Linux 命令- tr

        tr 命令用户转换或删除文件中的字符。

        tr 指令从标准输入设备读取数据，经过字符串转以后，将结果输出到标准输出设备。

1. 命令语法

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tr [参数] [第一字符集] [第二字符集]
tr [OPTION] [SET1] [SET2]

2. 命令参数

  • -c, –complement：反选设定字符。也就是符合 SET1 的部份不做处理，不符合的剩余部份才进行转换
  • -d, –delete：删除指令字符
  • -s, –squeeze-repeats：缩减连续重复的字符成指定的单个字符
  • -t, –truncate-set1：削减 SET1 指定范围，使之与 SET2 设定长度相等
  • –help：显示程序用法信息
  • –version：显示程序本身的版本信息

字符集合的范围：

  • \NNN 八进制值的字符 NNN (1 to 3 为八进制值的字符)
  • \\ 反斜杠
  • \a Ctrl-G 铃声
  • \b Ctrl-H 退格符
  • \f Ctrl-L 走行换页
  • \n Ctrl-J 新行
  • \r Ctrl-M 回车
  • \t Ctrl-I tab键
  • \v Ctrl-X 水平制表符
  • CHAR1-CHAR2 ：字符范围从 CHAR1 到 CHAR2 的指定，范围的指定以 ASCII 码的次序为基础，只能由小到大，不能由大到小。
  • [CHAR*] ：这是 SET2 专用的设定，功能是重复指定的字符到与 SET1 相同长度为止
  • [CHAR*REPEAT] ：这也是 SET2 专用的设定，功能是重复指定的字符到设定的 REPEAT 次数为止(REPEAT 的数字采 8 进位制计算，以 0 为开始)
  • [:alnum:] ：所有字母字符与数字
  • [:alpha:] ：所有字母字符
  • [:blank:] ：所有水平空格
  • [:cntrl:] ：所有控制字符
  • [:digit:] ：所有数字
  • [:graph:] ：所有可打印的字符(不包含空格符)
  • [:lower:] ：所有小写字母
  • [:print:] ：所有可打印的字符(包含空格符)
  • [:punct:] ：所有标点字符
  • [:space:] ：所有水平与垂直空格符
  • [:upper:] ：所有大写字母
  • [:xdigit:] ：所有 16 进位制的数字
  • [=CHAR=] ：所有符合指定的字符(等号里的 CHAR，代表你可自订的字符)

使用实例

实例1：将文件testfile 中的小写字母全部转换成大写字母

        命令

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cat testfile|tr a-z A-Z

        输出

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$ 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. 
$ 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.

        也可以使用 [:lower:] [:upper:] 参数来实现

        命令

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

        输出

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$ 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.

        说明

        不过替换、删除、以及去重复都是针对一个字符来讲的，哟一定局限性。如果是针对一个字符串就不再管用了