Shell Programming and Scripting

Who can explain the meaning of the &2 &1 or @, #, etc in the script?
Is there any document which can explain the usage of these words in details?
for example:
ls /etc/sysconfig/network > /dev/null 2>&1
#@
bash, ksh and sh.

Thanks in advance for ur advice.

The first line

Code:

ls /etc/sysconfig/network > /dev/null 2>&1

would be used to find out if /etc/sysconfig/network exists or not
The output of ls is redirected to the bit bucket, and @>&1 redirects stderr (2) into stdout (1). This means that the ls command cannot produce anyout to the tty.

The "#@" -- if this is at the beginning of a line it's a comment, comments start with #.
If it's embedded somewhere in the middle of something like a regular expression, I have no idea.

What does this have to do with signals?