Text File I/O Question

Question

Berk Öztürk 2022-12-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1884772-text-file-i-o-question

评论： Voss 2022-12-27

Question : Write a function called char_counter that counts the number of a certain character in a text file. The function takes two input arguments, fname, a char vector of the filename and character, the char it counts in the file. The function returns charnum, the number of characters found. If the file is not found or character is not a valid char, the function return -1. As an example, consider the following run. The file "simple.txt" contains a single line:"This file should have exactly three a-s..." ,

charnum = char_counter('simple.txt,'a')

charnum =

3

My code is below and passed all tests but I want to know if there is a pitfall in my code or a way to do it smarter. Thanks in advance.

function charnum = char_counter(fname,character)

charnum = 0;

if ischar(character)==0

charnum=-1;

return;

end

fid=fopen(fname,'rt');

if fid<0

charnum = -1;

return;

end

oneline = fgets(fid);

while ischar(oneline)

for ii=1:length(oneline)

if oneline(ii)==character

charnum = charnum + 1;

else

continue;

end

oneline = fgets(fid);

end

fclose(fid);

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Voss 2022-12-27

在 MATLAB Online 中打开

The

else
    continue;

block is unnecessary.

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Answer 1

Voss 2022-12-26

0
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https://ww2.mathworks.cn/matlabcentral/answers/1884772-text-file-i-o-question#answer_1136622

在 MATLAB Online 中打开

You don't need to go line-by-line and character-by-character, you can read the entire file at once and count the total number of occurrences of character like this:

charnum = nnz(fread(fid,'*char') == character);

If you do that, your function might look something like this:

function charnum = char_counter(fname,character)
if ~ischar(character) || ~isscalar(character)
    charnum = -1;
    return
end
fid = fopen(fname,'rt');
if fid < 0
    charnum = -1;
    return
end
charnum = nnz(fread(fid,'*char') == character);
fclose(fid);