How to get shell to self-detect using zsh or bash

Question

I've a question on how to tell which shell the user is using. Suppose a script that if the user is using zsh, then put PATH to his .zshrc and if using bash should put in .bashrc. And set rvmrc accordingly.

#!/usr/bin/env bash export PATH='/usr/local/bin:$PATH' >> ~/.zshrc source ~/.zshrc 

I've tried the following but it does not work : (

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 

Answer 1

If the shell is Zsh, the variable $ZSH_VERSION is defined. Likewise for Bash and $BASH_VERSION.

if [ -n "$ZSH_VERSION" ]; then    # assume Zsh elif [ -n "$BASH_VERSION" ]; then    # assume Bash else    # assume something else fi 

However, these variables only tell you which shell is being used to run the above code. So you would have to source this fragment in the user's shell.

As an alternative, you could use the $SHELL environment variable (which should contain absolute path to the user's preferred shell) and guess the shell from the value of that variable:

case $SHELL in */zsh)     # assume Zsh    ;; */bash)    # assume Bash    ;; *)    # assume something else esac 

Of course the above will fail when /bin/sh is a symlink to /bin/bash.

If you want to rely on $SHELL, it is safer to actually execute some code:

if [ -n "`$SHELL -c 'echo $ZSH_VERSION'`" ]; then    # assume Zsh elif [ -n "`$SHELL -c 'echo $BASH_VERSION'`" ]; then    # assume Bash else    # assume something else fi 

This last suggestion can be run from a script regardless of which shell is used to run the script.