Warning: Control Character '\Q' is not valid. fprintf

Hi there,

I searched all over and this seems to be an undocumented problem. At least not heavily documented.

I am trying to modify a txt file by reading it into a cell array with fgetl and then make changes to the relevant lines and finally write a txt file with the changes using fprintf. I get the warning in the subject and these lines are not written. these lines are paths.

What am I doing wrong? or what would be the right way to escape the problem? the files are attached. no need to run further than line 31 in main.m. The functions after that are not needed for my question.

Thanks a bunch, Asher

[Stephen23]

This is quite well documented in the fprintf documentation. Image Analyst has shown you the correct way to use fprintf, using a format specifier string (exactly as per the fprintf documentation): instead of this:

fprintf(fid,A{1,i});
fprintf(fid,'\n');

(which will throw an error with '\Q' and many other character combinations) you simply need to read the fprintf documentation, and use a format string:

fprintf(fid, '%s\n', A{1,i});

[Asher Metzger]

You're right it is documented. I just didn't understand it... Thanks a lot.

Answer 1

[Image Analyst]

You can print out a \Q if it's in a string. That's not the problem at all. The problem is that you don't have a format specifier string in your fprintf() statement. To fix, put '%s\n' in your fprintf().

fprintf(fid,'%s\n', A{1,i});

You don't need the second fprintf with just the backslash n because I combined it all into this single call to fprintf().

[Asher Metzger]

Thanks. Learning every day.