A Wonderful Post on Stdin

The following is a wonderful post on stdin, stdout, stderr.

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http://www.jstorimer.com/blogs/workingwithcode/7766119-when-to-use-stderr-instead-of-stdout

Notes:

1.[-n string] 将会测试string的长度,如果大于0, 则返回true

2.awesome os-x command line:

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https://github.com/herrbischoff/awesome-osx-command-line