How do you specify special character using ASCII code in a textscan format string?

I have a file that contains special characters (ASCII codes 02 and 03) I would like to parse. The problem is I cannot find how to specify these characters in the textscan format string.

I can load the file with the following code:

data = textscan(fid,'%s','WhiteSpace',char(3),'EndOfLine','')

But I would like to include this character in the format string to directly parse data.

The format string I'd like to write could look like:

data = textscan(fid,'\x02%s\r\nR,%f,%f\r\nL,%f,%f\r\n\x03')

where \x02 and \x03 would specify ASCII codes 2 and 3.

Below is a snapshot of my file in Notepad++:

Thanks for your help.

Answer 1

[Stephen23]

The task of encoding non-printing characters by writing printing characters is typically solved by using special characters. In this case though, there no escaped/special characters to represent ASCII chars 2 and 3.

A general solution would be to use sprintf to specify the format string:

>> fmt = sprintf('%s%%s\\r\\nR,%%f,%%f\\r\\nL,%%f,%%f\\r\\n%s',2,3)
fmt =
  %s\r\nR,%f,%f\r\nL,%f,%f\r\n
>> +fmt % checking
ans =
  2    37   115    92   114    92   110    82    44    37   102    44    37   102    92   114    92   110    76    44    37    102    44    37   102    92   114    92   110     3

Although given the locations of those special characters, you could simply concatenate them onto the ends of the string:

 fmt = [char(2),'%s\r\nR,%f,%f\r\nL,%f,%f\r\n',char(3)];

Note if you fopen the file using the t option, then it is not required to specify both \r and \n for each newline as this gets converted to a single newline:

fid = fopen(...,'rt'); % note the "t" !
out = textscan(fid,[char(2),'%s\nR,%f,%f\nL,%f,%f\n',char(3)]) % \r not required
fclose(fid)

This makes your code multi-platform and easier to write. I would highly recommend using the t option when reading text files.

[Guillaume]

fmt = sprintf('\x02%%s\\r\\nR,%%f,%%f\\r\\nL,%%f,%%f\\r\\n\x03');

would also work. But more readable would be:

fmt = sprintf('\x02%s\x03', '%s\r\nR,%f,%f\r\nL,%f,%f\r\n')

which avoids having to double the \ and %