 'present.js']);
+        });
+    });
+});
diff --git a/tests/sortByDepth.js b/tests/sortByDepth.js
new file mode 100644
index 0000000..60dfefc
--- /dev/null
+++ b/tests/sortByDepth.js
@@ -0,0 +1,22 @@
+import {
+    expect
+} from 'chai';
+import sortByDepth from './../src/sortByDepth';
+
+describe('sortByDepth()', () => {
+    it('sorts from deepest to the most shallow', () => {
+        let paths,
+            sortedPaths;
+
+        paths = [
+            '/b',
+            '/a',
+            '/a/b/c',
+            '/a/b'
+        ];
+
+        sortedPaths = sortByDepth(paths);
+
+        expect(sortedPaths).to.deep.equal(['/a/b/c', '/a/b', '/b', '/a']);
+    });
+});
diff --git a/tests/validateTargetDirectory.js b/tests/validateTargetDirectory.js
new file mode 100644
index 0000000..c8e7699
--- /dev/null
+++ b/tests/validateTargetDirectory.js
@@ -0,0 +1,47 @@
+/* eslint-disable max-nested-callbacks */
+
+import {
+    expect
+} from 'chai';
+import path from 'path';
+import validateTargetDirectory from './../src/validateTargetDirectory';
+
+const fixturesPath = path.resolve(__dirname, './fixtures/validate-target-directory');
+
+describe('validateTargetDirectory()', () => {
+    describe('directory path', () => {
+        context('refers to a directory that does not exist', () => {
+            it('throws an error', () => {
+                expect(() => {
+                    validateTargetDirectory(path.resolve(fixturesPath, 'does-not-exist'));
+                }).to.throw(Error, 'Directory "' + path.resolve(fixturesPath, 'does-not-exist') + '" does not exist.');
+            });
+        });
+        context('refers to a file', () => {
+            it('throws an error', () => {
+                expect(() => {
+                    validateTargetDirectory(path.resolve(fixturesPath, 'not-a-directory.js'));
+                }).to.throw(Error, '"' + path.resolve(fixturesPath, 'not-a-directory.js') + '" is not a directory.');
+            });
+        });
+    });
+    describe('target index', () => {
+        context('no index', () => {
+            it('returns true', () => {
+                expect(validateTargetDirectory(path.resolve(fixturesPath, 'no-index'))).to.equal(true);
+            });
+        });
+        context.skip('safe', () => {
+            it('returns true', () => {
+                expect(validateTargetDirectory(path.resolve(fixturesPath, 'safe-index'))).to.equal(true);
+            });
+        });
+        context('unsafe', () => {
+            it('throws an error', () => {
+                expect(() => {
+                    validateTargetDirectory(path.resolve(fixturesPath, 'unsafe-index'));
+                }).to.throw(Error, '"' + path.resolve(fixturesPath, 'unsafe-index/index.js') + '" unsafe index.');
+            });
+        });
+    });
+});
diff --git a/tests/writeIndex.js b/tests/writeIndex.js
new file mode 100644
index 0000000..2cfcfe6
--- /dev/null
+++ b/tests/writeIndex.js
@@ -0,0 +1,42 @@
+/* eslint-disable no-restricted-syntax */
+
+import {
+    expect
+} from 'chai';
+import fs from 'fs';
+import path from 'path';
+import codeExample from './codeExample';
+import writeIndex from './../src/writeIndex';
+
+const fixturesPath = path.resolve(__dirname, './fixtures/write-index');
+
+describe('writeIndex()', () => {
+    it('creates index in target directory', () => {
+        let indexCode,
+            indexFilePath;
+
+        indexFilePath = path.resolve(fixturesPath, './mixed/index.js');
+
+        try {
+            fs.unlinkSync(indexFilePath);
+        } catch (error) {
+
+        }
+
+        writeIndex([path.resolve(fixturesPath, './mixed')]);
+
+        indexCode = fs.readFileSync(indexFilePath, 'utf8');
+
+        expect(indexCode).to.equal(codeExample(`
+'create index';
+
+import bar from './bar';
+import foo from './foo.js';
+
+export {
+    bar,
+    foo
+};
+        `));
+    });
+});