[原创]PowerShell中负数索引生成子串的办法

作者: Edengundam(马涛)

本篇文章引用的小例子来自如下链接:

http://bbs.chinaunix.net/viewthread.php?tid=957849&extra=page%3D1

 

Bash 裡有變量擴展 ${var:offset:length} ${var:offset}

 

[victor@localhost ~]$ echo ${USER}
victor
[victor@localhost ~]$ echo ${USER:1}
ictor
[victor@localhost ~]$ echo ${USER:5:1}
r
[victor@localhost ~]$ echo ${USER:(-1)}
r
[victor@localhost ~]$ echo ${USER:(-2)}
or
[victor@localhost ~]$ echo ${USER:(-5)}
ictor
[victor@localhost ~]$


如何使用PowerShell完成呢??

PS C:/> "victor"
victor
PS C:/> "victor".SubString(1);
ictor
PS C:/> "victor".SubString(5,1);
r

对于使用负数做索引, .Net Framework的System.String中几个实例方法都不支持. 只好先用slices获取负数索引, 然后用System.String提供的静态方法Join连接起来.

PS C:/> [string]::join('', ('victor')[-5..-1])
ictor
PS C:/> [string]::join('', ('victor')[-2..-1])
or
PS C:/> [string]::join('', ('victor')[-1..-1])
r

当然这几个例子比较简单, 有时间我还会添加更多的例子.