why matlab shows code while use fprintf

As you found it, this is a simple code to check if the file exsits. But as soon as I execute it, it not only outputs the existed file names but also shows a part of my code, as below.

clear all;
clc;
close all;

for i=1:10 
    for j=1:8
        str1 = num2str(100+i);
        str2 = num2str(i+j-1);
        str = strcat(str1, '_', str2, '.', 'tif');
        if(exist(str,'file')~=0)
            fprintf('%s',str);
        end
    end
end

Result like this:
103_3.tif        str1 = num2str(100+i);
        str2 = num2str(i+j-1);
        str = strcat(str1, '_', str2, '.', 'tif');
        if(exist(str,'file')~=0)
            fprintf('%s',str);
103_4.tif        str1 = num2str(100+i);
        str2 = num2str(i+j-1);
        str = strcat(str1, '_', str2, '.', 'tif');
        if(exist(str,'file')~=0)
        str1 = num2str(100+i);
        str2 = num2str(i+j-1);
        str = strcat(str1, '_', str2, '.', 'tif');
        if(exist(str,'file')~=0)

[David Sanchez]

I tested your code as is and I just had the file name. Obviously there is something wrong with your machine.

[Walter Roberson]

Could you also, for debugging purposes, show length(str) after str is constructed ?