How to debug matlab code without gui

Question

I have recently started using MATLAB without GUI by starting matlab with -nodesktop option and it is considerably faster.

However presently I have no way to debug a .m script in non gui mode. I have to open the default matlab editor every time I have to debug.Has anyone figured out a way to do it? Thanks in advance

I am using Ubuntu Linux, in case that helps.

Answer 1

To set breakpoints with the command line, dbstop is the tool (plus dbclear to clear breakpoints and dbstatus to list them).

There are presently 17 different forms to dbstop, which allow you to specify various combinations of:

1. The M-file in which to stop
2. Line number
3. Sub-function

4. Conditional to an arbitrary expression. For example,

   dbstop in myFun.m at 224 if ~exist('x','var')
   

5. At any run-time error (dbstop if error)
6. At a specific error (e.g dbstop if error myFun.m:barErrorId)
7. At any warning (dbstop if warning) or specific warning
8. If NaN or Inf are encountered (dbstop if naninf)

See the documentation for dbstop for details and good examples.

Also get used to dbcont (or F5), dbstep (or F10), dbquit (Shift+F5), dbstep (also dbstep in, dbstep out), dbstack (to see where you are and how you got there). The keyboard shortcuts may be different outside of Windows.

Far less used, but still very useful are dbup and dbdown, which allow you to switch workspace context (memory stacks).

See the summary of functions and a list of examples and how-to pages in the MathWorks page on Debugging.

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Related to the "db" functions is checkcode, which will check your code for possible problems before you even run it. This is a nice substitute for the red squiggly underlines that you would get in the MATLAB Editor.

Once you get a hang of dbstop and it's syntax, you won't often need to insert a keyboard into your code, but it's always an option.

Answer 2

Try placing the keyboard command in your code to insert a breakpoint. When the keyboard command is reached, MATLAB will drop into an interactive prompt that you can use to inspect variables. For example:

x = rand(10,10);
y = rand(10,5);
z = x * y;
keyboard; % you can interactively inspect x, y, z here
z = sort(z);

To leave keyboard mode, you can type dbquit to exit the program, or return to continue executing the program.

Another trick is to turn on dbstop if error which will automatically drop you into an interactive prompt whenever your code crashes.