How to clear the last line in the command window

Question

I'm curious about the progress of the running program and I print some information about the current iteration such as:

for i = 1:N
    ...
    ...
    msg = sprintf('Processed %d/%d', i, N);
    display(msg)
end

I don't want to print the progress on separate lines, instead, I want the last line to replace the previous one. I don't want to use clc which clears all the content.

I know that '\b' can clear the last character (like backspace) and I can create a function with a for loop which clears the items till the previous new line before the last. But is there a better way to do that? If not, how can I check whether the last character on the command line is a new line or not?

Answer 1

I've looked at the problem, a while ago. And I've noticed that the character \r (used to erase the last line) works with matlab in command-line (-nodesktop) but not with the graphic mode...

The best solution I found is to do something like that:

n=0;
for ...
  ...
  fprintf(repmat('\b',1,n));
  fprintf(msg);
  n=numel(msg);
end

Answer 2

Yair Altman has a very nice example on his blog of how you can use the backspace control-character (\b) to do what you want but in an easier way than you were considering. Modifying your code to resemble his example, you could do something like this:

reverseStr = '';
for i = 1:N
    ...
    ...
    msg = sprintf('Processed %d/%d', i, N);
    fprintf([reverseStr, msg]);
    reverseStr = repmat(sprintf('\b'), 1, length(msg));
end

Answer 3

I use 'dispstat' function just for this purpose. It can update the previous output which is a missing function of default 'disp'. Very simple to use. It can be downloaded from here: http://www.mathworks.com/matlabcentral/fileexchange/44673-overwritable-message-outputs-to-commandline-window

***Sample usage:

 dispstat('','init'); % One time only initialization
 dispstat(sprintf('Begining the process...'),'keepthis','timestamp');
 for i = 97:100
     dispstat(sprintf('Progress %d%%',i),'timestamp');
     %doing some heavy stuff here
 end
 dispstat('Finished.','keepprev');

***Output:

11:25:37 Begining the process...
11:25:37 Progress 100%
Finished.

All the best