Shell脚本攻略学习笔记九之tr命令[待完善]

1. tr 命令的使用

  • 1.It can be used to perform substitution of characters,deletion of the characters, and squeezing of repeated characters from the standard input.
  • 2.tr accepts input only through stdin (standard input) and cannot accept input through command-line arguments.【tr命令仅仅支持标准输入，不支持参数输入】
  • 3.tr [options] set1 set2【如果set1 和 set2的长度不等，那么就会出现映射不匹配问题。】
  • 4.ROT13 is a well-known encryption algorithm. The ROT13 scheme performs alphabetic rotation of characters for 13 characters.【ROT13 是一个著名的加密算法。字母往后13的字母就是加密后的字符】
    如下这个就是使用ROT13作为加密算法使用，同时使用tr命令测试
[root@server4 backup]# echo "tr came, tr saw, tr conquered." | tr 'a-zA-Z' 'n-za-mN-ZA-M'
ge pnzr, ge fnj, ge pbadhrerq.
  • 将文件file.txt中的内容作为tr命令的输入，然后将其中的空格转换成+
[root@server4 backup]# tr ' ' '+' < file.txt
hello+spark+\n+hello+hadoop
hello+hive
-d 参数

tr has an option -d to delete a set of characters that appear on stdin by using the specified set of characters to be deleted as follows:

$ cat file.txt | tr -d '[set1]'
#Only set1 is used, not set2【只需要使用set1,不需要参数set2】
  • 将字符串中的指定内容删除
[root@server4 backup]# echo "hello 123 world 456" | tr -d '0-9'
hello  world
-c 参数

Here,the complement set is the set containing all numerals,space characters,and newline characters.All other characters are removed since -d is used with tr.
-c参数指定的集合会被保留
，

[root@server4 backup]# echo hello 1 char 2 next 4 | tr -d -c '0-9 \n'
 1  2  4
Here,the complement set is the set containing all numerals,space characters,and newline characters.All other characters are removed since -d is used with tr.
-s 参数

压缩重复的字符。
tr provides the -s option to squeeze repeating characters from the input.
$[ operation ] performs a numeric operation

[root@server4 shells]# cat sum.txt | echo $[ $(tr '\n' '+') 0 ]
15