MATLAB: Change a bunch of files name

Question

I have a set of images in image folder located at C:\temp\image. The images are from yale faces, and I want to add extension .jpg to file name(like that subject01.glasses.jpg, subject01.happy.jpg). The original names are like that subject01.glasses, subject01.happy.

I got the error message "Cannot open file "." for reading. You might not have read permission. "

    clc;clear all;close all;
    f=dir('*');
    fil={f.name};  
    for k=1:numel(fil)
        file=fil{k};
        new_file = sprintf('%sjpg',file);;
        %  % new_file=strrep(file,'.jpg','.png')
        im=imread(file);
        imwrite(im,new_file);
    end

Answer 1

Before

fil={f.name};

do

f([f.isdir]) = [];