How do I open a text file with fopen() in a local function, and return the file identifier to the parent script without MATLAB automatically closing the newly opened file?

I am trying to write my own "wrapper" for fopen(). Just like MATLAB's fopen() I would like to pass it a file name and return a valid file identifier that I can use to interrogate the data in the file. The problem is, if I open a file in my local function myfopen() MATLAB will automatically close it after finishing myfopen()'s execution. Can I instruct MATLAB to leave the file open and accessible to my parent script?

Thanks for any help,

- Guy

[dpb]

MATLAB never automagically closes a file opened with fopen unless somewhere you have either an explicit fclose on that file handle or use fclose('all')

We'd have to see the code outline and a minimum example that illustrates the problem you're seeing to diagnose the issue.

How do you come to the conclusion the file has been closed? More likely I would think is that you simply don't have the file handle in the current scope by having broken the chain of passing it from the initial function that did open the file.

Or, alternatively, do you exhaustively check that the fopen call actually succeeds and the file was ever opened? That would be another highly plausible way in which to (belatedly) discover the variable you're using is not a valid handle.

[Guy Beadie]

Ha!

Thank you for challenging my assumption. You are right: the subfunction did not actually close the file. I made that assumption based on a syntax error in the parent script.

My first test of myfopen() was to pass it a filename, get the file identifier back, and then close the file. This failed, so I assumed I wasn't getting a valid file identifier even though I could tell using the debugger that all was well within myfopen().

My problem? I was "closing" the file with close(fID) ... not fclose(fID). Since close() pertains to figures, not files, I was getting an invalid handle error, which I attributed to the file no longer existing.

Because, of course, I couldn't be doing anything stupid on my end (sigh).

Thank you,

- Guy