ls是list files and directories的缩写，即列出目录中的文件和子目录。
ls命令最简单的用法就是不加任何参数，执行后会列出当前目录下所有目录和文件的名称。
# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
ls可以添加参数以显示更多的内容：
显示内容包括隐藏文件、.（表示当前目录）和..（表示上一层目录）：
# ls -a
. .. bin boot dev etc home lib lib64 media mnt opt proc .readahead root run sbin srv sys tmp usr var
显示内容包括隐藏文件，但是不包括.（表示当前目录）和..（表示上一层目录）：
# ls -A
bin boot dev etc home lib lib64 media mnt opt proc .readahead root run sbin srv sys tmp usr var
显示文件和目录的详细信息：
# ls -l
total 36
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 bin -> usr/bin
dr-xr-xr-x. 4 root root 4096 Sep 15 19:35 boot
drwxr-xr-x. 19 root root 3020 Sep 21 21:59 dev
drwxr-xr-x. 102 root root 8192 Sep 21 21:59 etc
drwxr-xr-x. 3 root root 17 Sep 15 19:35 home
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Sep 15 19:26 lib64 -> usr/lib64
drwxr-xr-x. 2 root root 6 Aug 12 2015 media
drwxr-xr-x. 2 root root 6 Aug 12 2015 mnt
drwxr-xr-x. 3 root root 15 Sep 15 19:32 opt
dr-xr-xr-x. 149 root root 0 Sep 21 21:59 proc
dr-xr-x---+ 14 root root 4096 Sep 20 11:46 root
drwxr-xr-x. 30 root root 960 Sep 21 22:00 run
lrwxrwxrwx. 1 root root 8 Sep 15 19:26 sbin -> usr/sbin
drwxr-xr-x. 2 root root 6 Aug 12 2015 srv
dr-xr-xr-x. 13 root root 0 Sep 21 21:59 sys
drwxrwxrwt. 9 root root 4096 Sep 21 21:59 tmp
drwxr-xr-x. 13 root root 4096 Sep 15 19:26 usr
drwxr-xr-x. 21 root root 4096 Sep 21 21:59 var
可以按修改的日期时间进行排序（由近到远）输出：
# ls -tl
total 36
drwxr-xr-x. 30 root root 960 Sep 21 22:00 run
drwxrwxrwt. 9 root root 4096 Sep 21 21:59 tmp
drwxr-xr-x. 102 root root 8192 Sep 21 21:59 etc
drwxr-xr-x. 19 root root 3020 Sep 21 21:59 dev
dr-xr-xr-x. 13 root root 0 Sep 21 21:59 sys
drwxr-xr-x. 21 root root 4096 Sep 21 21:59 var
dr-xr-xr-x. 149 root root 0 Sep 21 21:59 proc
dr-xr-x---+ 14 root root 4096 Sep 20 11:46 root
dr-xr-xr-x. 4 root root 4096 Sep 15 19:35 boot
drwxr-xr-x. 3 root root 17 Sep 15 19:35 home
drwxr-xr-x. 3 root root 15 Sep 15 19:32 opt
drwxr-xr-x. 13 root root 4096 Sep 15 19:26 usr
lrwxrwxrwx. 1 root root 8 Sep 15 19:26 sbin -> usr/sbin
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Sep 15 19:26 lib64 -> usr/lib64
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 bin -> usr/bin
drwxr-xr-x. 2 root root 6 Aug 12 2015 media
drwxr-xr-x. 2 root root 6 Aug 12 2015 mnt
drwxr-xr-x. 2 root root 6 Aug 12 2015 srv
可以按修改的日期时间进行排序（由远到近）输出：
[root@localhost /]# ls -rtl
total 36
drwxr-xr-x. 2 root root 6 Aug 12 2015 srv
drwxr-xr-x. 2 root root 6 Aug 12 2015 mnt
drwxr-xr-x. 2 root root 6 Aug 12 2015 media
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 bin -> usr/bin
lrwxrwxrwx. 1 root root 9 Sep 15 19:26 lib64 -> usr/lib64
lrwxrwxrwx. 1 root root 7 Sep 15 19:26 lib -> usr/lib
lrwxrwxrwx. 1 root root 8 Sep 15 19:26 sbin -> usr/sbin
drwxr-xr-x. 13 root root 4096 Sep 15 19:26 usr
drwxr-xr-x. 3 root root 15 Sep 15 19:32 opt
drwxr-xr-x. 3 root root 17 Sep 15 19:35 home
dr-xr-xr-x. 4 root root 4096 Sep 15 19:35 boot
dr-xr-x---+ 14 root root 4096 Sep 20 11:46 root
dr-xr-xr-x. 149 root root 0 Sep 21 21:59 proc
drwxr-xr-x. 21 root root 4096 Sep 21 21:59 var
dr-xr-xr-x. 13 root root 0 Sep 21 21:59 sys
drwxr-xr-x. 19 root root 3020 Sep 21 21:59 dev
drwxr-xr-x. 102 root root 8192 Sep 21 21:59 etc
drwxrwxrwt. 9 root root 4096 Sep 21 21:59 tmp
drwxr-xr-x. 30 root root 960 Sep 21 22:00 run
除了可以显示当前目录外，也可以显示指定目录的内容。
显示指定目录/var的内容：
# ls /var
account adm cache crash db empty games gopher kerberos lib local lock log mail nis opt preserve run spool tmp www yp