How to pass multiple comment style to skip the header of a text file?

Question

kukushkin 2015-2-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/180407-how-to-pass-multiple-comment-style-to-skip-the-header-of-a-text-file

编辑： Nazar Adamchuk 2021-6-17

Hi I am pretty new to Matlab, so I need some help. I am trying to read a .txt file by skipping first couple lines (I do not know how many of them I need to skip beforehand). A sample data looks like the following:

<NUMBER OF ZONES 2
<NUMBER OF NODES> 4
<FIRST THRU NODE> 1
<NUMBER OF LINKS> 5
<END OF METADATA>
~ Init node Term node Capacity Length Free Flow Time BPower Speed limit Toll Type;
1    3    1  100 0.00000001   1000000000    1    0    0    1;
1    4    1  100   50    0.02    1    0    0    1; 
3    2    1  100   50    0.02    1    0    0    1;
3    4    1  100   10    0.1    1    0    0    1;  
4    2    1  100  0.00000001   1000000000    1    0    0    1;

So here, I would like to skip the lines starting with either < or ~. I am using the following codeline:

C = textscan(fid2, '%s' , 'Delimiter', ';', 'CommentStyle' , '<');

And I can skip the first 5 lines. However, I cannot skip the 6th one. I tried to pass multiple commentstyle but it gave an unknown error.

If someone can help me to not read the lines with ~ or <, I'd be glad.

PS: the sample file is easy to see, however, for other files I might not know where exactly the lines that I have to skip are.

Thanks in advance.

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Answer 1

Guillaume 2015-2-26

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https://ww2.mathworks.cn/matlabcentral/answers/180407-how-to-pass-multiple-comment-style-to-skip-the-header-of-a-text-file#answer_169351

在 MATLAB Online 中打开

I don't think textscan supports multiple comment style so you'll have to go a bit more low level:

fid = fopen('somefile', 'rt');
filepos = 0;
tline = fgetl(fid);
%read lines until end of file is reached (tline empty) or not a comment
while ~isempty(tline) & any(strncmp(tline, {'<', '~'}))
   filepos = ftell(fid);
   tline = fgetl(fid);
end
%the last line read was not a comment, rewind to its beginning
fseek(fid, filepos, 'bof');
%now use textscan, comments are already skipped
C = textscan(fid2, '%s' , 'Delimiter', ';', ');
fclose(fid);