Replace lines in text file with different length line

Question

Andrei 2014-4-22

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https://ww2.mathworks.cn/matlabcentral/answers/126734-replace-lines-in-text-file-with-different-length-line

回答： Andrei 2014-4-23

Hi! I have a text file,something like that:

var1 = 1;

var2 = 20;

I have to replace the values after '=',but,if i replace '1' with '100', for example, text file looks like this: var1 = 100;var2 = 20; If i put '\n', text file look like this:

var1 = 100;

ar2 = 20;

I want it to look like:

var1 = 100;

var2 = 20;

I get the line with fgets,position with ftell, modify the line, go to the correct position in file with fseek, and then print the modified line with fprintf. Works if instead of '1' i want to put '3',for example,because they are the same length. I guess the string looks like: var1 = 1;\nvar2 = 20;,and when i replace '1' with '100' overwrites the string. Any ideea how can i do that?

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Answer 1

Joseph Cheng 2014-4-22

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You'll have to read in the whole file after where you want to insert and re-write it. At least to my knowledge there isn't a built-in matlab function to insert a chunk of data into a file and have everything after it shift over.

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Answer 2

Andrei 2014-4-23

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Ok,thank you. I don't want do to that because the file is big,but I guess there is no other way. I tried to add empty rows in file,but it's the same behaviour...