how can we check file existence?

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.

Answer 1

[Walter Roberson]

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.

[Jan]

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.

Answer 2

[Safiullah Khan]

thank you so much Walter Roberson for your reply. it did worked for me.

Answer 3

[Yahia chs]

thank you very much this was really felpful!!!!!!!