Unix Environment Variables

• How do I show all my environment variables?
  set


• How do I show a specific environment variable, like PATH?
  set | grep -e "^PATH="


• How do I set an environment variable, like ORACLE_HOME?
  export ORACLE_HOME=/usr/oracle


• How do I delete a environment variable?
  unset ORACLE_HOME


• How do I append to an environment variable, like appending /users/sbin to PATH?
  export PATH=${PATH}:/users/sbin


• How do I reuse other environment variables, like adding ORACLE_HOME to PATH?
  export PATH=${PATH}:${ORACLE_HOME}


• How do I pass environment variables to Unix shell scripts without changing my environment?
  PATH=${PATH}:/usr/local ./myShellScript.sh


• How do I make my changes to environment variables permanent?
  Create or edit the file ~/.bashrc and add the export command to that file. For example, to make the change to ORACLE_HOME permanent, add the following line to ~/.bashrc
  export ORACLE_HOME=/usr/oracle
  
  After saving the file ~/.bashrc, then execute the command
  source ~/.bashrc


• What is the difference between ~/.bash_profile and ~/.bashrc? Or setting ~/.bashrc did not make my environment variable changes permanent.
  For a detailed explanation, please read Josh Staiger's article.
  
  But pragmatically it doesn't matter. Just make ~/.bash_profile execute ~/.bashrc. Create or edit ~/.bash_profile and add the following line
  [ -r ~/.bashrc ] && . ~/.bashrc