What is the meaning of variable $#,$@,$0,$1,$2,$*,$$,$ in Linux?

$# is the number of arguments passed to the script. $ is the name of the script itself. $ is the first parameter passed to the shell script, and the second argument that is passed to the shell script is [email protected] is a list of all the parameters passed to the script $* is to display all parameters passed to the script in a single string, unlike positional variables, which can be more than 9 $$ is the current process ID number for the script to run? is to display the exit status of the last command, 0 means no error, others indicate an error

Difference: [Email protected] $*

• Same point: All parameters are referenced
• Different points: only in double quotes. Assuming that three parameters were written when the script was run (stored in $ $ $), "$*" is equivalent to "$ $" (passing a parameter) and "[email protected]" is equivalent to "$" "$" "$" (three parameters passed)

Example One

# #dels. Sh
Echo "number:$#"Echo "scname:$0"Echo "First : $"Echo "second:$2"Echo "Argume:[email protected]"Echo "Show Parm list:$*"Echo "Show Process id:$$"Echo "Show Precomm stat: $?"

Execution results

[@jihite]$ sh del.sh 1 2 3number:3scname:del.shfirst:1second:2argume:1 2 3show parm list:1 2 3show process Id:21057show p Recomm stat:0

Example Two

#!/bin/SHNum=$ #name=$0Echo "Number : $num"Echo "scname: $name"Echo$0Echo$1Echo$2 for((i=0; i< $num; i++)) Do    Echo "$i" DoneEcho "Argume:[email protected]" forKeyinch[email protected] Do    Echo$key DoneEcho "-----------------" forKeyinch "[email protected]" Do    Echo$key DoneEcho "-----------------------------" forKey2inch$* Do     Echo$key 2 DoneEcho "-----------------" forKey2inch "$*" Do     Echo$key 2 DoneEcho "Show Process id:$$"ChoEcho "Show Precomm stat: $?"

Execution results

[@jihite]$ sh del.sh a b                                                       number:2scname:del.shdel.shab01argume:a Bab-----------------AB-----------------------------ab-----------------a bshow process id:23582del.sh:line 37:cho: Command not foundshow Precomm stat:127

Problem:

echo #0 #1 can you use $i to express it?

Linux variable $#,[email protected], meaning of $0,$1,$2,$*,$$,$?