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how can we check file existence?

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hi, i am writing my application(gui app) data to a text file (appdata.txt) and i want to make sure that every time when the application runs it doesn't create a new file or a copy of a file, the problem is:
1) how can i check if the appdata.txt already exists or not (if not then create new text file or else append data to existing one)
thanks for any help.

Accepted Answer

Walter Roberson
Walter Roberson on 12 Apr 2011
if exist('appdata.txt', 'file')
However, the bit about appending suggests that all you really need to do is,
fid = fopen('appdata.txt', 'at');
This will create a new file if needed and append to an existing file if it is there.
  1 Comment
Jan
Jan on 12 Apr 2011
EXIST(Name, 'file') replies a non-zero number for directories also:
if exist(tempdir, 'file'), disp('found'); end
A better check is:
if exist(Name, 'file') && ~exist(Name, 'dir')
or:
if exist(Name, 'file') == 2
I prefer "fopen(Name, 'r+')", because the append mode needs to locate the end of the file at first, which is time-consuming for large files.

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More Answers (2)

Safiullah Khan
Safiullah Khan on 12 Apr 2011
thank you so much Walter Roberson for your reply. it did worked for me.

Yahia chs
Yahia chs on 20 May 2011
thank you very much this was really felpful!!!!!!!

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