# Linux tr命令 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. ```