I have created a function that allows copying a number of lines from a text file and create a new file, let's say I want to take only the data contained between $$ElmLodlv and $$ElmNet.
Here is the code
fID = fopen(fileName,'r');
tline=fgetl(fID) ;
while isempty (strfind(tline,'$$ElmLodlv'))
tline=fgetl(fID) ;
end
buffer = fread(fID,Inf) ;
fclose(fID) ;
fID=fopen(newFileName,'w');
fwrite(fID, buffer) ;
fclose(fID);
end
The thing is that I don't really know how can I stop my buffer in the line corresponding to $$ElmNet, In other words my function creates a new file from $$ElmLodlv to the end of the file.
Any ideas how can do this?
What about an alternative to fread(fID,Inf):
buffer=0;
while ~feof(fID)
tline=fgetl(fID);
if ~isempty (strfind(tline,'$$ElmNet'))
break;
end
buffer(end+1:end+2+length(tline))=[tline 13 10];
end;
buffer=buffer(2:end);
Note that [13 10] equals to \n in the code above.
hope it helps!
Related
So I have to modify a .dxf file (an Autocad file) by changing some data in it for another one we choose previously. Changing some lines of a .txt file in Matlab is not pretty difficult.
However, I cannot change a specific line when the new input's length is larger than the old one.
This is what I have and I want to change only 1D57:
TEXT
5
1D57
330
1D52
100
AcDbEntity
8
0
If I have as an input BBBB, everything goes right since both strings have the same length. The same does not apply when I try with BBBBbbbbbbbbbb:
TEXT
5
BBBBbbbbbbbbbb2
100
AcDbEntity
8
0
It deletes everything after it until the string stops. It happens the same when the input is shorter: it does not change the line for the new string but it writes until the new input stops. For example, in our case with AAA as an input, the result would be AAA7.
This is basically the code I am using to modify the file:
fID = fopen('copia.dxf','r+');
for i = 1:2
LineToReplace = TextIndex(i);
for k = 1:((LineToReplace) - 1);
fgetl(fID);
end
fseek(fID, 0, 'cof');
fprintf (fID, [Data{i}, '\n']);
end
fclose(fID);
You need to overwrite at least the rest of the file in order to change it (unless exact number of characters is replaced), as explained in jodag's comment. For instance,
% String to change and it's replacement
% (can readily be automated for more replacements)
str_old = '1D52';
str_new = 'BBBBbbbbbbbbbb';
% Open input and output files
fIN = fopen('copia.dxf','r');
fOUT = fopen('copia_new.dxf','w');
% Temporary line
tline = fgets(fIN);
% Read the entire file line by line
% Write it to the new file
% Replace str_old with str_new when encountered - note, if there is more
% than one occurence of str_old in the file all will be replaced - this can
% be handled with a proper flag
while (ischar(tline))
% char(10) is MATLAB's newline character representation
if strcmp(tline, [str_old, char(10)])
fprintf(fOUT, '%s \n', str_new);
else
% No need for \n - it's already there as we're using fgets
fprintf(fOUT, '%s', tline);
end
tline = fgets(fIN);
end
% Close the files
fclose(fIN);
fclose(fOUT);
% Copy the new file into the original
movefile 'copia_new.dxf' 'copia.dxf'
In practice, it is often far easier to simply overwrite the whole file.
As written in the notes - this can be automated for more replacements and it would also need an additional flag to only replace a given string once.
I have a data file that contains parameter names and values with an equal sign in between them. It's like this:
A = 1234
B = 1353.335
C =
D = 1
There is always one space before and after the equal sign. The problem is some variables don't have values assigned to them like "C" above and I need to weed them out.
I want to read the data file (text) into a cell and just remove the lines with those invalid statements or just create a new data file without them.
Whichever is easier, but I will eventually read the file into a cell with textscan command.
The values (numbers) will be treated as double precision.
Please, help.
Thank you,
Eric
Try this:
fid = fopen('file.txt'); %// open file
x = textscan(fid, '%s', 'delimiter', '\n'); %// or '\r'. Read each line into a cell
fclose(fid); %// close file
x = x{1}; %// each cell of x contains a line of the file
ind = ~cellfun(#isempty, regexp(x, '=\s[\d\.]+$')); %// desired lines: space, numbers, end
x = x(ind); %// keep only those lines
If you just want to get the variables, and reject lines that do not have any character, this might work (the data.txt is just a txt generated by the example of data you have given):
fid = fopen('data.txt');
tline = fgets(fid);
while ischar(tline)
tmp = cell2mat(regexp(tline,'\=(.*)','match'));
b=str2double(tmp(2:end));
if ~isnan(b)
disp(b)
end
tline = fgets(fid);
end
fclose(fid);
I am reading the txt file line by line, and using general expressions to get rid of useless chars, and then converting to double the value read.
I have a text file with two columns of data. I want to split this file and save it as two individual strings in matlab, but I also need to stop copying the data when I meet an identifier in the data then stat two new strings.
For example
H 3
7 F
B B
T Y
SPLIT
<>
Where SPLIT <> is where I want to end the current string.
I'm trying to use fopen and fscanf, but struggling to get it to do what I want it to.
I tried the following script on the example you provided and it works. I believe the comments are very self explanatory.
% Open text file.
fid = fopen('test.txt');
% Read the first line.
tline = fgetl(fid);
% Initialize counter.
ii = 1;
% Check for end string.
while ~strcmp(tline, 'SPLIT')
% Analyze line only if it is not an empty one.
if ~strcmp(tline, '')
% Read the current line and split it into column 1 and column 2.
[column1(ii), column2(ii)] = strread(tline, ['%c %c']);
% Advance counter.
ii = ii + 1;
end
% Read the next line.
tline = fgetl(fid);
end
% Display results in console.
column1
column2
% Close text file.
fclose(fid);
The key functions here are fgetl and strread. Take a look at their documentation, it has some very nice examples as well. Hope it helps.
I have a flat file saved in binary format, i want to seek to specific byte and read untile the end of that file, so we need a condition for that, what is the condition that indicates the end of the file?
By the way, i don't want to load the whole file just open the file and seek to the position i need then read until to the end of the file...
MATLAB's fread function (and, indeed, the other file IO functions) will automatically detect the end of a binary file; there's no need for a special end-of-file marker.
fread documentation
General MATLAB IO documentation
You can use feof to test for the end of a file. For example, to read a file one character at a time:
fid = fopen('bench.dat');
k = 0;
while ~feof(fid)
curr = fscanf(fid,'%c',1);
if ~isempty(curr)
k = k+1;
benchstr(k) = curr;
end
end
fclose(fid);
You can pass Inf for the size argument when using the FREAD function (will read until end of file). Here is an example:
%# first lets create a simple binary file
fid = fopen('file.bin', 'wb');
fwrite(fid, 'hello world', 'char*1');
fclose(fid);
%# now open binary file, seek to some position, and read bytes till EOF
fid = fopen('file.bin', 'rb');
fseek(fid, 6, 'bof'); %# go to the 7th byte
B = fread(fid, Inf, 'uint8=>char'); %# read bytes until end-of-file (as chars)
fclose(fid);
disp(B)
In Matlab, after creating a certain number of lines and printing them to a file, I have the need to delete a line and rewrite the rest of the data to that same file. When I do so, the new data overwrites the previous data, but since the data is shorter than the original, there are still remnants of the original data. Does anyone have any idea what the best/most efficient way to delete that extra data is?
Here is a simplified example of what I'm trying to do:
fid = fopen('file.txt','w');
for i=1:10
fprintf(fid,'%i\r\t',i);
end
frewind(fid);
for i=3:5
fprintf(fid,'%i\r\t',i);
end
fprintf(fid,'EOF');
fclose(fid);
I've looked all over, but I can't seem to find the solution to my question. Any suggestions?
Without using any temp files, you can do the following:
fid = fopen('file.txt', 'wt');
for i=1:10
fprintf(fid, '%i\n', i);
end
frewind(fid);
for i=3:5
fprintf(fid, '%i\n', i);
end
pos = ftell(fid); % get current position in file
fclose(fid);
% read from begining to pos
fid = fopen('file.txt', 'r');
data = fread(fid, pos);
fclose(fid);
% overwite file with data read
fid = fopen('file.txt', 'w');
fwrite(fid, data);
fclose(fid);
Printing "EOF" won't work - nice try!
There are Unix system calls truncate and ftruncate that will do that, given either a file descriptor (truncate) or handle (ftruncate) in the first argument and a desired length in the second.
I'd try and see if Matlab supports ftruncate. Failing that... if worst came to worst you could copy-write the file to a new file, stopping and closing the new file when you hit what you consider the end of data.
To follow up on Carl Smotricz's suggestion of using two files, you can use MATLAB's DELETE and MOVEFILE commands to avoid system calls:
fid = fopen('file.txt','wt');
for i=1:10
fprintf(fid,'\t%i\r',i);
end
fclose(fid);
fid = fopen('file.txt','rt');
fidNew = fopen('fileNew.txt', 'wt');
for i = 1:2
s = fgetl(fid);
fprintf(fidNew, '%s\r', s);
end
for i=4:10
fprintf(fidNew, '\t%i\r', i);
end
fclose(fid);
fclose(fidNew);
delete('file.txt');
movefile('fileNew.txt', 'file.txt')