Modding:Starbound Log File
The Starbound log file is a text file where the game engine writes a lot of debugging and status information, along with errors. Lua scripts can also write to it by using sb.logInfo() and similar utility functions. This file can get quite large, and is rotated everytime the game restart. This means "starbound.log" becomes "starbound.log.0", "starbound.log.0" becomes "starbound.log.1" and so on.
You can find your log files at this path:
Or for steam:
If you run a server, there is a log file specifically for it:
Monitoring the file in real-time
For debug purposes, it can be interesting to see what gets written to this file in real-time. There are tools you can use to monitor it as it update in (almost) realtime. On Linux & MacOS, the most common would be, from a console:
tail -f starbound.log
For Windows, there are several tail-like options with graphical interface such as mTail. If you prefer the *nix-like tools, you can use Cygwin and, on the latest versions of Windows, the Windows Subsystem for Linux; for more informations, refer to your favorite search engine.