fprintf with warning of a lone trailing backslash

19 views (last 30 days)
I have used matlab earlier but forgotten most of it. I have a bunch of scripts from earlier co-workers and there is some warnings. Probably because the code is from 2015-2017.
This code produces a warning 'A lone trailing backslash, ' \ ', is not a valid control character.
for m = 1:M
folderName = strcat(rootFolder,timeSteps(m+2).name,filesep);
fprintf(['\nProcessing folder', folderName]);
As I am 'new' to this it is hard for me to understand how I should fix it. I assumed the problem is '\n..', so I tried to remove that but I still get the warning and I am not sure what removing the \n does in this case. The script seems to work anyway, but I would like to know what is wrong.
Hope someone can help me

Accepted Answer

Image Analyst
Image Analyst on 29 Sep 2022
Like @Walter Roberson said, use fullfile, not strcat.
folderName = fullfile(rootFolder, timeSteps(m+2).name);
fprintf('Processing folder #%d of %d : "%s".\n', m, M, folderName);
Also see attached demo if you want to scan subfolders and do something to files in each subfolder.
  1 Comment
Andreas on 5 Oct 2022
Yes! This solution is best. Thanks a lot for suggesting fullfile and not strcat. Thank you all for being helpfull!

Sign in to comment.

More Answers (3)

VBBV on 28 Sep 2022
folderName = strcat(rootFolder,filesep,timeSteps(m+2).name);
fprintf(['\nProcessing folder %s', folderName]);
You need to interchange the filesep position to middle or center to distinguish names. Plus use the format specifier as well in fprintf
Andreas on 29 Sep 2022
I tried changing filesep. That gives me an error:
'Processing folder ../output/\002Error using imread>get_full_filename (line 570)
File "../output/\002DEM.tif" does not exist.'
So this solution does not work.
The best solution so far is
folderName = strcat(rootFolder,timeSteps(m+2).name, filesep);
fprintf('\nProcessing folder %s', folderName);

Sign in to comment.

Fangjun Jiang
Fangjun Jiang on 28 Sep 2022
Change to
fprintf(['\nProcessing folder %s', folderName]);
'\n' is fine, it produces a carriage return
Just need the '%s' to print the value of folderName.

Sign in to comment.

Jasmine Dhaliwal
Jasmine Dhaliwal on 12 Oct 2022
(I know your question is already answered, but since they mentioned that there's %d and %s, I wanted to make sure you also knew that there is %f for float numbers instead of doubles (%d)! How it works: You can specify how many digits and how many decimals you want with something like %4.2f, where 4 indicates a field width of 4 digits and .2 indicates how many decimals you want! In my class we really mainly used %0.2f iirc, so I certainly looked up the literature on what the first digit (4, in this case) meant, because I couldn't quite remember what it meant. As it is, I really couldn't tell you what "field depth" is, but hopefully this is helpful to you anyhow!
  1 Comment
Walter Roberson
Walter Roberson on 12 Oct 2022
the number before the % is the minimum field width. It is the target width for a column of numbers. The default is right jurisdiction within the column but the "-" flag requests left justification and the "0" flag requests zero padding on the left instead of space padding. The field will use more characters if necessary: it is common, for example, for people to forget to take into account the space for a negative sign.

Sign in to comment.


Find more on Search Path in Help Center and File Exchange




Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!