How to open a file and search for a specific parameter for it then change it and save and close?

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mostafa haggag 2018-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/396263-how-to-open-a-file-and-search-for-a-specific-parameter-for-it-then-change-it-and-save-and-close

回答： mostafa haggag 2018-4-20

hey so I got a Fortran file that I need to keep opening it for 400 times and keep changing two parameters inside of the file each time.i am planning to use fopen with write permission to do so.However, I am not sure what should I do next. I am not sure how things work when i am searching inside of a file thanks

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Answer 1

Jan 2018-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/396263-how-to-open-a-file-and-search-for-a-specific-parameter-for-it-then-change-it-and-save-and-close#answer_316239

编辑：Jan 2018-4-20

在 MATLAB Online 中打开

It is a very bad idea to modify a source code 400 times to modify a parameter. What about using a loop to modify the parameter inside the code? Compiling the Fortran code repeatedly is a waste of time.

But it is possible:

Str   = fileread(FileName);
CStr  = strsplit(Str, '\n');
Match = strncmp(CStr, 'Param =', 7);
CStr{Match} = sprintf('Param = %g', rand);
fid   = fopen(FileName, 'w');
if fid == -1
  error('Cannot open file: %s', FileName);
end
fprintf(fid, '%s\n', CStr{:});
fclose(fid);

This changes the line starting with "Param =".

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Answer 2

mostafa haggag 2018-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/396263-how-to-open-a-file-and-search-for-a-specific-parameter-for-it-then-change-it-and-save-and-close#answer_316268

thank you so much it is working I am running 200 simulations so I need to change this parameter 200 times to check what is happening using the 200 results. i know it would be easier to change the parameter using fortran but i need a new value for each simulation