一，uniq干什麼用的
文本中的重復行，基本上不是我們所要的，所以就要去除掉。linux下有其他命令可以去除重復行，但是我覺得uniq還是比較方便的一個。使用uniq的時候要注意以下二點
1，對文本操作時，它一般會和sort命令進行組合使用，因為uniq 不會檢查重復的行，除非它們是相鄰的行。如果您想先對輸入排序，使用sort -u。
2，對文本操作時，若域中為先空字符(通常包括空格以及制表符)，然後非空字符，域中字符前的空字符將被跳過
二，uniq參數說明
代碼如下:
[zhangy@BlackGhost ~]$ uniq --help
用法：uniq [選項]... [文件]
從輸入文件或者標准輸入中篩選相鄰的匹配行並寫入到輸出文件或標准輸出。</p>
<p>不附加任何選項時匹配行將在首次出現處被合並。</p>
<p>長選項必須使用的參數對於短選項時也是必需使用的。
-c, --count //在每行前加上表示相應行目出現次數的前綴編號
-d, --repeated //只輸出重復的行
-D, --all-repeated //只輸出重復的行，不過有幾行輸出幾行
-f, --skip-fields=N //-f 忽略的段數，-f 1 忽略第一段
-i, --ignore-case //不區分大小寫
-s, --skip-chars=N //根-f有點像，不過-s是忽略，後面多少個字符 -s 5就忽略後面5個字符
-u, --unique //去除重復的後，全部顯示出來，根mysql的distinct功能上有點像
-z, --zero-terminated end lines with 0 byte, not newline
-w, --check-chars=N //對每行第N 個字符以後的內容不作對照
--help //顯示此幫助信息並退出
--version //顯示版本信息並退出
其中-z不知道有什麼用
三，測試文本文件uniqtest
代碼如下:
this is a test
this is a test
this is a test
i am tank
i love tank
i love tank
this is a test
whom have a try
WhoM have a try
you have a try
i want to abroad
those are good men
we are good men
四，實例詳解
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -c uniqtest
3 this is a test
1 i am tank
2 i love tank
1 this is a test //和第一行是重復的
1 whom have a try
1 WhoM have a try
1 you have a try
1 i want to abroad
1 those are good men
1 we are good men
從上例子中我們可以看出，uniq的一個特性，檢查重復行的時候，只會檢查相鄰的行。重復數據，肯定有很多不是相鄰在一起的。
代碼如下:
[zhangy@BlackGhost mytest]$ sort uniqtest |uniq -c
1 WhoM have a try
1 i am tank
2 i love tank
1 i want to abroad
4 this is a test
1 those are good men
1 we are good men
1 whom have a try
1 you have a try
這樣就可以解決上個例子中提到的問題
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -d -c uniqtest
3 this is a test
2 i love tank
uniq -d 只顯示重復的行
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -D uniqtest
this is a test
this is a test
this is a test
i love tank
i love tank
uniq -D 只顯示重復的行，並且把重復幾行都顯示出來。他不能和-c一起使用
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -f 1 -c uniqtest
3 this is a test
1 i am tank
2 i love tank
1 this is a test
2 whom have a try
1 you have a try
1 i want to abroad
2 those are good men //只有一行，顯示二行
在這裡those只有一行，顯示的卻是重復了，這是因為，-f 1 忽略了第一列，檢查重復從第二字段開始的。
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -i -c uniqtest
3 this is a test
1 i am tank
2 i love tank
1 this is a test
2 whom have a try //一個大寫，一個小寫
1 you have a try
1 i want to abroad
1 those are good men
1 we are good men
檢查的時候，不區分大小寫
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -s 4 -c uniqtest
3 this is a test
1 i am tank
2 i love tank
1 this is a test
3 whom have a try //根上一個例子有什麼不同
1 i want to abroad
1 those are good men
1 we are good men
檢查的時候，不考慮前4個字符，這樣whom have a try 就和 you have a try 就一樣了。
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -u uniqtest
i am tank
this is a test
whom have a try
WhoM have a try
you have a try
i want to abroad
those are good men
we are good men
去重復的項，然後全部顯示出來
代碼如下:
[zhangy@BlackGhost mytest]$ uniq -w 2 -c uniqtest
3 this is a test
3 i am tank
1 this is a test
1 whom have a try
1 WhoM have a try
1 you have a try
1 i want to abroad
1 those are good men
1 we are good men
對每行第2個字符以後的內容不作檢查，所以i am tank 根 i love tank就一樣了。