MATLAB Programming

Using Low-Level File I/O Functions
If fopen fails, for example if you try to open a file that does not exist, fopen
• Assigns -1 to the file identifier.
• Assigns an error message to an optional second output argument. Note
that the error messages are system dependent and are not provided for all
errors on all systems. The function ferror can also provide information
about errors.
Test the file identifier each time you open a file in your code. For example,
this code loops until a readable filename is entered:
fid=0;
while fid < 1
filename=input('Open file: ', 's');
[fid,message] = fopen(filename, 'r');
if fid == -1
disp(message)
end
end
When you run this code, if you specify a file that doesn’t exist, such as
nofile.mat, attheOpen file: prompt, the results are
Open file: nofile.mat
Sorry. No help in figuring out the problem . . .
If you specify a file that does exist, such as goodfile.mat, the code example
returns the file identifier, fid, and exits the loop.
Open file: goodfile.mat
Opening Temporary Files and Directories
The tempdir and tempname functions assist in locating temporary data on
your system.
Function
tempdir
tempname
Purpose
Get temporary directory name.
Get temporary filename.
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