Input of linebreak into sprintf?

Question

Andreas Dorner 2019-5-6

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https://ww2.mathworks.cn/matlabcentral/answers/460456-input-of-linebreak-into-sprintf

评论： Steven Lord 2019-5-6

采纳的回答： Jan

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Hello,

i want to input a linebreak ( via '\n' ) into a string. I mean something like this:

a =sprintf('A%sA', '\n');
%this produces
a =
A\nA
%but i want it to produce
a =
A
A

How would I do that?

/edit: this is a minimal example just to show my point, of course. The case i want to work with has multiple inputs and a more complex formatSpec..

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Answer 1

Jan 2019-5-6

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https://ww2.mathworks.cn/matlabcentral/answers/460456-input-of-linebreak-into-sprintf#answer_373753

编辑：Jan 2019-5-6

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a = sprintf('A\nA')
% Or
a = sprintf('A%cA', char(10))    % %s would work also
% Use |newline| instead of char(10) in modern Matlab versions

Your code is the correct method to insert tha characters '\n' directly:

a = sprintf('A%sA', '\n');
% Equivalent to:
a = sprintf('A\\nA');

This is useful, if a file name is printed with path, because this is not reliable:

sprintf(['File: ', filename, '\n'])

If filename contains a control character as \n, \t, \c or e.g. a %s, the output will be confusing. The same must be considered for warnings and errors:

error(['Failing: ', filename])

A clean way without danger of confusing output:

error('Failing: %s', filename)

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Jan 2019-5-6

编辑：Jan 2019-5-6

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@Andreas: The rules are:

In the format specifier of sprintf and fprintf the \ means, that the following character is treated as control. Examples: \n \r \t \a \b \10
To include a \ as character in a format specifier, use \\
Anywhere else in a string or char vector, a \ is simply \

So to include a line break (which is CHAR(10)), either include \n in the format specifier, or a char(10) in the string or char vector. So these commands produce the same results:

a = char(10)
b = sprintf('\n')
isequal(a,b)  % Yes!
a = ['Line1', char(10), 'Line2']
b = sprintf('Line1\nLine2')
c = sprintf('%s\n%s', 'Line1', 'Line2')
d = sprintf('%s%c%s', 'Line1', char(10), 'Line2')
isequal(a, b, c, d)  % Yes

Clear now?

Steven Lord 2019-5-6

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I want to increase the visiblity of one suggestion Jan made earlier in a comment in the original answer. if you're using release R2016b or later, I recommend using newline instead of char(10). IMO this makes the code author's intent very clear and avoids "magic numbers".

A = ['Line 1', newline, 'Line 2']

Note however that A is still a row vector even though it is displayed like it had two rows.