常用linux 命令 -字符串相关

参考网络文章，个人工作总结

题记：一般对字符串的操作有以下几种：求长度，截取字符串，拼接字符串，找字符串中某个字符的索引

1 expr 命令

1.1 定义

man 手册

 Print  the  value  of  EXPRESSION to standard output.  A blank line below separates increasing precedence
       groups.  EXPRESSION may be:

       ARG1 | ARG2
              ARG1 if it is neither null nor , otherwise ARG2

       ARG1 & ARG2
              ARG1 if neither argument is null or , otherwise 

       ARG1 < ARG2
              ARG1 is less than ARG2
。。。等等
跟字符串相关的
  match STRING REGEXP
              same as STRING : REGEXP

       substr STRING POS LENGTH
              substring of STRING, POS counted from 

       index STRING CHARS
              index in STRING where any CHARS is found, or 

       length STRING
              length of STRING

1.2示例

[devtac@test_1 ~]$ expr length "how can i just let you walk away"
32

[devtac@test_1 ~]$ expr length "how "
4

[devtac@test_1 ~]$ expr substr "how can i just" 2 6
ow can
[devtac@test_1 ~]$ expr index "how can i how" h
1