一，uniq干什么用的
文本中的重復(fù)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(fù)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(jìn)行組合使用，因為uniq 不會檢查重復(fù)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)，然后非空字符，域中字符前的空字符將被跳過
二，uniq參數(shù)說明
[zhangy@BlackGhost ~]$ uniq --help
用法：uniq [選項]... [文件]
從輸入文件或者標(biāo)準(zhǔn)輸入中篩選相鄰的匹配行并寫入到輸出文件或標(biāo)準(zhǔn)輸出。/p>
p>不附加任何選項時匹配行將在首次出現(xiàn)處被合并。/p>
p>長選項必須使用的參數(shù)對于短選項時也是必需使用的。
-c, --count //在每行前加上表示相應(yīng)行目出現(xiàn)次數(shù)的前綴編號
-d, --repeated //只輸出重復(fù)的行
-D, --all-repeated //只輸出重復(fù)的行，不過有幾行輸出幾行
-f, --skip-fields=N //-f 忽略的段數(shù)，-f 1 忽略第一段
-i, --ignore-case //不區(qū)分大小寫
-s, --skip-chars=N //根-f有點像，不過-s是忽略，后面多少個字符 -s 5就忽略后面5個字符
-u, --unique //去除重復(fù)的后，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 個字符以后的內(nèi)容不作對照
--help //顯示此幫助信息并退出
--version //顯示版本信息并退出
其中-z不知道有什么用
三，測試文本文件uniqtest
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
[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(fù)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(fù)行的時候，只會檢查相鄰的行。重復(fù)數(shù)據(jù)，肯定有很多不是相鄰在一起的。
[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
[zhangy@BlackGhost mytest]$ uniq -d -c uniqtest
3 this is a test
2 i love tank
uniq -d 只顯示重復(fù)的行
[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(fù)的行，并且把重復(fù)幾行都顯示出來。他不能和-c一起使用
[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
在這里those只有一行，顯示的卻是重復(fù)了，這是因為，-f 1 忽略了第一列，檢查重復(fù)從第二字段開始的。
[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(qū)分大小寫
[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 //根上一個例子有什么不同
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。
[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(fù)的項，然后全部顯示出來
[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個字符以后的內(nèi)容不作檢查，所以i am tank 根 i love tank就一樣了。
