replacing multiple lines with multiple lines in ascii file

Hi

I would like to make a routine that can replace multiple lines with other multiple lines in a ascii file. This could for example be to replace 7 lines with 4 lines. I can not do it one line at the time because the single lines of the 7 lines are present other places in the file than in the 7 lines.

For single line replacement I have used

fin = fopen('in.txt','r');
fout = fopen('out.txt', 'w+');
while ~feof(fin)
  s = fgetl(fin);
  s = strrep(s, 'old string', 'newstring');
  fprintf(fout,'%s\n',s);
end
fclose(fin);
fclose(fout);

But I can't figure out an easy way to convert this to handle multiple lines replacement.

Do you have any ideas?

Thanks in advance.

Regards Brian.

Answer 1

[Jarrod Rivituso]

Can you read the whole file in and then just replace the strings?

wholeFile = fileread('myFile.txt');

newStr = 'This is the replacement for line 2 and 3';
oldStr = ['This is line 2' char(13) char(10) 'This is line 3'];

newFileData = strrep(wholeFile,oldStr,newStr);

fileID = fopen('newFile.txt','w')
fprintf(fileID,'%s',newFileData);
fclose(fileID)

Note that char(10) and char(13) are just line breaks and carriage returns.

[Brian Bak]

Hi Jarrod

Thank you that works.

I am trying to construct the newStr and oldStr variables from two text documents (original.txt and replace.txt) that contains several newStr and oldStr separated by a blank line.

original = fopen('original.txt','r');

replace = fopen('replace.txt','r');

wholeFile = fileread('wholeFile.txt');

NL = [char(13) char(10)]; % New line

s = '';

i = 1;

while ~feof(original)

j = 1;

while strcmp(s,' ') ~= 1

if j==1

s = fgetl(original);

org{i,1} = [s NL];

j=0;

else

s = fgetl(original);

org{i,1} = [org{i,1} s NL];

end

end

i = i+1;

s = '1';

end

Where

original.txt:

-----------------

first lines t

o be replaced

second lines

to be replaced

-----------------

replace.txt:

-----------------

first lines t

hat are repla

cing

second lines

that are repl

acing

-----------------

The strings for replace called rep are created in a similar way. The code makes one long string of every block that is separated by blank lines. For some reason it does not work when I try to use these strings in the string replace function strcmp.

fileID = fopen('newfile.txt','w');

for i = 1:length(rep)

newStr = rep{i};

oldStr = org{i};

if i == 1

newFileData = strrep(wholeFile,oldStr,newStr);

else

newFileData = strrep(newFileData,oldStr,newStr);

end

end

fprintf(fileID,'%s',newFileData);

fclose(fileID);

I think it is the way I construct the oldStr and newstr. Do you have any suggestions?

Thanks in advance

[Jarrod Rivituso]

Two thoughts

- strfind is helpful for finding strings. though, you may find even more use if you just again read the entire files in and then split them using regexp...

>> str = 'this is something, which is separated, by some commas'

>> regexp(str,',','split')

- When debugging stuff like this, i find it very useful to convert things to numeric and display their ascii values on the command prompt from time to time

>> str = sprintf('this is something \n which is separated \r\n by carriage returns and new lines')

>> double(str)

Answer 2

[Ken Atwell]

Have you considered regular expressions? the MATLAB function regexprep would probably do the trick:

old_str = [];
rep_str = [];
for i = 1:5
  old_str = [ old_str sprintf('Old Line %d\n', i) ];
end
for i = 2:3
  rep_str = [ rep_str sprintf('New Line %d\n', i) ];
end
new_str = regexprep(old_str, 'Old Line 2\W+Old Line 3\W+', rep_str);

The '\W+' is a bit of regular expression magic to match one or more whitespace characters, which is why it can span multiple lines.

Answer 3

[Brian Bak]

Hi

Thank you for your answers. I got it to work now.

clc;clear all;

original = fopen('original.txt','r'); % text blocks separated by empty line with one blank space
replace = fopen('replace.txt','r');% text blocks separated by empty line with one blank space
wholeFile = fileread('OLD_file.txt');
NL = [char(13) char(10)]; % New line

s = '';
i = 1;
while ~feof(original) 
    j = 1;
    while strcmp(s,' ') ~= 1
        if j==1
            s = fgetl(original);
            org{i,1} = [s NL];
            j=0; 
        else
            s = fgetl(original);
            if strcmp(s,' ') ~= 1
                org{i,1} = [org{i,1} s NL];
            end
        end
    end
    i = i+1;
    s = '1';
end

s = '';
i = 1;
while ~feof(replace) 
    j = 1;
    while strcmp(s,' ') ~= 1
        if j==1
            s = fgetl(replace);
            rep{i,1} = [s NL];
            j=0;
        else
            s = fgetl(replace);
          if strcmp(s,' ') ~= 1
            rep{i,1} = [rep{i,1} s NL];
          end
        end
    end
    i = i+1;
    s = '1';
end

fileID = fopen('NEWfile.txt','w');
for i = 1:length(rep)
    newStr = rep{i}; 
    oldStr = org{i};
    if i == 1
        newFileData = regexprep(wholeFile, oldStr, newStr,'once','ignorecase'); %strrep(wholeFile,oldStr,newStr);
    else
        newFileData = regexprep(newFileData, oldStr, newStr,'once','ignorecase'); %strrep(newFileData,oldStr,newStr);
    end
end
fprintf(fileID,'%s',newFileData);
fclose(fileID);

Best regards Brian