I have 20 text files, and I want to use a matlab loop to get the last line of each file without taking into consideration the other lines. is there any matlab command to solve this problem?
One thing you can try is to open the text file as a binary file, seek to the end of the file, and read single characters (i.e. bytes) backwards from the end of the file. This code will read characters from the end of the file until it hits a newline character (ignoring a newline if it finds it at the very end of the file):
fid = fopen('data.txt','r'); %# Open the file as a binary
lastLine = ''; %# Initialize to empty
offset = 1; %# Offset from the end of file
fseek(fid,-offset,'eof'); %# Seek to the file end, minus the offset
newChar = fread(fid,1,'*char'); %# Read one character
while (~strcmp(newChar,char(10))) || (offset == 1)
lastLine = [newChar lastLine]; %# Add the character to a string
offset = offset+1;
fseek(fid,-offset,'eof'); %# Seek to the file end, minus the offset
newChar = fread(fid,1,'*char'); %# Read one character
end
fclose(fid); %# Close the file
On Unix, simply use:
[status result] = system('tail -n 1 file.txt');
if isstrprop(result(end), 'cntrl'), result(end) = []; end
On Windows, you can get the tail executable from the GnuWin32 or UnxUtils projects.
It may not be very efficient, but for short files it can be sufficient.
function pline = getLastTextLine(filepath)
fid = fopen(filepath);
while 1
line = fgetl(fid);
if ~ischar(line)
break;
end
pline = line;
end
fclose(fid);
Related
I am looping over a very large document to try and lemmatise it.
Unfortunately python does not seem to print to file for every line but run through the whole document before printing, which given the size of my file exceeds the memory...
Before I chunk my document into more bite-sized chunks I wondered if there was a way to force python to print to file for every line.
So far my code reads:
import spacy
nlp = spacy.load('de_core_news_lg')
fin = "input.txt"
fout = "output.txt"
#%%
with open(fin) as f:
corpus = f.readlines()
corpus_lemma = []
for word in corpus:
result = ' '.join([token.lemma_ for token in nlp(word)])
corpus_lemma.append(result)
with open(fout, 'w') as g:
for item in corpus_lemma:
g.write(f'{item}')
To give credits for the code, it was kindly suggested here: Ho to do lemmatization on German text?
As described in: How to read a large file - line by line?
If you do your lemmatisation inside the with block, Python will handle reading line by line using buffered I/O.
In your case, it would look like:
import spacy
nlp = spacy.load('de_core_news_lg')
fin = "input.txt"
fout = "output.txt"
#%%
corpus_lemma = []
with open(fin) as f:
for line in f:
result = " ".join(token.lemma_ for token in nlp(line))
corpus_lemma.append(result)
with open(fout) as g:
for item in corpus_lemma:
g.write(f"{item}")
How do I completely remove a line in Rust? Not just replace it with an empty line.
In Rust, when you delete a line from a file with the following code as an example:
let mut file: File = File::open("file.txt").unwrap();
let mut buf = String::from("");
file.read_to_string(&mut buf).unwrap(); //Read the file to a buffer
let reader = BufReader::new(&file);
for (index, line) in reader.lines().enumerate() { //Loop through all the lines in the file
if line.as_ref().unwrap().contains("some text") { //If the line contains "some text", execute the block
buf = buf.replace(line.as_ref().unwrap(), ""); //Replace "some text" with nothing
}
}
file.write_all(buf.as_bytes()).unwrap(); //Write the buffer back to the file
file.txt:
random text
random text
random text
some text
random text
random text
When you run the code, file.txt turns into this:
random text
random text
random text
random text
random text
Rather than just
random text
random text
random text
random text
random text
Is there any way to completely remove the line rather than just leaving it blank? Like some sort of special character?
This part is bad-news: buf = buf.replace(line.as_ref().unwrap(), "");
This is doing a search through your entire buffer to find the line contents (without '\n') and replace it with "". To make it behave as you expect you need to add back in the newline. You can just about do this by buf.replace(line.as_ref().unwrap() + "\n", "") The problem is that lines() treats more than "\n" as a newline, it also splits on "\r\n". If you know you're always using "\n" or "\r\n" as newlines you can work around this - if not you'll need something tricker than lines().
However, there is a trickier issue. For larger files, this may end up scanning through the string and resizing it many times, giving an O(N^2) style behaviour rather than the expected O(N). Also, the entire file needs to be read into memory, which can be bad for very large files.
The simplest solution to the O(N^2) and memory issues is to do your processing line-by-line, and
then move your new file into place. It would look something like this.
//Scope to ensure that the files are closed
{
let mut file: File = File::open("file.txt").unwrap();
let mut out_file: File = File::open("file.txt.temp").unwrap();
let reader = BufReader::new(&file);
let writer = BufWriter::new(&out_file);
for (index, line) in reader.lines().enumerate() {
let line = line.as_ref().unwrap();
if !line.contains("some text") {
writeln!(writer, "{}", line);
}
}
}
fs::rename("file.txt.temp", "file.txt").unwrap();
This still does not handle cross-platform newlines correctly, for that you'd need a smarter lines iterator.
Hmm could try removing the new line char in the previous line
Need some help, writing a program that will read the text from a file, but will
put at the beginning of each line a number, in such a way that each line is numbered in ascending order
example:
file1
a
b
c
What I want to see:
1: a
2: b
3: c
Process:
Read contents of file into a String
Split by line ending into Array<String>
Iterate and mutate contents line by line
Join by line ending back into a String
Write back into file
Sample code for any sys target:
var arr = sys.File.getContent('file.txt').split("\n");
for(i in 0...arr.length) {
arr[i] = (i+1) + ": " + arr[i];
}
sys.File.saveContent('file.txt', arr.join("\n"));
I want to copy elements of an array in a file txt. I read the first 50 samples of a wav file in array a and I want to copy a in a file txt. This is my code:
[s,fs]=wavread('file.wav');
for k=1:50
a=s(k)
end
fid = fopen('file.txt','wt');
fprintf(fid,'%f\n',a);
fclose(fid);
With this code in file txt there is only the last element of a, not all samples.
fprintf can process vector input. So you can simply replace the loop by a = s(1:50);:
[s,fs]=wavread('file.wav');
a = s(1:50);
fid = fopen('file.txt','wt');
fprintf(fid,'%f\n',a);
fclose(fid);
I want to read data from a file and save it into an array. Then insert some new data into this array and then save this new data back into the same file deleting what is already there. My code works perfectly, giving me my required data, when I have 'r+' in the fopen parameters, however when I write to the file again it does not delete the data already in the file just appends it to the end as expected. However when I change the permissions to 'w+' instead of 'r+', my code runs but no data is read in or wrote to the file! Anyone know why this might be the case? My code is as seen below.
N = 1021;
b = [0;0;0;0;0];
% Opens file specified by user.
fid = fopen('testing','w+');
% Read header data
Header = fread(fid, 140);
% Move to start of data
fseek(fid,140,'bof');
% Read from end of config header to end of file and save it in an array
% called data
Data = fread(fid,inf);
Data=reshape(Data,N,[]);
b=repmat(b,[1 size(Data,2)]);
r=[b ; Data];
r=r(:);
r = [Header;r];
% write new values into file
fwrite(fid,r);
fclose(fid);
% Opens file specified by user.
fid = fopen('test');
All = fread(fid,inf);
fclose(fid);
According to the documentation, the w+ option allows you to "Open or create new file for reading and writing. Discard existing contents, if any." The contents of the file are discarded, so Data and Header are empty.
You need to set the position indicator of the filehandle before writing. With frewind(fid) you can set it to the beginning of the file, otherwise the file is written / appended at the current position.
N = 1021;
b = [0;0;0;0;0];
% Opens file specified by user.
fid = fopen('testing','r+');
% Read header data
Header = fread(fid, 140);
% Move to start of data
fseek(fid,140,'bof');
% Read from end of config header to end of file and save it in an array
% called data
Data = fread(fid,inf);
Data=reshape(Data,N,[]);
b=repmat(b,[1 size(Data,2)]);
r=[b ; Data];
r=r(:);
r = [Header;r];
% write new values into file
frewind(fid);
fwrite(fid,r);
fclose(fid);
% Opens file specified by user.
fid = fopen('test');
All = fread(fid,inf);
fclose(fid);