Usage of $ in Linux shell

The following lists the common methods of $

$n         represents the arguments passed to the script, representing the first one, and the second one ...
$#        represents the number of arguments passed to the script
$0          represents the name of the script.
$?         indicates the exit status of the last command, success is 0, otherwise 1
$$         indicates the ID number of the current program process
$!         represents the ID number of the last program process
[email  protected]       all parameters passed to the script

illustrate:

[email protected]:~$ VI 1. SH
#!usr/bin/bash-x
#!usr/bin/bash-x

echo "$$"
#!usr/bin/bash-x
Echo "$", "$";
echo "$#"
Echo "$"
test-e xyy.py
echo "$?"
echo "$$"
echo "[email protected]"

Plus permissions:

[email protected]:~$ chmod 777 1.sh

The corresponding output is as follows:

[email protected]:~$ bash 1.sh a b
a,b   
2
1.sh
1
4436
a b< /p>

Usage of $ in Linux shell