platform-pattern-2-filesystem-operations

description: Use FileSystem module for safe, resource-managed file operations with proper error handling and cleanup. globs: "**/*.ts" alwaysApply: true

Platform Pattern 2: Filesystem Operations

Rule: Use FileSystem module for safe, resource-managed file operations with proper error handling and cleanup.

Example

This example demonstrates reading, writing, and manipulating files.

import { FileSystem, Effect, Stream } from "@effect/platform";
import * as fs from "fs/promises";

const program = Effect.gen(function* () {
  console.log(`\n[FILESYSTEM] Demonstrating file operations\n`);

  // Example 1: Write a file
  console.log(`[1] Writing file:\n`);

  const content = `Hello, Effect-TS!\nThis is a test file.\nCreated at ${new Date().toISOString()}`;

  yield* FileSystem.writeFileUtf8("test.txt", content);

  yield* Effect.log(`✓ File written: test.txt`);

  // Example 2: Read the file
  console.log(`\n[2] Reading file:\n`);

  const readContent = yield* FileSystem.readFileUtf8("test.txt");

  console.log(readContent);

  // Example 3: Get file stats
  console.log(`\n[3] File stats:\n`);

  const stats = yield* FileSystem.stat("test.txt").pipe(
    Effect.flatMap((stat) =>
      Effect.succeed({
        size: stat.size,
        isFile: stat.isFile(),
        modified: stat.mtimeMs,
      })
    )
  );

  console.log(`  Size: ${stats.size} bytes`);
  console.log(`  Is file: ${stats.isFile}`);
  console.log(`  Modified: ${new Date(stats.modified).toISOString()}`);

  // Example 4: Create directory and write multiple files
  console.log(`\n[4] Creating directory and files:\n`);

  yield* FileSystem.mkdir("test-dir");

  yield* Effect.all(
    Array.from({ length: 3 }, (_, i) =>
      FileSystem.writeFileUtf8(
        `test-dir/file-${i + 1}.txt`,
        `Content of file ${i + 1}`
      )
    )
  );

  yield* Effect.log(`✓ Created directory with 3 files`);

  // Example 5: List directory contents
  console.log(`\n[5] Listing directory:\n`);

  const entries = yield* FileSystem.readDirectory("test-dir");

  entries.forEach((entry) => {
    console.log(`  - ${entry}`);
  });

  // Example 6: Append to file
  console.log(`\n[6] Appending to file:\n`);

  const appendContent = `\nAppended line at ${new Date().toISOString()}`;

  yield* FileSystem.appendFileUtf8("test.txt", appendContent);

  const finalContent = yield* FileSystem.readFileUtf8("test.txt");

  console.log(`File now has ${finalContent.split("\n").length} lines`);

  // Example 7: Clean up
  console.log(`\n[7] Cleaning up:\n`);

  yield* Effect.all(
    Array.from({ length: 3 }, (_, i) =>
      FileSystem.remove(`test-dir/file-${i + 1}.txt`)
    )
  );

  yield* FileSystem.remove("test-dir");
  yield* FileSystem.remove("test.txt");

  yield* Effect.log(`✓ Cleanup complete`);
});

Effect.runPromise(program);