自訂 command

Valuable:
echo ${abc}
abc=iamabc
echo ${abc}


Export:
abc=iamabcecho ${abc}
//iamabc
bash
//進入到所謂的子程序
echo ${abc}
//null
exit
export abc
bash
echo ${abc}
//iamabc

alias:
alias react-native="node /path/to/this"
react-native