fclose() doesnt work

hi, I doing a very simple script to read data from a .txt file. Here is the only code in my script so far :

clc;
clear;
fid = fopen('fd.txt','r');
data = fscanf(fid,'%f');
fclose(fid);

But then, if I want to delete or change the name file it wont let me, it tell me the file is still open in matlab. Is it a bug or am I doing something wrong?

[Adam]

Works fine when I try it with a newly created file. What is the output of fclose if you just put

fclose( fid )

without the semi-colon?

I have had occasions in the past though where Matlab seems to hold onto file handles after I had called fclose and I ended up doing an

fclose( 'all' )

which is not ideal.

Answer 1

[dpb]

Probably in your testing you have had an error or other misstep along the way in which you have overwritten the file handle variable fid for the file while it was still open and so the fclose operation is not operating on the correct fid.

You're not testing the return of fopen so you don't know that it has succeeded or you may have multiple connections to the same file open simultaneously.

As Adam notes, use fclose('all') to get back to ground zero and all will be well again. And, add the error-checking... :)

ADDENDUM

There are some other useful options in fopen for diagnosing such problems as well...

help fopen
  ...
fIDs = fopen('all') returns a row vector containing the file identifiers of 
all open files.  The identifiers reserved for standard input, output, and 
error are not included.  The number of elements in the vector is equal to 
the number of open files.

filename = fopen(fileID) returns the file name that a previous call to 
fopen used when it opened the file specified by fileID.  The output  
filename is resolved to the full path. The fopen function does not read 
information from the file to determine the output value.
...