mcp-ssh-tool

Instructions

Implementation Reference

• src/fs-tools.ts:40-89 (handler)

  The handler function that performs the file write operation, using an atomic write approach (temp file then rename).

  export async function writeFile(
    sessionId: string,
    path: string,
    data: string,
    mode?: number
  ): Promise<boolean> {
    logger.debug('Writing file', { sessionId, path, size: data.length, mode });
    
    const session = sessionManager.getSession(sessionId);
    if (!session) {
      throw new Error(`Session ${sessionId} not found or expired`);
    }
    
    try {
      // Use atomic write: write to temp file, then rename
      const tempPath = `${path}.tmp.${Date.now()}`;
      
      try {
        // Write to temporary file
        await session.sftp.put(Buffer.from(data, 'utf8'), tempPath);
        
        // Set permissions if specified
        if (mode !== undefined) {
          await session.sftp.chmod(tempPath, mode);
        }
        
        // Atomic rename
        await session.sftp.rename(tempPath, path);
        
        logger.debug('File written successfully', { sessionId, path });
        return true;
      } catch (writeError) {
        // Clean up temp file on failure
        try {
          await session.sftp.delete(tempPath);
          logger.debug('Cleaned up temp file after error', { tempPath });
        } catch (cleanupError) {
          logger.warn('Failed to clean up temp file', { tempPath, cleanupError });
        }
        throw writeError;
      }
    } catch (error) {
      logger.error('Failed to write file', { sessionId, path, error });
      throw wrapError(
        error,
        ErrorCode.EFS,
        `Failed to write file ${path}. Check directory permissions and disk space.`
      );
    }
  }

• src/types.ts:251-256 (schema)

  The Zod schema used to validate inputs for the 'fs_write' tool.

  export const FSWriteSchema = z.object({
    sessionId: z.string().min(1),
    path: z.string().min(1),
    data: z.string(),
    mode: z.number().optional()
  });

• src/mcp.ts:433-438 (registration)

  The tool handler case that processes 'fs_write' requests and calls the implementation.

  case 'fs_write': {
    const params = FSWriteSchema.parse(args);
    const result = await writeFile(params.sessionId, params.path, params.data, params.mode);
    logger.info('File written', { sessionId: params.sessionId, path: params.path });
    return { content: [{ type: 'text', text: JSON.stringify(result, null, 2) }] };
  }