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.
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:
The M-file in which to stop
Line number
Sub-function
Conditional to an arbitrary expression. For example,
dbstop in myFun.m at 224 if ~exist('x','var')
At any run-time error (dbstop if error)
At a specific error (e.g dbstop if error myFun.m:barErrorId)
At any warning (dbstop if warning) or specific warning
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.
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.
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.
You can use MATLAB -Dgdb if that helps. This sets gdb as the debugger. You will need to be familiar with gdb of course.
Once you do that, use the standard gdb commands to debug it.
EDIT
My mistake. Above won't work for M-Files. (Not having MATLAB to try things out is a pain :)
MATLAB has a pretty good set of debugging commands you can use from the commandline. If you insert keyboard commands in your MATLAB code, you can then use the commands.
You can use MATLAB's editor debug button to debug within MATLAB environment
Related
I need your help. I want debug a matlab code after specific iteration.
Suppose the following is the code:
**im=imread('C:\lena.tif');
[m n]=size(im);
for i=1:2:m-1
for j=1:2:n-1
enter into a function
..................
..................**
Suppose, when i = 505 and j = 460, the program will enter into the Debug Mode, and then I will debug the rest of the code using STEP IN (F11)
Please help me. Please please please......
Many thanks in advance.
Regards
- Jessy
As others have stated in the comments, you can use conditional breakpoints. It is important to point out that this can be done both interactively through the MATLAB editor or programmatically
dbstop in FUNCTION_NAME at LINE_NUMBER if CONDITION
Furthermore, you can also combine conditionals within your code and the use of keyboard to be able to interact with the code at a specific location.
for i=1:2:m-1
for j=1:2:n-1
if i == 505 && j == 460
keyboard % Now you can step through the "do stuff" below
end
% do stuff
end
end
As a side note, a REALLY useful debugging tip is to actually set dbstop to be triggered when ANY error is thrown.
dbstop if error
This will set a breakpoint right where any failure occurs. You can then use all the editor debugging tools or debugging commands (dbup, dbdown, dbstep, etc.) to go to where the real issue lies and look at the current state.
Question: Is there a preferred way to debug functions in matlab?
If I all calculations in a script, then every variable is in the workspace and I can easily query them to find out what's not working right. However, if I use a function, then only my outputs are visible and I can't see what's going wrong. I understand there are ways of getting around this, but thusfar they seem to be more trouble than just making one, long ugly, script. So how do YOU debug functions in matlab? Is there a preferred/efficient way of doing this?
I always make sure to enable "Stop If Error" in the Breakpoints menu and if I want to debug a specific function I set a breakpoint at the first line in that function (or at the point of interest). Note that "clear all", which is common in the beginning of scripts deletes all break points. Use "clear variables" instead.
See MATLAB settings - stop if errors for more info on how to make the Stop If Error persist when you restart Matlab.
I have an executable created with mcc. The .m file has a simple function that reads and plots values. After I run it from DOS, it freeze without returning execution to DOS. 2 questions:
1) How can i return execution to dos? I tried "return" and "exit" commands but didnt help
2) How to close the dos windows? is the only way to use a batch file or can I do it with a command in the .m file?
thanks
A.
There are 2 scenarii:
If your run your matlab executable from a DOS window, the DOS window will not get control back until the program terminates. If the program generate matlab figures (plot, surf, etc...), the program will not return to the console until all of the figures are closed.
You may think it is a waste for a simple plot, but after all your figure could be a evolved gui with a lot of code to execute. Or even a simple figure with a closeRequestFcn. So in Matlab terms, your program may still have instructions to execute as long as a figure is opened, so it will not return until it sure there is nothing more to do.
If you simply double clicked on your executable, the DOS looking console which open with your program will have the same behaviour. It will not disappear until the program returns (so until all your figures are closed if relevant).
I am not sure about linux, versions, but if you are running on windows, there is a way to suppress the DOS looking console for your graphic applications. Look at the -e switch in the mcc options.
This switch will compile your program in a way that no DOS console is opened when you double click on your executable.
So to summarize, I would recommend:
If your program is a 'command line' type (a function that takes input from the console and return values to the same). => Compile with normal options, and execute it from a DOS window (you do not want the window to disapear as soon as the program terminates.)
If your program is a gui or even simple plotting functions, with no need for console interactions, then compile with the -e switch and execute it by double clicking the .exe file.
note that in case you use the -e switch, it is recommended to direct potential output to a logfile. Look at the mcc documentation for more info.
edit
If you really need the DOS console and some graphic output, run your program form the command window with the following syntax:
start /b YourProgram
This will start the program in "background mode" (use YourProgram & in Linux terminal). You will be able to do anything in this console window, and you will also see the output from your matlab executable.
It can be confusing because the output from your program will be added to the simple dos prompt and you may think you do not have the control but if you type any command it will work. You can even start many program this way and retain control in your console, but all the output will arrive in the same window and they may be difficult to differentiate.
This question already has answers here:
Stop and continue execution from debugger possible?
(6 answers)
Closed 6 years ago.
In MATLAB, I'm running some code which takes a while to run. I'd like to pause the code to check on some variable values. Is there a way I can do this without having to re-run the code from the beginning? I don't want to terminate the program; just pause it.
You can halt execution and give a command prompt in two ways of which I am aware:
Putting keyboard in your code where you want to stop.
Setting a breakpoint.
You can resume and stop execution with dbcont and dbquit, respectively. To step forward, use dbstep. dbstack lets you see where you are. There are many more commands. The help page for any of these will give you other suggestions.
As Dennis Jaheruddin has pointed out, dbstop also has several useful features worth trying. In particular is the ability to set conditional and global (any line meeting a criterion) breakpoints via the dbstop if syntax. For example, dbstop if error will break to a debugging command prompt on any error. One suggestion he made, which I now do, is to put dbstop if error into startup.m so that this behavior will be default when you start MATLAB. You may need to create this file in a userpath folder; edit(fullfile(regexp(userpath,'^[^;]*','match','once'),'startup.m')).
One way to achieve what you're looking for would be to use code sections (also known as code cells), where you divide your code into sections divided by lines with two percent signs (%%).
Then, in the editor, you can press ctrl+enter to execute the current code section, and ctrl+up/down to navigate between sections.
Well there is the pause command, but then you cannot check for the variable contents in the workspace because the program is running.
What you probably want is to set a breakpoint (See the Debug menu / key F12).
At a breakpoint matlab pauses the program and enters debugging mode in which you can see and edit the variables. Once finished, you can resume the program where it was paused.
I'm not sure about Windows users but if you're running Linux you can start Matlab in a terminal using
matlab -nodesktop
then once Matlab has started, cd to your project directory and start your Matlab script. Now whenever you want to pause execution you can use ctrl-Z. Then to resume type fg. I hope this helps.
I wonder what the difference is between entering a few lines in the command window, or letting a script execute them.
In the question Escape from nested try - catch statement I have an example function. I have put the selected code in a script and called it, however then it does not work properly. On the other hand, when I
select the lines and hit f9, it works as expected.
The lines are:
dbclear all
dbquit
dbstop if caught error
I call the example function as such:
dbstop if caught error
mytestmain
And the example function is:
function mytestmain
try
mytestsub
catch
end
% Definition of subfunction, may or may not be in the same .m file
function mytestsub
try
a=b; %Intentionally generate an error as b is not defined
catch
end
I think it's related to MATLAB's just-in-time (JIT) compiler, which compiles functions before it runs them.
It seems that it compiles functions differently if dbstop is set or not (see here for reference). As it currently stands, MATLAB can not recompile a function while it is run (just try saving a changed function during a dbstop, and you will get a message informing you). As you can add and remove breakpoints during a dbstop I think you can also do so programmatically, but it should be impossible to "turn on" debugging if it wasn't turned on at "compile time"
So in your cases:
Using F9 it's just pasted and parsed as if you input it manually. So first dbstop is set, then mytestmain gets compiled and executed.
Running as a script will first compile the script and mytestmain and then execute it - so dbstop would be set after compilation and therefore not in effect.
Depending on what you mean by "doesn't work", it could just be because the debugger is a special context and certain debugger commands - dbup, dbdown, and dbquit - only work when you're at a debugger "K>>" prompt. Once you call a script, you're no longer at the debugger prompt but in normal code execution - inside a nested M-code call stack - and they just don't work there. When you F9, it does the lines individually, so each one is done from the prompt.
As a workaround, if you really want to execute a sequence of debugger commands like this, you could write a little Java Swing widget to enter the text in to the command window just as though you were typing it in.