Error using exist "The optional second input to exist must be 'var', 'builtin','class', 'dir' or 'file' "

I don't understand why the following code doesn't work

for k = 1:4
% Create a text file name, and read the file.
	textFileName = ['A' num2str(k) '.txt'];
	if exist(textFileName, 'A')
		fid = fopen(textFileName, 'rt');
		mydata = fread(fid);
		fclose(fid);
	else
		fprintf('File %s does not exist.\n', textFileName);
	end
end

[Steven Lord]

What do you think this does or want it to do?

if exist(textFileName, 'A')

You expect this if condition to be satisfied if ... ?

Once we know that we may be able to help you write the correct command.

Answer 1

[Adam Danz]

It looks like you're checking the existance of a certain file named something like "A1.txt" on the matlab path prior to reading that file. The exist() function has 1 mandatory input and 1 optional input. The optional input allows you to specify the type of result to search for. If you're searching for a file, one of those option for the 2nd input is 'file'.

The correct way to search for the existance of that file on the matlab path is:

if exist(textFileName, 'file')

More info: https://www.mathworks.com/help/matlab/ref/exist.html#f5-453632-searchType