uniq命令的作用：显示唯一的行，对于那些连续重复的行只显示一次！
接下来通过实践实例说明：
[root@stu100 ~]# cat test boy took bat home boy took bat home girl took bat home dog brought hat home dog brought hat home dog brought hat home
看test文件的内容，可以看到其中的连续重复行
[root@stu100 ~]# uniq test boy took bat home girl took bat home dog brought hat home
uniq命令不加任何参数，仅显示连续重复的行一次
[root@stu100 ~]# uniq -c test 2 boy took bat home 1 girl took bat home 3 dog brought hat home
-c 参数显示文件中每行连续出现的次数。
[root@stu100 ~]# uniq -d test boy took bat home dog brought hat home
-d选项仅显示文件中连续重复出现的行。
[root@stu100 ~]# uniq -u test girl took bat home
-u选项显示文件中没有连续出现的行（去除重复）。
[root@stu100 ~]# uniq -f 2 -s 2 test boy took bat home
-f（跳过的字段）和-s（跳过的字符数）选项忽略每行的前2个字段，忽略第二个空白字符和第三个字段的首字符（从跳过的字段数开始算起，与-f选项配合使用），结果at home
[root@stu100 ~]# uniq -f 1 test boy took bat home dog brought hat home
-f选项忽略每行的第一个字段，这样boy ，girl开头的行看起来是连续重复的行。
lxy@lxy-e440:~$ uniq -w 3 test.txt boy took bat home girl took bat home dog brought hat home lxy@lxy-e440:~$ uniq -w 3 -u test.txt girl took bat home lxy@lxy-e440:~$ uniq -w 3 -d test.txt boy took bat home dog brought hat home
-w选项对每行第N 个字符以后的内容不作对照