3.8. The Debugger

The Erlang debugger is a graphical tool providing mechanisms to debug sequential code and influence program execution. It allows the user to step through programs while inspecting and manipulating variables. You can set breakpoints that stop the execution as well as inspect the recursive stack and variable bindings at each level. This section should serve as only a brief introduction to the debugger, and should be enough to get you started in using it. There are many features and details we have not covered, all of which are documented in the Debugger User’s Guide, available in the online documentation.

You start the debugger by typing debugger:start() and a monitor window appears. This window displays a list of trace-compiled modules, attached (traced) processes, and other debug-related settings (see Figure 3-2).