linux查看是bash还是zsh,如何判断它是否使用zsh或bash 有大用

我有一个问题，如何告诉用户正在使用的shell。假设一个脚本，如果用户正在使用zsh，然后把PATH他的.zshrc和如果使用bash应放在.bashrc。并相应地设置rvmrc。

#!/usr/bin/env bash

export PATH='/usr/local/bin:$PATH'" >> ~/.zshrc

source ~/.zshrc

我试过以下，但它不工作：(

if [[ $0 == "bash ]]; then

export PATH='/usr/local/bin:$PATH'" >> ~/.bashrc

elif [[ $0 == "zsh" ]]; then

export PATH='/usr/local/bin:$PATH'" >> ~/.zshrc

fi

# ... more commands ...

if [[ $0 == "bash ]]; then

[[ -s '/Users/`whoami`/.rvm/scripts/rvm' ]] && source '/Users/`whoami`/.rvm/scripts/rvm'" >> ~/.bashrc

source ~/.bashrc

elif [[ $0 == "zsh" ]]; then

[[ -s '/Users/`whoami`/.rvm/scripts/rvm' ]] && source '/Users/`whoami`/.rvm/scripts/rvm'" >> ~/.zshrc

source ~/.zshrc

fi