MATLAB Answers

check if a file exists

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Salvatore Mazzarino
Salvatore Mazzarino on 29 Sep 2012
Commented: sesilia maidelin on 22 Jul 2021 at 9:53
I'm using the "importdata" function to import data from a text file. I would like to have a way to check if the text file exists before attempting to import data from the file. If the file doesn't exist, I would then like to display a custom error message. What is the function that I should use?

Accepted Answer

Jan
Jan on 29 Sep 2012
Edited: MathWorks Support Team on 9 Nov 2018
Starting in R2017b, you can use the "isfile" function to check if a file exists. For example:
if isfile(filename)
% File exists.
else
% File does not exist.
end
The "isfile" function searches for files only on the specified path or in the current folder.
For R2017a and previous releases, use the "exist" function. For example:
if exist(filename, 'file') == 2
% File exists.
else
% File does not exist.
end
Be sure to specify an absolute path for the file name. The "exist" function searches all files and folders on the search path, which can lead to unexpected results if multiple files with the same name exist.
  5 Comments
sesilia maidelin
sesilia maidelin on 22 Jul 2021 at 9:53
hi there, thanks for replying @Jan , in my case i just want to know the existence of a particular file type in a folder, then move the folder to another parentfolder named complete. so if the folder AAA contains a .txt and .jpgs, i want to move AAA into the folder complete that contains folder AAZ, BBA, etc that also contain .txt and .jpg files. i attached the picture of how the source file look like. I want to move files like 00000715 to the folder complete. Thank you!

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More Answers (5)

Image Analyst
Image Analyst on 29 Sep 2012
if exist(fullFileName, 'file')
% File exists. Do stuff....
else
% File does not exist.
warningMessage = sprintf('Warning: file does not exist:\n%s', fullFileName);
uiwait(msgbox(warningMessage));
end
  3 Comments
Image Analyst
Image Analyst on 4 Mar 2016
It checks if a file with that filename is there. It does not check what the contents are, or even if there are contents. It's possible to have a file with zero bytes. You can use fileInfo = dir(filename) to check size.

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Azzi Abdelmalek
Azzi Abdelmalek on 29 Sep 2012
Edited: Azzi Abdelmalek on 29 Sep 2012
a=dir % or a=dir('folder')
b=struct2cell(a)
any(ismember(b(1,:),'filename.txt'))
  2 Comments
Jan
Jan on 6 May 2019
But if the current directory contains a huge number of files, it is a waste of time. If the current folder is in a network drive, the slow down is substantial. This is more efficient:
isfile(fullfile(cd, 'filename.txt'))
And if it is unknown, if the file contains a path or not, use https://www.mathworks.com/matlabcentral/fileexchange/28249-getfullpath

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José-Luis
José-Luis on 29 Sep 2012
Edited: José-Luis on 29 Sep 2012
doc exist

Simon
Simon on 2 Nov 2016
Edited: Simon on 2 Nov 2016
A more modern / more succinct approach:
assert( exist( filename, 'file ) == 2, 'File not found.' );
Assert is a wonderful thing, and makes error-catching code a lot more compact than lots of if blocks! The way it works is,
assert( condition, error );
where condition is something that returns a logical true or false, and error is the message that results if it's false.
  2 Comments
Image Analyst
Image Analyst on 17 Nov 2016
Though a friendlier more informative error message (like in my answer) would be an improvement.
But you're not totally correct. Like you said "exist(filename,'file') == 2 would occur when the file DOES exist." and exist(filename,'file') == 2 would be FALSE when the file DOES NOT exist. Since assert only spits out the error message when the file does not exist (the condition is false), it was correct as Simon originally had it, not your "correction".
Remember, in summary, if the file does exist, the condition is true, and the 'File not found.' message is not printed to the command window. If the file does NOT exist, the condition is false, and so the 'File not found.' message is printed to the command window.

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ABHAY K K
ABHAY K K on 4 Feb 2019
is there a way to check the files exists in a particular directory without using the filename, What i mean to say is the more generalised way to find out
  2 Comments
Image Analyst
Image Analyst on 11 Oct 2020
No. If you don't know the filename(s), you cannot determine if a file exists. The best you could do is to see if ANY files exist in the folder by using the dir() function.

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