redirect dev null variants
nohup gedit &> /dev/null
is POSIX syntax and is the same as:
nohup gedit & > /dev/null
That is run nohup gedit in background and then do a > /dev/null redirection without running a command.
nohup gedit >& /dev/null
is not POSIX syntax and is the csh way to redirect both stdout and stderr to /dev/null. csh doesn't have the 2>&1 operator as found in Bourne, so it's the only way csh has to redirect stderr.
zsh (as often) also provides with the csh syntax, but it also supports the x>&y fd duplication operator of the Bourne shell, which means there's a conflict there.
ls >&file
redirects ls's stdout and stderr to file, but if the file is 2, you've got a problem as
ls >&2
means redirect stdout to the resource pointed to by fd 2 (dup(2, 1)). So you need to write it:
ls >& ./2
if you wanted to redirect both the stdout and stderr of ls into a file called 2 in the current directory; or use the standard syntax.
bash initially did no understand >&, but it introduced the &> operator instead for that, breaking POSIX compliance in the process (though it's unlikely a script would use cmd &> xxx).
ksh copied that operator in ksh93t+ in 2009, mksh in R35 in 2008 (disabled in posix mode) but not >&.
bash added support for >& in 2.05.
busybox sh added support for both &> and >& in 1.13 (2008).
Neither >& nor &> as meaning redirect stdout and stderr are POSIX/Bourne.
If you want to redirect both stdout and stderr portably, the syntax is
cmd > file 2>&1