Linux tr命令

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Linux tr 命令用于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，經過字符串轉譯后，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，不符合的剩余部份才進行轉換
• -d, --delete：刪除指令字符
• -s, --squeeze-repeats：縮減連續重復的字符成指定的單個字符
• -t, --truncate-set1：削減 SET1 指定范圍，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

字符集合的范圍：

• \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 水平制表符
• CHAR1-CHAR2 ：字符范圍從 CHAR1 到 CHAR2 的指定，范圍的指定以 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，功能是重復指定的字符到與 SET1 相同長度為止
• [CHAR*REPEAT] ：這也是 SET2 專用的設定，功能是重復指定的字符到設定的 REPEAT 次數為止(REPEAT 的數字采 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:] ：所有控制字符
• [: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(等號里的 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原來的內容  
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 命令大小寫轉換后，得到如下輸出結果：

$ cat testfile | tr a-z A-Z #轉換后的輸出  
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:] #轉換后的輸出  
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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