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How to make textscan robust against non-matching lines?

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I have files with lines that I want to parse, preferably with textscan. In between those lines, there may be lines to be skipped (unpredictable format and abundance, but definetely new lines). What is the best way to deal with it?
E.g. for the data in attachment, this will stop outputiing #HELLOMATHWORKS messages after line 4.
fid = fopen('data.txt');
out = textscan(fid,'#HELLOMATHWORKS,%[^,],%n');
fclose(fid);
This is a MWE out of a large code base.

Accepted Answer

Stephen Cobeldick
Stephen Cobeldick on 8 Apr 2021
Edited: Stephen Cobeldick on 9 Apr 2021
str = fileread('data.txt');
tkn = regexp(str,'#HELLOMATHWORKS,([^,]+),(\S+)','tokens');
tkn = vertcat(tkn{:})
tkn = 6×2 cell array
{'COM1'} {'2146'} {'COM1'} {'2147'} {'COM1'} {'2148'} {'COM1'} {'2149'} {'COM1'} {'2150'} {'COM1'} {'2151'}
vec = str2double(tkn(:,2))
vec = 6×1
2146 2147 2148 2149 2150 2151
  2 Comments
Stephen Cobeldick
Stephen Cobeldick on 9 Apr 2021
@Joan Vazquez: I presume that the text #HELLOMATHWORKS is not what is actually in your file. If the actual text contains some unique character that does not exist anywhere else in the file, you might be able to leverage the LineEnding/EndOfLine option to achieve the goal of reading the file data using textscan.

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More Answers (1)

Joan Vazquez
Joan Vazquez on 8 Apr 2021
This works, but it does not seem the best solution...Ideally, I would tell textscan "skip everything until a new line starts with #HELLOMATHWORKS"
filetext = fileread('data.txt');
expr = '[^\n]*#HELLOMATHWORKS[^\n]*';
% Find and return all lines that contain the text '#HELLOMATHWORKS'.
matches = regexp(filetext,expr,'match');
% Make it a 1xN char to feed textscan
goodlines = sprintf('%s\n', matches{:});
tmp = textscan(goodlines,'#HELLOMATHWORKS,%[^,],%n');

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