Linux重定向命令介绍
see: https://unix.stackexchange.com/a/70971
2>&-
The general form of this one is M>&-, where "M" is a file descriptor number. This will close output for whichever file descriptor is referenced, i.e. "M".
2>/dev/null
The general form of this one is M>/dev/null, where "M" is a file descriptor number. This will redirect the file descriptor, "M", to /dev/null.
2>&1
The general form of this one is M>&N, where "M" & "N" are file descriptor numbers. It combines the output of file descriptors "M" and "N" into a single stream.
|&
This is just an abbreviation for 2>&1 |. It was added in Bash 4.
&>/dev/null
This is just an abbreviation for >/dev/null 2>&1. It redirects file descriptor 2 (STDERR) and descriptor 1 (STDOUT) to /dev/null.
>/dev/null
This is just an abbreviation for 1>/dev/null. It redirects file descriptor 1 (STDOUT) to /dev/null.