Linux tr命令

灰太狼 2020-05-26 14:00 522阅读 0赞

# Linux tr命令

[![Linux 命令大全](/images/1590082124592.gif "Linux 命令大全") Linux 命令大全](/queryGroupArticle/525090658056452/525103003242112)

Linux tr 命令用于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，经过字符串转译后，将结果输出到标准输出设备。

### 语法

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

**参数说明：**

- -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)

### 实例

将文件testfile中的小写字母全部转换成大写字母，此时，可使用如下命令：

```shell
cat testfile |tr a-z A-Z 
```

testfile文件中的内容如下：

```shell
$ 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 命令大小写转换后，得到如下输出结果：

```shell
$ 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. 
```

大小写转换，也可以通过`[:lower][:upper]`参数来实现。例如使用如下命令：

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

输出结果如下：

```shell
$ 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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