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

for these things, the gods are already in the chest, but there are some just contact Linux , Unix people like these systems may not be familiar with these variables, so I'll share them with you today. What problem can add QQ Group, we discuss together -- Ops tribe:348384728

To make it easier for everyone to understand, write a simple script that will explain the meaning of each variable later.

# Touch Test

# VI Test

The script reads as follows:

#!/bin/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: $?"

Save exit

Assigning script execution Permissions

# chmod +x Test

Execute script

#./test AA BB

Number:2
Scname:./test
First:aa
Second:bb
ARGUME:AA BB

Show Parm LIST:AA BB
Show Process id:24544

Show Precomm stat:0

By displaying the results you can see:

$#  is the number of arguments passed to the script

$ is the name of the script itself

$ is passed to the Shell the first parameter of a script

$ is passed to the Shell The second argument of a script

[email protected] is a list of all parameters passed to the script

$*  is to display all parameters passed to the script in a single string, unlike positional variables, where parameters can exceed 9 a

$$  is the current process that the script runs ID number

$?  is to display the exit status of the last command, 0 indicates no error, other indicates an error

This article is from "Old Gao Blog" blog, please be sure to keep this source http://12092502.blog.51cto.com/12082502/1943049

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