http://www.xaprb.com/blog/2006/06/06/what-does-devnull-21-mean/)
Example command:
cmd > file 2>&1
Output redirection
There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors are often called STDIN(0), STDOUT(1), and STDERR(2), and use 0,1,2 to represent correspondingly.
by default, it looks like
Given that context, you can see the command above is redirecting standard output into file, then redirecting standard error into standard output (you have to put an & in front of the destination when you do this). It looks like
if the commnd is cmd <>&1, the it looks like
