可以使用以下6种方式，参考链接
http://www.cnblogs.com/wangyuyu/p/3791247.html
也可以用下面的方法：
require 'shell'
sh1 = Shell.new # Work in the current directory
sh2 = Shell.cd('/tmp/hal') # Work in /tmp/hal
sh = Shell.new
sh.cat('/etc/motd') > STDOUT
(sh.echo 'This is a test') > 'myfile.txt'
(sh.cat 'file1' 'file2') | (tee 'file3') > STDOUT
