"Turn" stdin, stdout, stderr and redirect

See more: http://my.oschina.net/qihh/blog/55308

STDIN is standard input file, stdout is standard output file, stderr standard error file.

The programs use these files as follows:

• The standard input is where the program can read its input. By default, the process reads stdin from the keyboard.

• The standard output is where the program writes its output. By default, the process writes stdout to the terminal screen.

• The standard error is where the program writes its error message. By default, the process writes stderr to the terminal screen.

"Turn" stdin, stdout, stderr and redirect