Write a substring in a Text file with existing string

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Saeed Soltani 2016-5-30

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编辑： Saeed Soltani 2016-6-2

Hi, I would like to write a word in the following of an existing string in text file, but with my code it deletes the whole and write the new word.

         fid = fopen('File.text','w');
         fprintf(fid,'%s', NewWord);

I just need to find end of line, and add the new word with only one space to the rest. Should I use textscan or?

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Answer 1

Stephen23 2016-5-30

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编辑：Stephen23 2016-5-30

在 MATLAB Online 中打开

Change the fopen file permission from 'w' (write) to 'a' (append):

fid = fopen('File.text','at');

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Saeed Soltani 2016-5-30

在 MATLAB Online 中打开

First I have to say, not only it does not make the space, but also some time it goes to the next line. That must not happen because my parsing pattern will affect.

About what I am doing:

I have a dynamic GUI tool, it gets new word and run some functions, and additionally it must insert this name to a text file. Then from other part of my GUI I have a listbox that must be updated. It parses the whole text file and base on a pattern (space + \ + Word) extract all “Words” to the list box. Actually I want to update my listbox based on the updated text file. Here is the code (parsing part) of push button which update the listbox:

function pushbutton1_Callback(hObject, eventdata, handles)
filecontent = fileread('ECUNames.text');
scchildren = regexp(filecontent, '(?<=/)\w+\s', 'match')
A = length(scchildren);
listboxItems1 = scchildren(1:A);
set(handles.listbox1,'String', listboxItems1 );

One thing that I noticed, the error I told you, only happens when I click the button directly from the GUI. But If I run the code (.m file) it updates the listbox of GUI without error.

Thank you in advance for your time and help

Stephen23 2016-5-30

编辑：Stephen23 2016-5-30

在 MATLAB Online 中打开

"it does not make the space" you can easily add this in your fprintf call:

fprintf(fid,' %s', NewWord);

Newlines are not added by this code. If there are newlines in the file then they are part of the strings that are being passed to fprintf, or were in the file beforehand. You might also be getting confused by what a text editor displays: word wrapping is not the same as a newline character.

MATLAB does not display infinite amount of information in the variable summary: when the content of cell is a non-scalar numeric, or a string longer than some length, then it is displayed only with meta-information (its class and size) instead of its content:

>> C = {'abc','defghijklmnopqrstuvwxyz','abcdefgh','i','jklmn','opqrstuvwxyz'}
C = 
    'abc'    [1x23 char]    'abcdefgh'    'i'    'jklmn'    'opqrstuvwxyz'
>> C{2} % See, the string is still there!
ans =
defghijklmnopqrstuvwxyz

Note that a neater and faster way of passing data between GUI callbacks is to use guidata. You will find the recommended methods described here:

http://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

I have no idea why "Attempt to reference field of non-structure array" happens, because you did not give us the complete error message.

Stephen23 2016-5-31

MATLAB reads fucntion files once and then stores them in memory. This makes them faster (and I guess some JIT optimization occur too). What you are trying to do is to dynamically change MATLAB code, which is not a recommended way of using MATLAB, because it is slow and buggy.

Saeed Soltani 2016-6-2