strtok and while loop

Hello I'm new in Matlab I need to write a program that makes the user to input a sentence and then prints each word on a separate line after converting its characters to uppercase using while loop and strtok function. How could I do that? I wrote this but still I got an error.

f=input('Enter a sentence: ');
a=[];
while length(f)~=0
    [f, r] = strtok(f);
    a=[a upper(f) 10];
    f=r;
end
disp(a);

[Geoff Hayes]

What have you tried so far? Have you looked at the documentation to see how you might request an input string from the user? What does the documentation say on using while or strtok?

[Walter Roberson]

f=input('Enter a sentence: ', 's');