> 1. What does the 1+ in the shell expansion ${1+"$@"} mean and do?
http://unix.stackexchange.com/questions/68484/what-does-1-mean-in-a-shell-script-and-how-does-it-differ-from
> 2. I know that $0 returns the shell name or shell script file name. How does
> ${0##*/} differ in effect from $0.
It strips a leading path. $0 is the shell/script exactly as it was invoked.
$ pwd
/home/user
$ ../../bin/bash
[bash] $ echo $0
../../bin/bash
[bash] $ echo ${0##*/}
bash
[bash] $