fprintf is printing strange characters instead of numbers

64 views (last 30 days)
I want to print a vector of unsigned integers to a text file, with a space between each number. But the file I get is just weird symbols. I must be doing some trivial mistake, it's not the first time it happens, I can't remember what could be the fix. It's happening on R2018b (but I remember it happening on older versions as well). Here's sample code below:
data = uint32(zeros(1, 1615));
data(1:2:50) = 1;
output = fopen('output.txt', 'wt');
fprintf(output, '%d ', data);
Output I get is: ‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‱‰‰‰‰‰‰‰‰‰‰ ...
Output I want is: 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 ...
Rik on 3 Oct 2018
That is why I came close to giving up, even for telling UTF-8 and windows-1252 apart, which should be relatively easy, but turns out to be non-trivial. Notepad++ seems to do a better job than what I can manage with Matlab.
For the files I'm using, my FEX submission works, but I have no idea how future-proof that function is (or past-proof for that matter).

Sign in to comment.

Accepted Answer

Guillaume on 3 Oct 2018
Edited: Guillaume on 3 Oct 2018
The problem is due to Notepad broken encoding detection algorithm. For some reason it assumes that the file is encoded in UTF16, where the byte sequence [49 32] (characters '1' and ' ' in ansi and UTF8) indeed represents the character '‱'. Note that simply adding a space, ' ', before your sequence of numbers completely change the behaviour of Notepad's detection algorithm. With a space at the start, it correctly interprets the file as ANSI or UTF8.
As Stephen said don't use notepad. It's broken (and very limited in functionality). A good alternative is the open source Notepad++. You can also simply use matlab's editor.
edit: another option would be to save your output.txt as UTF16, which would then be read correctly by notepad, particularly, if you insert a BOM at the beginning. However, while matlab can read/write UTF16, it's not documented so there may be some edge cases where it doesn't work appropriately. Additionally, notepad is probably the only software that tends to assume UTF16, everything else tends to assume UTF8 by default, so the display will look odd in almost every other text editor (matlab's included).

More Answers (0)





Community Treasure Hunt

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

Start Hunting!