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how can we check file existence?

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Safiullah Khan
Safiullah Khan 2011-4-12
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.

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采纳的回答

Walter Roberson
Walter Roberson 2011-4-12
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 个评论
Jan
Jan 2011-4-12
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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更多回答（2 个）

Safiullah Khan
Safiullah Khan 2011-4-12
thank you so much Walter Roberson for your reply. it did worked for me.
Yahia chs
Yahia chs 2011-5-20
thank you very much this was really felpful!!!!!!!

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