uniq命令的作用：顯示唯一的行，對於那些連續重復的行只顯示一次！
接下來通過實踐實例說明：
[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文件的內容，可以看到其中的連續重復行
[root@stu100 ~]# uniq test
boy took bat home
girl took bat home
dog brought hat home
uniq命令不加任何參數，僅顯示連續重復的行一次
[root@stu100 ~]# uniq -c test
2 boy took bat home
1 girl took bat home
3 dog brought hat home
-c 參數顯示文件中每行連續出現的次數。
[root@stu100 ~]# uniq -d test
boy took bat home
dog brought hat home
-d選項僅顯示文件中連續重復出現的行。
[root@stu100 ~]# uniq -u test
girl took bat home
-u選項顯示文件中沒有連續出現的行。
[root@stu100 ~]# uniq -f 2 -s 2 test
boy took bat home
忽略每行的前2個字段，忽略第二個空白字符和第三個字段的首字符，結果at home
[root@stu100 ~]# uniq -f 1 test
boy took bat home
dog brought hat home
忽略每行的第一個字段，這樣boy ，girl開頭的行看起來是連續重復的行。