Input, Output, Redirection

I/O Name	Abbreviation	File Descriptor
Standard Input	stdin	0
Standard Output	stdout	1
Standard Error	stderr	2

> Redirects standard output to a file.
Overwrites (truncating) existing contents.
>> Redirects standard output to a file.
Appends to any existing contents.
< Redirects input from a file to a command. 

& Used with redirection to signal that a
file descriptor is being used.
2>&1 Combine stderr and standard output.
2>file Redirect standard error to a file.

>/dev/null Redirect output to nowhere.
$ ls here not-here 2> /dev/null
here
$ ls here not-here > /dev/null 2>&1

$ ls files.txt not-here 1>out 2>out.err