什么是$在bash {0 ## ...}语法的变量，括号和散列字符的意义？ [英] What is the meaning of the ${0##...} syntax with variable, braces and hash character in bash?

问题描述

我刚刚看到在bash一些code，我听不太懂。作为新手的bash脚本编写者，我不知道发生了什么事。

 回声$ {0 ## / *}
回声$ {0}
 

我实在不明白，在这两个命令的输出（打印脚本名称）的差异。是＃只是一个评论？并与什么/ * 。如果是评论，为什么它不结束} 梅开二度干扰？

任何人都可以给我一些洞察到这种语法？

解决方案

请参阅相关章节子串去除高级Bash脚本编程指南：

  $ {串##串}
 

  
  

从$字符串前删除子的最长匹配。

*为通配符，匹配一切。命令 $ {0 ## / *} 打印 $ 0 的值，除非它以正斜杠开始，在这种情况下，打印什么。

I just saw some code in bash that I didn't quite understand. Being the newbie bash scripter, I'm not sure what's going on.

echo ${0##/*}
echo ${0}

I don't really see a difference in output in these two commands (prints the script name). Is that # just a comment? And what's with the /*. If it is a comment, how come it doesn't interfere with the closing } brace?

Can anyone give me some insight into this syntax?

解决方案

See the section on Substring removal in the Advanced Bash-Scripting Guide:

${string##substring}

Deletes longest match of substring from front of $string.

The * is a wildcard, matching everything. The command ${0##/*} prints the value of $0 unless it starts with a forward slash, in which case it prints nothing.

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