Linux命令uniq的作用是过滤重复部分显示文件内容，这个命令读取输入文件，并比较相邻的行。在正常情况下，第二个及以后更多个重复行将被删去，行比较是根据所用字符集的排序序列进行的。该命令加工后的结果写到输出文件中。输入文件和输出文件必须不同。如果输入文件用“- ”表示，则从标准输入读取。
uniq [选项] 文件
说明：这个命令读取输入文件，并比较相邻的行。在正常情况下，第二个及以后更多个重复行将被删去，行比较是根据所用字符集的排序序列进行的。该命令加工后的结果写到输出文件中。输入文件和输出文件必须不同。如果输入文件用“- ”表示，则从标准输入读取。
该命令各选项含义如下：、
– c 显示输出中，在每行行首加上本行在文件中出现的次数。它可取代- u和- d选项。
– d 只显示重复行。
– u 只显示文件中不重复的各行。
– n 前n个字段与每个字段前的空白一起被忽略。一个字段是一个非空格、非制表符的字符串，彼此由制表符和空格隔开(字段从0开始编号)。
+n 前n个字符被忽略，之前的字符被跳过(字符从0开始编号)。
– f n 与- n相同，这里n是字段数。
– s n 与+n相同，这里n是字符数。
接下来通过实践实例说明：
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[root@stu100 ~]#cat test
boy took bathome
boy took bathome
girl took bathome
boy took bathome
boy took bathome
dog brought hathome
dog brought hathome
dog brought hathome
看test文件的内容
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[root@stu100 ~]#uniq test
boy took bathome
girl took bathome
boy took bathome
dog brought hathome
uniq命令不加任何参数，仅显示连续重复的行一次
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[root@stu100 ~]# uniq -c test
2 boy took bathome
1 girl took bathome
2 boy took bathome
3 dog broughthat home
1
-c 参数显示文件中每行连续出现的次数。
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[root@stu100 ~]#cat test |sort | uniq -c
1
4 boy took bathome
3 dog broughthat home
1 girl took bathome
排序后再显示
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[root@stu100 ~]#uniq -d test
boy took bathome
boy took bathome
dog brought hathome
-d选项仅显示文件中连续重复出现的行。
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[root@stu100 ~]#uniq -u test
girl took bathome
-u选项显示文件中没有连续出现的行。
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[root@stu100 ~]#uniq -f 2 -s 2 test
boy took bathome
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，结果at home
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[root@stu100 ~]#uniq -f 1 test
boy took bathome
dog brought hathome
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。
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[root@stu100 ~]#uniq -D test
boy took bathome
boy took bathome
boy took bathome
boy took bathome
dog brought hathome
dog brought hathome
dog brought hathome
显示所有重复的行，每个重复的行都显示
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