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Linux tr命令

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Linux tr 命令用於轉換或刪除文件中的字符。

tr 指令從標準輸入設備讀取數據，經過字符串轉譯後，將結果輸出到標準輸出設備。

語法 

tr [-cdst][--help][--version][第一字符集][第二字符集]  
tr [OPTION]…SET1[SET2]

參數說明：

  • -c, --complement：反選設定字符。 也就是符合SET1 的部份不做處理，不符合的剩餘部份才進行轉換
  • -d, --delete：刪除指令字符
  • -s, --squeeze-repeats：縮減連續重複的字符成指定的單個字符
  • -t, --truncate-set1：削減SET1 指定範圍，使之與SET2 設定長度相等
  • --help：顯示程序用法信息
  • --version：顯示程序本身的版本信息

字符集合的範圍：

  • \NNN 八進制值的字符NNN (1 to 3 為八進制值的字符)
  • \\ 反斜杠
  • \a Ctrl-G 鈴聲
  • \b Ctrl-H 退格符
  • \f Ctrl-L 走行換頁
  • \n Ctrl-J 新行
  • \r Ctrl-M 回車
  • \t Ctrl-I tab鍵
  • \v Ctrl-X 水平製表符
  • CHAR1-CHAR2 ：字符範圍從CHAR1 到CHAR2 的指定，範圍的指定以ASCII 碼的次序為基礎，只能由小到大，不能由大到小。
  • [CHAR*] ：這是SET2 專用的設定，功能是重複指定的字符到與SET1 相同長度為止
  • [CHAR*REPEAT] ：這也是SET2 專用的設定，功能是重複指定的字符到設定的REPEAT 次數為止(REPEAT 的數字採8 進位制計算，以0 為開始)
  • [:alnum:] ：所有字母字符與數字
  • [:alpha:] ：所有字母字符
  • [:blank:] ：所有水平空格
  • [:cntrl:] ：所有控製字符
  • [:digit:] ：所有數字
  • [:graph:] ：所有可打印的字符(不包含空格符)
  • [:lower:] ：所有小寫字母
  • [:print:] ：所有可打印的字符(包含空格符)
  • [:punct:] ：所有標點字符
  • [:space:] ：所有水平與垂直空格符
  • [:upper:] ：所有大寫字母
  • [:xdigit:] ：所有16 進位制的數字
  • [=CHAR=] ：所有符合指定的字符(等號裡的CHAR，代表你可自訂的字符)

實例

將文件testfile中的小寫字母全部轉換成大寫字母，此時，可使用如下命令： 

cat testfile |tr a-z A-Z

testfile文件中的內容如下： 

$ cat testfile         #testfile原来的内容  
Linux networks are becoming more and more common, 
but scurity is often an overlooked  
issue. Unfortunately, in today’s environment all networks 
are potential hacker targets,  
fro0m tp-secret military research networks to small home LANs.  
Linux Network Securty focuses on securing Linux in a 
networked environment, where the  
security of the entire network needs to be considered
rather than just isolated machines.  
It uses a mix of theory and practicl techniques to 
teach administrators how to install and  
use security applications, as well as how the 
applcations work and why they are necesary.

使用tr 命令大小寫轉換後，得到如下輸出結果： 

$ cat testfile | tr a-z A-Z #转换后的输出  
LINUX NETWORKS ARE BECOMING MORE AND MORE COMMON, BUT SCURITY IS OFTEN AN OVERLOOKED  
ISSUE. UNFORTUNATELY, IN TODAY’S ENVIRONMENT ALL NETWORKS ARE POTENTIAL HACKER TARGETS,  
FROM TP-SECRET MILITARY RESEARCH NETWORKS TO SMALL HOME LANS.  
LINUX NETWORK SECURTY FOCUSES ON SECURING LINUX IN A NETWORKED ENVIRONMENT, WHERE THE  
SECURITY OF THE ENTIRE NETWORK NEEDS TO BE CONSIDERED RATHER THAN JUST ISOLATED MACHINES.  
IT USES A MIX OF THEORY AND PRACTICL TECHNIQUES TO TEACH ADMINISTRATORS HOW TO INSTALL AND  
USE SECURITY APPLICATIONS, AS WELL AS HOW THE APPLCATIONS WORK AND WHY THEY ARE NECESARY.

大小寫轉換，也可以通過[:lower][:upper]參數來實現。 例如使用如下命令： 

cat testfile |tr [:lower:] [:upper:]

輸出結果如下： 

$ cat testfile | tr [:lower:] [:upper:] #转换后的输出  
LINUX NETWORKS ARE BECOMING MORE AND MORE COMMON, BUT SCURITY IS OFTEN AN OVERLOOKED  
ISSUE. UNFORTUNATELY, IN TODAY’S ENVIRONMENT ALL NETWORKS ARE POTENTIAL HACKER TARGETS,  
FROM TP-SECRET MILITARY RESEARCH NETWORKS TO SMALL HOME LANS.  
LINUX NETWORK SECURTY FOCUSES ON SECURING LINUX IN A NETWORKED ENVIRONMENT, WHERE THE  
SECURITY OF THE ENTIRE NETWORK NEEDS TO BE CONSIDERED RATHER THAN JUST ISOLATED MACHINES.  
IT USES A MIX OF THEORY AND PRACTICL TECHNIQUES TO TEACH ADMINISTRATORS HOW TO INSTALL AND  
USE SECURITY APPLICATIONS, AS WELL AS HOW THE APPLCATIONS WORK AND WHY THEY ARE NECESARY.

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