$ls<enter>
a_file	b_file	c_file	x_dir	y_dir
$ls -l<enter>
total 3
-rw-rw-rw-    1 Masahiro nashi           23 Jul 22 03:06 a_file
-rw-rw-rw-    1 Masahiro nashi           23 Jul 22 03:06 b_file
-rw-rw-rw-    1 Masahiro nashi           23 Jul 22 03:06 c_file
drwxrwxrwx    2 Masahiro nashi            0 Jul 22 03:07 x_dir
drwxrwxrwx    2 Masahiro nashi            0 Jul 22 03:07 y_dir
$ls -a<enter>
.	..	a_file	b_file	c_file	x_dir	y_dir
$ls -p<enter>
a_file	b_file	c_file	x_dir/	y_dir/
$ls -r<enter>
y_dir	x_dir	c_file	b_file	a_file
$ls -s<enter>
total 3
1 a_file1    b_file    1 c_file    0 x_dir    0 y_dir
$ls -R<enter>
.:
a_file	b_file	c_file	x_dir	y_dir

./x_dir:
d_file  e_file

./y_dir:
f_file