What does &> do in bash?

Question

I was looking at pre-commit hook and discovered the following line because I was wondering why I always got an empy file called 1 in my directory after doing a

Answer 1

&>word (and >&word redirects both stdout and stderr to the result of the expansion of word. In the cases above that is the file 1.

2>&1 redirects stderr (fd 2) to the current value of stdout (fd 1). (Doing this before redirecting stdout later in the line does not do what you might expect and will split the outputs instead of keeping them combined and is a very common shell scripting error. Contrast this to >word 2>&1 which combines the two fds into one sending to the same location.)

$ { echo stdout; echo stderr >&2; }
stdout
stderr
$ { echo stdout; echo stderr >&2; } >/dev/null
stderr
$ { echo stdout; echo stderr >&2; } >/dev/null 2>&1
$ 
{ echo stdout; echo stderr >&2; } 2>&1 >/dev/null
stderr

Not that those are, while similar looking, not the same thing.

git status 2&>1 > /dev/null is, in fact, actually running git status 2 with a redirection of &>1 (stdout and stderr to file 1). Almost certainly not what was intended. Your correction almost certainly is what was intended.

$ git init repro
Initialized empty Git repository in /tmp/repro/.git/
$ cd repro/
$ git status
# On branch master
#
# Initial commit
#
nothing to commit
$ ls
$ git status 2>&1
# On branch master
#
# Initial commit
#
nothing to commit
$ ls
$ git status 2&>1
$ ls
1
$ cat 1
# On branch master
#
# Initial commit
#
nothing to commit