sequential try catch end block for matlab

Question

I\'d like to run several lines of code, but I\'m unsure if any line will throw an error. If an error occurs however, I\'d like the script to ignore that line and continue on

Answer 1

A simpler approach involves reading the script file line by line and evaluating each line in turn. This assumes that the script you want to run does not include any multi-line statements (such as e.g. a for with the end on a different line, or a statement broken onto multiple lines using ...). This is a strong limitation, as it is common to e.g. initialize a matrix using multiple lines of text.

This is the function:

function execute_script(fname)
fid = fopen(fname,'rt');
n = 0;
while ~feof(fid)
   cmd = fgetl(fid);
   n = n+1;
   if ~isempty(cmd)
      try
         evalin('caller',cmd);
      catch exception
         disp(['Error occurred executing line number ',num2str(n),': ',exception.message]);
      end
   end
end

It does exactly as I described above: it reads in a line, then uses evalin to evaluate that line in the caller's workspace. Any variable created is created in the caller's workspace. Any variable used is taken from the caller's workspace.

For example, I create the file testscript.m with the following contents:

A = 1;
B = 2+C; % This line needs a variable not defined in the script!
D = 5;

Next, at the MATLAB command prompt:

>> execute_script('testscript.m')
Error occurred executing line number 2: Undefined function or variable 'C'.
>> whos
  Name      Size            Bytes  Class         Attributes

  A         1x1                 8  double                  
  D         1x1                 8  double                  

The variable A and D were created. If I define C:

>> C=0;
>> execute_script('testscript.m')
>> whos
  Name      Size            Bytes  Class         Attributes

  A         1x1                 8  double                  
  B         1x1                 8  double                  
  C         1x1                 8  double                  
  D         1x1                 8  double                  

With a variable C defined, the script runs without error, and defines B also.