Error using fprintf Invalid file identifier. Use fopen to generate a valid file identifier.

Hello, I tried using fprint in different programms also examples, nothing worked.

Wath can i do if my fileID is -1 and using the full path does not work either.

this are my fileattributes

archive: 0

system: 0

hidden: 0

directory: 1

UserRead: 1

UserWrite: 1

UserExecute: 1

GroupRead: NaN

GroupWrite: NaN

GroupExecute: NaN

OtherRead: NaN

OtherWrite: NaN

OtherExecute: NaN

I dont know wath to do, please help ?

Answer 1

[Walter Roberson]

       directory: 1

That tells us that you have named a folder (directory) rather than a file or device name.

      GroupRead: NaN

That tells us that you are using MS WIndows rather than MacOS or Linux.

On MS Windows, it is not permitted to fopen() a directory.

(It is not permitted on MacOS either, but historically it used to be possible on old versions of Unix; you would get out the internal binary representation of the directory.)

You will need to change your path so that you are naming a file rather than a directory.

[Lorenz Untersulzner]

Ok,I tried this path

fileID = fopen('C:\Users\Ollol\Desktop\Protocol.txt', 'wt');

but does not work

Protocol.txt is a filename or not?

[Walter Roberson]

Experiment with

filename = 'C:\Users\Ollol\Desktop\Protocol.txt';
[fileID, message] = fopen(filename, 'wt');
if fileID < 0
    error('Failed to open file "%s" because "%s"', filename, message)
end

[Lorenz Untersulzner]

It worked if i dont specify the file (.txt)

thanks very much !

[Walter Roberson]

What was the message that was produced?

I suspect you have an existing Protocol.txt that you cannot write to.