Bash Expansions

I'll come back to numbers before i post some cool features of bash.
Note that the '$' at the beginning of the line denotes the prompt.

1.Brace Expansion

$ echo alumn{a,i,ae,us}
alumna alumni alumnae alumnus

2.Tilde Exansion.

$ echo ~
/home/kalyan

3.Command substitution

$ ls $(which ls)
/bin/ls

Backticks also..

$ ls `which ls`
/bin/ls

4.Filename exapansion

$ ls s*
sd shift.sh string.sh stringcmp.sh
$ ls s?
sd
$ ls s[hd]*
sd shift.sh

5.Arithmetic Expansion
$ n=7
$ ((n=n+10))
$ echo $n
17

6.Paramenter expansion

$ ps=${ps:=lambadamda}
$ echo $ps
lambadamda