MATLAB: How to modify a text file replacing an existing string with an user-defined string

identify stringmodify stringmodify text filestring

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

Best Answer

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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MATLAB: How to convert ‘comma’ to ‘dot’

You can use my function fstrrep to replace each . with a , and then use dlmread to read the data:

fstrrep('test22.txt', ',', '.')
data = dlmread('test22.txt')

The m-file:

function fstrrep(filename, oldsubstr, newsubstr, newfilename)
%FSTRREP Replace string in file.
%


%FSTRREP(FILENAME, OLDSUBSTR, NEWSUBSTR, [NEWFILENAME])read each line in
%FILENAME and replaces the string OLDSUBSTR with NEWSUBSTR and writes the
%new line to NEWFILENAME. If the optional argument NEWFILENAME is not
%given, the contents of the original file is changed.
%
%Example: In file 'test.txt', replace each ',' with a '.'
%  fstrrep('test.txt', ',' '.')
%
%Thorsten.Hansen@psychol.uni-giessen.de
%%open file to read from and new file to write to
fid1 = fopen(filename, 'r');
if fid1 == -1
  error(['Cannot open file ' filename ' for reading.']);
end
if nargin < 4
  newfilename = '_temp.txt';
end
fid2 = fopen(newfilename, 'w');
if fid2 == -1
  error(['Cannot open file ' newfilename ' for writing.']);
end
%%read line and write changed line to new file
line = fgets(fid1);
while line ~= -1
  newline = strrep(line, oldsubstr, newsubstr);
  fprintf(fid2, '%s', newline);
  line = fgets(fid1);
end
%%close both files
st = fclose(fid1);
if st == -1
  error(['Cannot close ' filename '.'])
end
st = fclose(fid2);
if st == -1
  error(['Cannot close ' tempfilename '.'])
end
%%replace old file with new file
if nargin < 4
  movefile(newfilename, filename)
end

MATLAB: How to keep java file formatting after modification in Matlab using fprintf()

txt = fileread('A.java');
txt = regexprep(txt, 'V8_', 'V9_', 'once');
fid = fopen('A_mod.java', 'w');
fwrite(fid, txt);
fclose(fid);

Best Answer

Related Solutions

MATLAB: How to convert ‘comma’ to ‘dot’

MATLAB: How to keep java file formatting after modification in Matlab using fprintf()

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