How to edit specific lines of a large text file?

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Ehsan Fatourehchi 2017-3-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/331717-how-to-edit-specific-lines-of-a-large-text-file

编辑： Ehsan Fatourehchi 2017-4-7

Hi all, I have a large text file, about 7000 lines, and I need to read and edit specific lines, 300 lines, in the middle of the file. How can I skip unneeded lines?

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ES 2017-3-24

Some more details?

Do you know which specific line number, line content you should start editing?

Ehsan Fatourehchi 2017-3-24

Yes, I need to edit lines from 6600 to 6900. The start word of these lines is TEMP.

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Answer 1

dbmn 2017-3-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/331717-how-to-edit-specific-lines-of-a-large-text-file#answer_260221

在 MATLAB Online 中打开

If you already know the line number that you need to edit, I suggest to use one of the following solutions on matlabcentral https://de.mathworks.com/matlabcentral/answers/62986-how-to-change-a-specific-line-in-a-text-file

https://de.mathworks.com/matlabcentral/answers/38300-how-to-make-a-small-change-to-a-big-text-file-efficiently

If you dont know your line number yet, but know some test-marker (f.ex. TEMP....TEMP) you can read on the Matlab functions

regexprep
regexp

or check out this answer

https://de.mathworks.com/matlabcentral/answers/164931-how-to-parse-information-between-two-strings-using-regular-expressions

hope this helps.

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Ehsan Fatourehchi 2017-4-7

编辑：Ehsan Fatourehchi 2017-4-7

Thank you and Walter Roberson. I have finally made it by doing the following procedure: Identity the byte offsets of the values which needs to be changed. Then, each time, fopen asking for 'r+' access. fseek to the position, fwrite the new content, fclose. Since I have 900 different values to change, I created a matrix for byte offsets of the values beforehand.

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