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