Master Linux Environment Variables: Permanent & Temporary Settings for Bash and Csh

Linux environment variable configuration can be divided into permanent and temporary variables, and the method depends on the shell type. This article outlines the steps for Bash (/bin/bash) and Csh (/usr/bin/csh) for both per‑user and system‑wide settings.

1. Bash (/bin/bash) – Permanent Variables – All Users / Single User

Step 1: Run echo $SHELL to confirm the current shell.

Step 2: For a single user, add export ORACLE_HOME=/home/oracle/base to .profile in the user’s home directory (create the file if it does not exist).

Step 3: For all users, add the same line to /etc/profile.

Step 4: Execute source .profile (or source /etc/profile) to apply the changes.

Step 5: Verify with echo $ORACLE_HOME.

$ echo $SHELL
/bin/bash
$ vi .profile   # add ORACLE_HOME
export ORACLE_HOME=/home/oracle/base
$ source .profile
$ echo $ORACLE_HOME
/home/oracle/base

2. Bash (/bin/bash) – Temporary Variables

Step 1: Confirm the shell with echo $SHELL.

Step 2: Set a temporary variable using export ORACLE_BASE="/opt/oracle/base". Note that the variable only lasts for the current shell session.

Step 3: Verify with echo $ORACLE_BASE.

$ echo $SHELL
/bin/bash
$ export ORACLE_BASE="/opt/oracle/base"
$ echo $ORACLE_BASE
/opt/oracle/base

3. Csh (/usr/bin/csh) – Permanent Variables – All Users / Single User

Step 1: Run echo $SHELL to ensure you are using Csh.

Step 2: Add setenv ORACLE_HOME /home/oracle/base to .cshrc in the user’s home directory (create the file if needed) for a single user.

Step 3: Apply the changes with source .cshrc.

Step 4: Verify with echo $ORACLE_HOME.

$ echo $SHELL
/usr/bin/csh
$ vi .cshrc   # add ORACLE_HOME
setenv ORACLE_HOME /home/oracle/base
$ source .cshrc
$ echo $ORACLE_HOME
/home/oracle/base

4. Csh (/usr/bin/csh) – Temporary Variables

Step 1: Confirm the shell with echo $SHELL.

Step 2: Set a temporary variable using ORACLE_BASE="/opt/oracle/base". This variable is only valid for the current session.

Step 3: Verify with echo $ORACLE_BASE.

$ echo $SHELL
/usr/bin/csh
$ ORACLE_BASE="/opt/oracle/base"
$ echo $ORACLE_BASE
/opt/oracle/base

(Source: https://www.cnblogs.com/linyfeng/p/10995761.html – © original author)