How to delete a specific line from text file?

I got this text file:

3033011 Penelope_Cruz Cnm 99 88 77
404402 Gary_Cooper Bio 45 45 45
5055022 Tony_Curtis Dis 23 89 100
606603 Jim_Carrey Mng 100 100 100
7070000 Sandra_Bulloc Cnm 99 45 89
898989 Halle_Berry Bio 75 75 75

and I want to delete the 3rd line.

how can I do it?

Answer 1

[Walter Roberson]

You might notice that the below is not a nice little 3 or 5 line program. That is because the operating systems that MATLAB is supported on do not offer any method of deleting bytes in the middle of a file. The only real option is to copy the wanted text to another file and rename the files around.

Some of what is in this code is error checking and making sure that there is always an intact version of the file. If something goes wrong, you don't want to end up with a corrupted file. Always keep a backup version until you know the the deletion did what you wanted (and only what you wanted)

first_line_to_delete = 3;
num_lines_to_delete = 1;

infilename = 'YourFile.txt';
[pathstr, file, ext] = fileparts(infilename);
backfile = fullfile(pathstr, [file '.bak']);

if strcmp(infilename, backfile)
  error('I refuse to edit a backup file! Nothing has been changed.');
end

outfile = tempfile;   %a temporary file in TMP directory

fin = fopen(infilename, 'r');
if fin < 0; error('Input file does not exist'); end 
fout = fopen(tfile, 'w');
if fout < 0
  fclose(fin);
  error('Could not open temporary output file');
end

%read lines before the one to be deleted and write them to output
for K = 1 : first_line_to_delete - 1;
  inline = fgets(fin);
  if ~ischar(inline); break; end;  %end of file?
  fwrite(fout, inline);
end

for K = 1 : num_lines_to_delete
  if ~ischar(inline); break; end   %in case EOF
  inline = fgets(fin);   %and do nothing with it
end

%copy all remaining input lines to output file
while ischar(inline)
  inline = fgets(fin);
  if ischar(inline)   %not if we hit EOF
    fwrite(fout, inline);
  end
end

fclose(fin);
fclose(fout);

%M'Kay, we did the copying and have a file with the desired
%result. Now put it in the proper place

status = movefile(infilename, backfile);
if ~status
  if strcmp(infilename, backfile)
    fprintf(2, 'Good thing your programmer is paranoid about people overriding\nsanity checks, because something went wrong and you nearly lost your file!\n');
  else
    delete(backfile);
  end
  error('Could not rename file to .bak, file left untouched');
else
  status = movefile(outfile, infilename);
  if ~status
    error( ['Could not rename temp file to original name, original moved to ', backfile]);
  end
end

[ben velt]

I think your way is too complicated, and when I tried it there were some errors.

Maybe you can help in another way, first I do this:

fileID = fopen('List.txt', 'r', 'n', 'US-ASCII');
dataTABLE = textscan(fileID, '%f%s%s%f%f%f%[^\n\r]', 'Delimiter', ' '); 
fclose(fileID);
id = dataTABLE{:, 1};
firstname_lastname = dataTABLE{:, 2};
department = dataTABLE{:, 3};
firstgrade = dataTABLE{:, 4};
secondgrade = dataTABLE{:, 5};
thirdgrade = dataTABLE{:, 6};

And then I got this cell array "dataTABLE". I know the lines that I want to delete so maybe there is a way to delete it from "dataTABLE" and then export it to the same 'List.txt' file?

if its not good than ill try to understand your solution.

thanks ahead!!

[Walter Roberson]

Where I had

outfile = tempfile;

it should be

outfile = tempname;

[ben velt]

Undefined function or variable 'tfile'. Error in Untitled2 (line 12) fout = fopen(tfile, 'w'); >>

[Walter Roberson]

You have to decide whether you are deleting a line from a file or a record from a table.

The code I gave should (unless there are bugs) be able to delete a (series of) lines from any text file that is line-oriented (lines ending in newline characters), leaving everything else about the contents exactly as-is. It could be applied to (for example) your thesis file or other irregular files. If there was a place in your file that had two spaces that only "needed" one, the code would leave those two spaces intact, changing nothing other than leaving out the lines specified.

If you want to delete an entry from a table, then it is "fair game" to interpret the data and rewrite it, possibly changing the spacing or the number of decimal places or the column delimiter when you do so.

[ben velt]

I guess I didnt explained myself very well. My program is like this- Im opening the List.txt file with matlab into a cell array table. Then I need to decide if I want to delete someone from this table. After I delete from the cell array the cells that I dont need, I need to change the List.txt file also, according to the changes I did.

[Walter Roberson]

Then you don't have to worry about deleting lines from text files: just delete the cells from the table and then write out the table.

Answer 2

[per isakson]

An alternate approach

function    cssm( )
    str = fileread( 'cssm.txt' ); 
    pos = strfind( str, sprintf('\n') );
    str( pos(2)+1 : pos(3) ) = [];
    fid = fopen( 'cssm1.txt', 'w' );
    fprintf( fid, '%s', str );
    fclose( fid );
end

Tested on R2013a