learning shell built-in variables （1）

Shell built-in variables

【Purpose】

       Learning shell built-in variables, example $0,$1,$2,$3,$#,$$,$*,$@,$-,$?

 

【Eevironment】

       Ubuntu 16.04 bash env

 

【Procdeure】

Source code:

#!/bin/bash

echo "shell args option"
echo "script name : $0"
echo "first args : $1"
echo "first args : $2"
echo "first args : $3"

echo "------- \$# demonstration"
echo "args number: $#"


echo "------- \$\$ demonstration"
echo "shell pid: $$"

echo "------- \$* demonstration"
for i in "$*";do
echo $i
done

echo "------- \$@ demonstration"
for i in "$@";do
echo $i
done

echo "------- \$- demonstration"
echo $-

 

 

$ ./test.sh 1 2 3
shell args option
script name : ./test.sh
first args : 1
first args : 2
first args : 3
------- $# demonstration
args number: 3
------- $$ demonstration
shell pid: 12263
------- $* demonstration
1 2 3
------- $@ demonstration
1
2
3
------- $- demonstration
hB

vmuser@vmuser-virtual-machine:~/shell$ echo $?
0