how to modify a text file replacing an existing string with an user-defined string
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Hugo
am 13 Mär. 2013
Kommentiert: Narayanan Krishnamurthi
am 29 Apr. 2022
Hello,
I want to open an existing text file, modify it adding a string that I define and save the new file. The new string shall replace a string on the existing file, so I must identify it.
Any help appreciated, regards, Hugo
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Jos (10584)
am 11 Dez. 2013
fid = fopen('infile.txt','rt') ;
X = fread(fid) ;
fclose(fid) ;
X = char(X.') ;
% replace string S1 with string S2
Y = strrep(X, S1, S2) ;
fid2 = fopen('outfile.txt','wt') ;
fwrite(fid2,Y) ;
fclose (fid2) ;
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Walter Roberson
am 13 Mär. 2013
You cannot do this unless the replacement string is exactly the same length as the original string. Even then it is not recommended. Instead, create an output file, copy everything from the input until you reach the place you want to modify, write the new string without copying the old string, and then copy the rest of the old file to the new one. You can rename the new file to the old name if you need to afterwards.
2 Kommentare
Andreas Justin
am 11 Dez. 2013
Bearbeitet: Andreas Justin
am 11 Dez. 2013
Something like this?
%%Preparing
fid = fopen(fullfile('D:\','test.txt'),'w');
fprintf(fid,['function edit(str)',char(13), 'if nargin < 1 || isempty(str)',char(13),...
'str='''';',char(13),'end',char(13), 'rmpath(matlabroot);',char(13),...
'edit(str);',char(13), 'addpath(matlabroot);',char(13),'Matlab_extendEditorFunctionality(true);']);
fclose(fid);
clear fid
%%Reading
fid = fopen('D:\test.txt','r');
f = textscan(fid,'%s','Delimiter','\n');
txt = f{:};
%%manipulation
txt = regexprep(txt,'^function','\<FUNCTION\>')
txt = regexprep(txt,'path','\<PATH\>')
txt = regexprep(txt,'(.*)','$1\n');
txt = [txt{:}];
fclose(fid);
%%writing
fid = fopen('D:\test.txt','w');
fprintf(fid,txt)
fclose(fid);
1 Kommentar
Marco A. Acevedo Z.
am 17 Feb. 2022
Hello, this solution misses the tabulation spaces. That might be inconvenient for doing search and replace of XML files. On those specific cases use:
new_filename = ['new_' str2];
S = fileread(str2);
S = regexprep(S, 'µm', 'micron');
fid = fopen(new_filename, 'w');
fwrite(fid, S);
fclose(fid);
Cheers,
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