Two methods of shell script parameter passing based on arm5718

Preface
Usually, many scripts have parameter options , similar ：

./test.sh -f config.conf -v --prefix=/home
How to write this script ？

One 、Shell Explanation of special parameters
Let's start with a few special variables ：$0, $#, $*, [email protected], $?, $$, $_

Example 1： Create a new one test.sh The file of
#!/bin/bash
echo $0 # File name of the current script （ The indirect runtime also includes absolute paths ）.
echo $n # Parameters passed to a script or function .n It's a number , Indicates the number of parameters . for example , The first parameter is $1 .
echo $# # Number of arguments passed to script or function .
echo $* # All parameters passed to a script or function .
echo [email protected] # All parameters passed to a script or function . By double quotes (" ") Inclusion time , And $* Different , I'll talk about .
echo $? # Exit status of last command , Or the return value of the function .
echo $$ # At present Shell process ID. about Shell Script , It's the process of these scripts ID.
echo $_ # The last parameter of the last command
echo $! # Of the last process running in the background ID Number
The results are as follows ：

$ ./test.sh test test1 test2 test3 test4

./test.sh # $0
# $n
5 # $#
test test1 test2 test3 test4 # $*
test test1 test2 test3 test4 # [email protected]
0 # $?
12305 # $$
12305 # $_
# $!
$* and [email protected] Represents all parameters passed to a function or script ࿰