Filesystem MCP Server

import fs from 'fs/promises'; import { normalizeLineEndings } from './utils.js'; export async function tailFile(filePath: string, numLines: number): Promise<string> { const CHUNK_SIZE = 1024; const stats = await fs.stat(filePath); const fileSize = stats.size; if (fileSize === 0) return ''; const fileHandle = await fs.open(filePath, 'r'); try { const lines: string[] = []; let position = fileSize; let chunk = Buffer.alloc(CHUNK_SIZE); let linesFound = 0; let remainingText = ''; while (position > 0 && linesFound < numLines) { const size = Math.min(CHUNK_SIZE, position); position -= size; const { bytesRead } = await fileHandle.read(chunk, 0, size, position); if (!bytesRead) break; const readData = chunk.slice(0, bytesRead).toString('utf-8'); const chunkText = readData + remainingText; const chunkLines = normalizeLineEndings(chunkText).split('\n'); if (position > 0) { remainingText = chunkLines[0]; chunkLines.shift(); } for (let i = chunkLines.length - 1; i >= 0 && linesFound < numLines; i--) { lines.unshift(chunkLines[i]); linesFound++; } } return lines.join('\n'); } finally { await fileHandle.close(); } } export async function headFile(filePath: string, numLines: number): Promise<string> { const fileHandle = await fs.open(filePath, 'r'); try { const lines: string[] = []; let buffer = ''; let bytesRead = 0; const chunk = Buffer.alloc(1024); while (lines.length < numLines) { const result = await fileHandle.read(chunk, 0, chunk.length, bytesRead); if (result.bytesRead === 0) break; bytesRead += result.bytesRead; buffer += chunk.slice(0, result.bytesRead).toString('utf-8'); const newLineIndex = buffer.lastIndexOf('\n'); if (newLineIndex !== -1) { const completeLines = buffer.slice(0, newLineIndex).split('\n'); buffer = buffer.slice(newLineIndex + 1); for (const line of completeLines) { lines.push(line); if (lines.length >= numLines) break; } } } if (buffer.length > 0 && lines.length < numLines) lines.push(buffer); return lines.join('\n'); } finally { await fileHandle.close(); } }