linux命令之tr命令用法总结

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。
tr命令常用来替换，删除来自标准输入字符串中的字符。注意，操作的单位是字符，不是字符串。也就是说，不管是替换还是删除，都是针对字符串中某个字符的。比如tr命令不能很方便地实现字符串替换：把“hello world”变成“hello beijing”，但是可以很方便地把每一个大写字符变成小写字符，echo “hello world” | tr ‘[a-z]’ ‘[a-z]’, 最后输出“hello world”。
语法
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：
cat testfile |tr a-z a-ztestfile文件中的内容如下：
$ 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 命令大小写转换后，得到如下输出结果：
$ 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.大小写转换，也可以通过[:lower][:upper]参数来实现。例如使用如下命令：
cat testfile |tr [:lower:] [:upper:]输出结果如下：
$ 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.删除windows文件“造成”的’^m’字符
cat $file_name | tr -d \r删除连续的字符
echo hhhhhh | tr -s [:alnum:]

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