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每天学一个 Linux 命令（33）：uniq
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命令简介
uniq 命令用于去除文件中重复行，一般与 sort 命令结合使用。
语法格式
uniq [选项] [标准输入 [输出]]
uniq [OPTION] [INPUT [OUTPUT]]
输入文件 #指定要去除的重复行文件。如果不指定该项，则从标准读入
输出文件 #指定要去除重复行后的内容要写入的输出文件。如果不指定此项，则将内容显示到标准输出设备（显示终端）。
选项说明
-c #在每列旁边显示该行重复出现的次数
-d #只显示重复出现的行与列
-f #忽略比较指定的字段
-s #忽略比较指定的字符
-i #不区分大小写的比较
-u #只显示出现过一次的行与列
-w #指定要比较的字符
-z #用0字节（NULL）代替换行符
--help #显示帮助信息并退出
--version #显示版本信息并退出
应用举例
#删除重复行
[root@centos7 ~]# cat test.txt
This is a test line
This is a test line
This is a test line
This is also a test line
This is also a test line
This is also also a test line
[root@centos7 ~]# uniq test.txt
This is a test line
This is also a test line
This is also also a test line
[root@centos7 ~]# sort test.txt | uniq
This is also also a test line
This is also a test line
This is a test line
#只显示单一行
[root@centos7 ~]# uniq -u test.txt
This is also also a test line
[root@centos7 ~]# sort test.txt |uniq -u
This is also also a test line
#统计各行在文件中出现的次数
[root@centos7 ~]# sort test.txt |uniq -c
1 This is also also a test line
2 This is also a test line
3 This is a test line
#在文件中找出重复的行
[root@centos7 ~]# sort test.txt |uniq -d
This is also a test line
This is a test line
每天学一个 Linux 命令（31）：md5sum