sprintf format specifiers won't print newline

I'm trying to create a string that has a newline in it. My problem is with sprintf. I'm trying to put a newline (\n) character in my string, and it's behaviour is very strange... sometimes sprintf returns an empty string, and sometimes it just prints '\n' as part of the text. I want it to actually insert a line.

This is sort of what my string looks like, but with some variables inserted between the angle brackets:

 entry = '% * < >\n';

I tried going straight ahead with sprintf:

 sprintf(entry)

This produces

 Empty string: 1-by-0

I tried accounting for the newline:

 sprintf('\n', entry)

This seems to produce just a newline. I then thought maybe the percent sign was special, so I tried the 'escape character' syntax which is mentioned on the sprintf reference page but not really explained:

 sprintf('%%', entry)

This produces just a percent sign. Next I tried using the string specifier %s. I found that

 sprintf('%s', entry)

produced

 % * < >\n

and that

 sprintf('%s\n', entry)

produced the same thing but with a newline after the string, but not where my actually '\n' is. Whenever I add '%%' in there, it just prints out a percent sign. Can anyone tell me what I'm doing wrong? This is puzzling because simply doing sprintf(string) works for me with other strings that have newlines in them.

[Frances]

Do you mean as the format specifier? Because that returns an empty string.

Answer 1

[Frances]

It turns out that '%' needs to be written as '%%' in the string (thank you Honglei Chen), and that was somehow interfering with my newline working as well. In the end I used

 entry = sprintf('%%* < >\n');

which produces

 % * < >

plus a newline. If you use '%s', I guess it interprets every character as itself:

 entry = sprintf('%s', '%%* < >\n');
 ans =
 %%* < >\n

[Image Analyst]

Yes. See my answer. sprintf has the first string argument as the format specifier. Everything after that are your variables that it's going to try to insert into your string according to any specifiers you put in there. specifiers start with the percent symbol. So you did %s and it's going to try to stick your next argument, '%% * < >\n' in place of the %s - that's how sprintf operates. However, as you eventually found out, you can have a string without any variables embedded and with just special characters like \n if you just have one string argument.

Answer 2

[Honglei Chen]

% and \ are escape characters so you need to treat them special, try

sprintf('%%*<>\\n');

You can find this information in the doc

doc sprintf

or

help sprintf

[Frances]

%% works, thanks for that suggestion. However, I'm not trying to insert a backslash into my string, I'm trying to insert a newline character, so using \\ doesn't work. I want the \n to translate as a newline.

[Honglei Chen]

then

sprintf('%%*<>\n')

should work, what's the issue? You can insert it anywhere

sprintf('%%\n*<>')

[Azzi Abdelmalek]

the result is

 %*<>

[Honglei Chen]

There is a new line if you look carefully

Answer 3

[Image Analyst]

It's just a regular sprintf() like you're used to with other languages:

outputString = sprintf('%s\n%d\n%f', myString, myInteger, myDouble);

Simply put in the specifier %s, %d, etc. for the variable you want to insert, then put in \n whenever you want your string to start on a new line. For example:

myString = 'Hello Frances';
myInteger = 42;
myDouble = pi;
outputString = sprintf('%s\n%d%%\n%f', myString, myInteger, myDouble)

In the command window you'll see:

outputString =
Hello Frances
42%
3.141593

Note, each is on a new line.