How to address: Invalid file identifier. Use fopen to generate a valid file identifier?

Question

megha 2023-9-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2025197-how-to-address-invalid-file-identifier-use-fopen-to-generate-a-valid-file-identifier

评论： Walter Roberson 2023-9-25

Hello,

I am trying to run the following lines but it shows error.

fid = fopen('/dev/tty', 'r');
% Display program information
fprintf(fid, '\nDetails of the program.\n');
Error using fprintf
Invalid file identifier. Use fopen to generate a valid file identifier.

I googled answer for it and understood that since fid is -1, I cannot write. But, I do not know how to solve this issue.

Any help is greatly appriciated.

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Answer 1

KALYAN ACHARJYA 2023-9-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2025197-how-to-address-invalid-file-identifier-use-fopen-to-generate-a-valid-file-identifier#answer_1317127

在 MATLAB Online 中打开

fid = fopen('/dev/tty', 'r');  
if fid == -1
    error('Failed to open /dev/tty for writing.');
end
fprintf(fid, 'Details of the program.\n')

#else

% Open for writing (r for reading)
fid = fopen('/dev/tty', 'w');  

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Walter Roberson 2023-9-25

在 MATLAB Online 中打开

device = '/dev/tty';
if ~exist(device, 'file')
    error('no file "%s"', device);
else
    [fid, msg] = fopen(device, 'a+');  
    if fid == -1
        error('Failed to open "%s" because: "%s"', device, msg);
    end
end