Input of linebreak into sprintf?

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..

Answer 1

[Jan]

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)

[Stephen23]

Also worth considering:

a = sprintf('A%cA',sprintf('\n'))

[Andreas Dorner]

But something like that would not be possible:

inputBlock = 'the First Line\nthe Second Line\nAnd The Third for good measure';
sprintf('this is some large formatSpec\nAnd there comes my block:\n\n%s\n\nThis is after the block', inputBlock)

[Stephen23]

"But something like that would not be possible:"

Correct. But you can easily do this:

inputBlock = sprintf('the First Line\nthe Second Line\nAnd The Third for good measure');
...

With the exception of the apostrophe, in MATLAB all characters are interpreted literally in character vector definitions. You can use escaped characters in the format string of sprintf or fprintf or error (note that it is the function itself that interprets the escaped characters, the escaped characters are still literally present in the format string itself).

[Jan]

@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]

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.

>> isrow(A)
ans =
  logical
   1