What is bang dollar (!$) in Bash?

Question

Bang dollar seems to refer to the last part of the last command line.

E.g.

$ ls -l
 .... something
$ !$
-l
bash: -l command not found

Answer 1

!$ can do what $_ does, except the fact that $_ does not store the value it returns (as its substitution) to history.

Here is an example.

With !$

za:tmep za$ ls -lad 
drwxr-xr-x  4 za  staff  136 Apr  6  2016 .
za:tmep za$ !$
-lad
-bash: -lad: command not found
za:tmep za$ history | tail -n 3
  660  ls -lad 
  661  -lad                     <<== history shows !$ substitution.  
  662  history | tail -n 3

With $_

za:tmep za$ ls -lad
drwxr-xr-x  4 za  staff  136 Apr  6  2016 .
za:tmep za$ $_
-bash: -lad: command not found
za:tmep za$ history | tail -n 3
  663  ls -lad
  664  $_         <<== history shows $_ and not its substitution. 
  665  history | tail -n 3
za:tmep za$ 

More options:

!^      first argument
!:2     second argument
!:2-$   second to last arguments
!:2*    second to last arguments
!:2-    second to next to last arguments
!:2-3   second to third arguments
!$      last argument
!*      all arguments