Replace specific line in a text file

Question

Islam Elnady 2019-10-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/487315-replace-specific-line-in-a-text-file

编辑： Islam Elnady 2019-10-26

采纳的回答： Shubham Gupta

在 MATLAB Online 中打开

Hi everyone,

I have a text file (for example: data.dat) as shown below, with a number of lines.

data.dat
@motion parameters
speed= 22,30,60
range= 600
rotation= 50
@controls
act= 2,3,4,5

I want to read it and replace the line that comes right after the line starting with a specfic keyword e.g. "@controls" . In this case, the line to be replaced is this one

act= 2,3,4,5

and it should be changed in a loop. For an instant, for example, it would change to:

act= 1,0,8,-2

I'd appreciate your help. Thanks in advance.

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Answer 1

Shubham Gupta 2019-10-25

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/487315-replace-specific-line-in-a-text-file#answer_398158

在 MATLAB Online 中打开

One of the way could be:

fid = fopen('data.dat','r');        % Open File to read
replaceline = 'act= 1,0,8,-2';      % Line to replace
i = 1;
tline = 's';
A = {[]};
while ischar(tline)
    tline = fgetl(fid);
    if ~isempty(strfind(tline,'@controls')) % find '@controls'
        A{i}=tline;
        A{i+1} = replaceline;               % replace line
        tline = fgetl(fid);
        i = i+1;
    else
        A{i}=tline;
    end
    i = i+1;
end
fclose(fid);
fid2=fopen('data.dat','w');            % Open file to write
for i=1:length(A)-1
    fprintf(fid2,['%s',char([13,10])],A{i});
end
fclose(fid2);

Let me know if you have doubts !

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Islam Elnady 2019-10-26

编辑：Islam Elnady 2019-10-26

在 MATLAB Online 中打开

Thank you for help. It worked perfect. But when I changed

A{i+1} = replaceline;

to

A{i} = replaceline;

So that I could replace the same line. If there is a line below the repleaced one, it'll be deleted and replaced with a blank line. What edits should be made to fix this?

Islam Elnady 2019-10-26

编辑：Islam Elnady 2019-10-26

在 MATLAB Online 中打开

while ischar(tline)
    tline = fgetl(fid);
    if ~isempty(strfind(tline,'@controls'))  % find '@controls'
        A{i}=tline;
        A{i} = replaceline;               % replace line
      %  tline = fgetl(fid);
      %  i = i+1;
    else
        A{i}=tline;
    end
    i = i+1;
end