检测：
$ env x='(){:;}; echo vulnerable' bash -c "echo this is a test"
中招的显示:
vulnerable
this is a test
如果是没有问题，则是下面：
$ env x='(){:;}; echo vulnerable' bash -c "echo this is a test"
bash: warning: x: ignoring function definition attempt
bash: error importing function definition for `x'
this is a test
提高Linux工作效率的十大bash技巧：http://www.linuxdiyf.com/linux/9096.html