Writting multiple files with fopen 'w'

fileID = fopen('text\test.txt','w');

fprintf(fileID,'Comments:');

fclose(fileID);

Hi,

What can I do to not overwrite the previous file

There is a way for every time I run the script to make another file and not rewritte the old one, like test1.txt, test2.txt and so on?

[Stephen23]

https://blogs.mathworks.com/pick/2020/01/10/determining-next-available-file-name/

Answer 1

[Voss]

Here's a function (get_unused_file_name) you can use for this purpose. It takes a file name and check if that file already exists. If it does, the function appends '1' to the name and checks if that exists. If it does, it tries '2', and so on until it gets one that doesn't already exist, and returns that unused file name.

Here's a demonstration of it:

fn_orig = fullfile(pwd(),'text','test.txt') % file name to try

fn_orig = '/users/mss.system.Cr4l4C/text/test.txt'

mkdir('text')

% calling the function 4 times
for ii = 1:4
    
    fn = get_unused_file_name(fn_orig)
    
    % create the file so that next time around 
    % this file name is already taken:
    fid = fopen(fn,'w');
    fclose(fid);
    
end

fn = '/users/mss.system.Cr4l4C/text/test.txt'

fn = '/users/mss.system.Cr4l4C/text/test1.txt'

fn = '/users/mss.system.Cr4l4C/text/test2.txt'

fn = '/users/mss.system.Cr4l4C/text/test3.txt'

function file_name = get_unused_file_name(file_name)
[pn,fn,ext] = fileparts(file_name);
ii = 0;
while isfile(file_name)
    ii = ii+1;
    file_name = fullfile(pn,sprintf('%s%d%s',fn,ii,ext));
end
end

[Cristian Martin]

Thank you for answer, I'll will apply and come back to you for feedback!

[Cristian Martin]

fn_orig = fullfile(pwd(),'text','RT.txt'); % file name to try

mkdir('text');

for ii = 1:4

fn = newname(fn_orig);% create the file so that next time around this file name is already taken

fid = fopen(fn,'w');

fclose(fid);

end

After this part i receive this:

> In get_unused_file_name (line 3)

Attempt to execute SCRIPT get_unused_file_name as a function:

C:\Users\NewFolder\get_unused_file_name.m

Error in get_unused_file_name (line 5)

fn = get_unused_file_name(fn_orig);

and if I change get_unused_file_name in newname:

Warning: Directory already exists.

> In get_unused_file_name (line 3)

Undefined function or variable 'newname'.

Error in get_unused_file_name (line 5)

fn = newname(fn_orig);

[Voss]

Copy and paste the function get_unused_file_name (exactly as it is in my answer, including the function line) to a new m-file. Save the m-file as "get_unused_file_name.m".

Then you can use it like this:

fn = get_unused_file_name(fn_orig);

where fn_orig is the file you want to write to, and fn is the name of the actual file that will be used. Then use fn in your subsequent fopen call.

[Cristian Martin]

File get_unused_file_name:

function file_name = get_unused_file_name(file_name)

[pn,fn,ext] = fileparts(file_name);

ii = 0;

while isfile(file_name)

ii = ii+1;

file_name = fullfile(pn,sprintf('%s%d%s',fn,ii,ext));

end

end

Other file:

fn_orig = fullfile(pwd(),'text','test.txt'); % file name to try

for ii = 1:4

fn = get_unused_file_name(fn_orig);

fid = fopen(fn,'w');

fclose(fid);

end

fileID = fopen('fn','w','n');

fprintf(fileID,'Comments:');

fclose(fileID);

The error:

Undefined function or variable 'isfile'.

Error in get_unused_file_name (line 4)

while isfile(file_name)

Error in Untitled7 (line 4)

fn = get_unused_file_name(fn_orig);

I'll try again tomorrow, I guess I'm too tired :)

[Voss]

Looks like isfile was introduced in R2017b. Your version of MATLAB must be older than that. Try replacing that line:

while isfile(file_name)

with this:

while exist(file_name,'file')

And, by the way, in the "other file", you don't need to have the loop - that was just for demonstration to show how the function works. Going by the code in your original question, you can do something like this:

% fn_orig is the full path to test.txt, in directory 
% \text, a directory which must already exist under 
% the current working directory ( pwd() ):
fn_orig = fullfile(pwd(),'text\test.txt');

% fn is the file that will be written to:
fn = get_unused_file_name(fn_orig);

% write the file:
fileID = fopen(fn,'w');
fprintf(fileID,'Comments:');
fclose(fileID);

[Cristian Martin]

Indeed I use 2015a, and with exist its perfect functional. Now I get the ideea, but still I'm tired. Thank you for your patience and kindness!

[Voss]

You're welcome! Sorry about the snag with isfile, but I'm glad it's working now!