How to read any file by using txt ?

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Muharrem Askin 2012-5-22

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https://ww2.mathworks.cn/matlabcentral/answers/39006-how-to-read-any-file-by-using-txt

I have a file which is different than txt file but I would like to read it as txt file. It is like right clicking to the icon and choosing 'open with txt' section. I would like to do in matlab and change some parameters inside the txt file. Thanks

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Answer 1

Geoff 2012-5-22

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在 MATLAB Online 中打开

The only difference between reading a binary file versus a text file is to translate end-of-line characters. Other than that (and implicitly, the types of characters you get in text versus binary), there's no difference. I would recommend you read the file as binary.

Unless you're saying that it is ACTUALLY a text file but just has a different file extension. Then I would recommend opening in text mode as per usual.

To open in binary mode:

fid = fopen( 'myfile.dat', 'rb' );
allbytes = fread(fid);    % this call reads all characters from the file
fclose(fid);

To open in text mode:

fid = fopen('myfile.dat', 'rt' );
line = fgetl(fid);        % this call reads a single line from the file
fclose(fid);

Have a look at this:

http://www.mathworks.com/help/techdoc/matlab_prog/f10-61355.html

[EDIT] From your example...

infile = fopen( 'myfile.$PJ', 'rt' );
outfile = fopen( 'myfile_processed.$PJ', 'wt' );
while ~feof(infile)
  line = fgetl(infile);
  toks = textscan(line, '%s%f', 1);
  if ~isempty(toks)
    switch toks{1}
      case {'HEIGHT', 'HOFFST', 'TOWHT'}
        line = sprintf( '%s %d', toks{1}, fix(toks{2}+1) );
    end
  end
  fprintf( outfile, '%s\n', line );
end
fclose(infile);
fclose(outfile);

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Muharrem Askin 2012-5-31

Maybe the infile and outfile should be the same file. Then I can skip reading and writing of the irrelevant to another outfile and I can only make some changes inside the original file.

Geoff 2012-5-31

Oh, I was out by one level of indirection =( The tokens are returned as a cell array, and the string in the first cell is itself a cell... So you need something like:

if ~isempty(toks) && iscell(toks{1})

Then you need to turn all the toks{1} references into toks{1}{1}

You could've worked this out by reading that error message and using the debugger! =P Don't give up and think of crazy alternative solutions just because there is an error in the code. I wrote that code into a web browser as a rough guide for you to follow.

As for reading and writing the same file, I wouldn't recommend it... But yes, you can, and in your case you would have to make sure you are replacing exactly the same number of bytes which may involve replacing some with spaces... The problem comes when you want to insert a number that is longer, and you need to shuffle all the rest of the bytes in the file.... So please don't go and make your problem more complicated than it needs to be. If you don't follow this piece of advice, then run into trouble and ask me to help, you'll be disappointed! =)

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