Passing formatted string output of sprintf to fprintf

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Louis 2020-5-11

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评论： Louis 2020-5-13

I have a writeToLog function which takes formatted string and uses fprintf to print the formated string to both a log file and to a command window.

When I use fprintf to print a file location by passing file directory directly, it works perfectly:

dir = '\\file_server\parent_dir\sub_dir';
fprintf('Saving the log file to: %s\n', dir))

However, when I pass the formated string output of sprintf to fprintf, it errors out:

format_str = sprintf('Saving the log file to: %s\n', dir)
>> fprintf(format_str)
Warning: Escaped character '\p' is not valid. See 'doc sprintf' for supported special characters. 
Saving the log file to: \file_server>> 

Is there a way for fprintf to print the formatted string as is?

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Hank 2020-5-11

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Since the string is already formatted, just use

disp(formated_str)

Louis 2020-5-11

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Thanks for the suggestions.

I have a helper function

function writeToLog(fid, formatted_str)
    % print to log file
    fprintf(fid, formatted_str);
    % print to command window
    fprintf(formatted_str);
end

And the purpose of this function is to write information to both the command window and a log file.

Since I wanted to keep this function just take the file id and the formatted string, every where in my code I have

formatted_str = sprintf(...);
writeToLog(fid, formatted_str);

Not sure display alone will help me to write to both the command window and the log file.

Any suggestions?

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Answer 1

Image Analyst 2020-5-11

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You'll need to do

function writeToLog(fid, formatted_str)
    % Write to log file.
    fprintf(fid, '%s\n', formatted_str);
    % Print to command window.
    fprintf('%s\n', formatted_str);
end

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Louis 2020-5-13

Thank you!

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Answer 2

Steven Lord 2020-5-11

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format_str = sprintf('Saving the log file to: %s\n', dir)
>> fprintf('%s', format_str)

You don't want to use the string created by sprintf as the format specifier, you want to use it as data with the '%s' format specifier.

BTW, you may want to use a different variable name to contain the name of your directory. dir already has a meaning in MATLAB.

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Steven Lord 2020-5-13

If the second input to writeToLog has always passed through sprintf, it's always going to be text (either a char or string array.) So tell fprintf that just like Image Analyst suggested.

Louis 2020-5-13