MCP SmallEdit

Instructions

Implementation Reference

• src/index.ts:567-606 (handler)

  The handler for the 'sed_edit' tool. Parses arguments, checks file existence, constructs and executes a Perl command using the provided sed-like pattern for editing the file. Supports preview mode (with diff) and backup creation. Returns success message or preview output.
  case 'sed_edit': { const { file, pattern, backup = true, preview = false } = args; // Check if file exists if (!existsSync(file)) { throw new Error(`File not found: ${file}`); } // Build sed command - use perl for better compatibility let sedCmd; if (preview) { // For preview, create a temp copy and diff const tempFile = `${file}.preview.tmp`; await execAsync(`rm -f .bak; cp '${file}' '${tempFile}'`); // Apply change to temp file sedCmd = `perl -i -pe '${pattern}' '${tempFile}' && diff -u '${file}' '${tempFile}' | head -50; rm -f '${tempFile}'`; } else { // Use perl for actual edits (more portable than sed) const backupExt = backup ? '.bak' : ''; sedCmd = `perl -i${backupExt} -pe '${pattern}' '${file}'`; } const { stdout, stderr } = await execAsync(sedCmd); if (stderr) { throw new Error(`Sed error: ${stderr}`); } return { content: [ { type: 'text', text: preview ? `Preview of changes:\n${stdout || 'No changes would be made'}` : `Successfully edited ${file}${backup ? ' (backup created as .bak)' : ''}` } ] }; }
• src/index.ts:39-66 (schema)

  The input schema definition for the sed_edit tool, defining parameters: file (required string), pattern (required string), backup (optional boolean, default true), preview (optional boolean, default false).
  { name: 'sed_edit', description: 'Make small edits to files using sed patterns. Efficient for single-line changes, pattern replacements, and simple text transformations.', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'Path to the file to edit' }, pattern: { type: 'string', description: 'Sed pattern (e.g., "s/old/new/g" for substitution)' }, backup: { type: 'boolean', default: true, description: 'Create backup file before editing' }, preview: { type: 'boolean', default: false, description: 'Preview changes without modifying file' } }, required: ['file', 'pattern'] } },
• src/index.ts:36-280 (registration)

  The registration of all tools including sed_edit via the ListToolsRequestSchema handler, which returns the list of available tools with their schemas.
  server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: [ { name: 'sed_edit', description: 'Make small edits to files using sed patterns. Efficient for single-line changes, pattern replacements, and simple text transformations.', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'Path to the file to edit' }, pattern: { type: 'string', description: 'Sed pattern (e.g., "s/old/new/g" for substitution)' }, backup: { type: 'boolean', default: true, description: 'Create backup file before editing' }, preview: { type: 'boolean', default: false, description: 'Preview changes without modifying file' } }, required: ['file', 'pattern'] } }, { name: 'sed_multifile', description: 'Apply sed pattern to multiple files matching a glob pattern', inputSchema: { type: 'object', properties: { pattern: { type: 'string', description: 'Sed pattern to apply' }, filePattern: { type: 'string', description: 'File glob pattern (e.g., "*.ts", "src/**/*.js")' }, directory: { type: 'string', default: '.', description: 'Starting directory for search' }, backup: { type: 'boolean', default: true, description: 'Create backup files' } }, required: ['pattern', 'filePattern'] } }, { name: 'awk_process', description: 'Process files using AWK for more complex operations like column manipulation, calculations, or conditional processing', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'Input file path' }, script: { type: 'string', description: 'AWK script to execute' }, outputFile: { type: 'string', description: 'Output file path (optional, defaults to stdout)' } }, required: ['file', 'script'] } }, { name: 'quick_replace', description: 'Simple find and replace across a file without regex', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to edit' }, find: { type: 'string', description: 'Text to find (literal, not regex)' }, replace: { type: 'string', description: 'Text to replace with' }, all: { type: 'boolean', default: true, description: 'Replace all occurrences (false = first only)' } }, required: ['file', 'find', 'replace'] } }, { name: 'line_edit', description: 'Edit specific lines by number or range', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to edit' }, lineNumber: { type: 'number', description: 'Line number to edit (1-based)' }, lineRange: { type: 'string', description: 'Line range (e.g., "10,20" or "5,$")' }, action: { type: 'string', enum: ['replace', 'delete', 'insert_after', 'insert_before'], description: 'Action to perform' }, content: { type: 'string', description: 'New content (for replace/insert actions)' } }, required: ['file', 'action'] } }, { name: 'perl_edit', description: 'Edit files using Perl one-liners (more powerful than sed, better cross-platform support)', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to edit' }, script: { type: 'string', description: 'Perl script (e.g., "s/old/new/g" or "$_ = uc" for uppercase)' }, backup: { type: 'boolean', default: true, description: 'Create backup file' }, multiline: { type: 'boolean', default: false, description: 'Enable multiline mode (-0777)' } }, required: ['file', 'script'] } }, { name: 'diff_preview', description: 'Preview what changes would be made by showing a diff', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to preview changes for' }, command: { type: 'string', description: 'Command that would make changes (e.g., "s/old/new/g")' }, tool: { type: 'string', enum: ['sed', 'perl', 'awk'], default: 'perl', description: 'Which tool to use for the preview' } }, required: ['file', 'command'] } }, { name: 'restore_backup', description: 'Restore a file from its most recent backup (.bak)', inputSchema: { type: 'object', properties: { file: { type: 'string', description: 'File to restore from backup' }, keepBackup: { type: 'boolean', default: true, description: 'Keep the backup file after restoring' } }, required: ['file'] } }, { name: 'list_backups', description: 'List all backup files in a directory', inputSchema: { type: 'object', properties: { directory: { type: 'string', default: '.', description: 'Directory to search for backup files' }, pattern: { type: 'string', default: '*.bak', description: 'Backup file pattern' } } } }, { name: 'help', description: 'Get detailed help and examples for smalledit tools', inputSchema: { type: 'object', properties: { tool: { type: 'string', description: 'Tool name for help (e.g., "sed_edit", "perl_edit") or "all" for overview' } } } } ] }; });
• src/index.ts:358-382 (helper)

  Help content and examples for the sed_edit tool, stored in helpContent object.
  sed_edit: `sed_edit - Pattern-based file editing =================================== Uses perl backend for cross-platform compatibility. Examples: // Simple replacement sed_edit({ file: "config.json", pattern: "s/localhost/production/g" }) // Delete lines containing pattern sed_edit({ file: "app.js", pattern: "$_ = '' if /console\\.log/" }) // Preview changes first sed_edit({ file: "test.txt", pattern: "s/old/new/g", preview: true }) // Edit without backup sed_edit({ file: "temp.txt", pattern: "s/a/b/g", backup: false }) Note: Actually uses perl internally for better compatibility. WHEN NOT TO USE: - Multi-line replacements - Complex code modifications - JSON/YAML structure changes → Use filesystem:edit_file instead! `,