No, a node is not a file—it's a running process (an active program) in the ROS system. However, the code for a node is typically defined in a single Python/C++ file (or multiple files for complex nodes). Here's the distinction:

Key Clarification

1. Node Code
   • Written in a file (e.g., my_node.py or my_node.cpp)
   • Defines the node's behavior (publishers, subscribers, services, etc.)
2. Node Process
   • The running instance of that code (e.g., when you execute ros2 run my_package my_node.py)
   • Becomes a participant in the ROS network once launched

Example Workflow

1. Write code in draw_square.py (the file)

2. Run the code:

   bashros2 run my_package draw_square.py

3. Result: A node (process) named draw_square is now active in the ROS network

Why This Matters

• Modularity: You can have multiple nodes in a single package (e.g., one node for navigation, another for sensor processing).
• Reusability: The same node code can be launched multiple times with different parameters (e.g., controlling different robots).
• Independence: Nodes can crash/restart independently without affecting others (e.g., a sensor driver node can fail while the navigation node keeps running).

File vs. Node

In short:

A node is not a file—it’s the execution of that file as a process. The file contains the instructions, but the node is the active program doing the work.

Answer from Perplexity: pplx.ai/share