Complete Guide to Removing Environment Variables

To delete an exported environment variable in Unix/Linux systems, you can use the unset command followed by the variable name, such as unset GNUPLOT_DRIVER_DIR. For permanent removal, you’ll need to edit your shell startup files like .bashrc, .bash_profile, or .zshrc to remove the export statement that originally set the variable.

Contents

• Understanding Environment Variables
• Using the unset Command
• Removing Variables from Shell Startup Files
• Verifying Variable Removal
• Common Issues and Troubleshooting
• Differences Between Shell Types

Understanding Environment Variables

Environment variables are dynamic-named values that can affect the way running processes will behave on a Unix-like operating system. When you export a variable using the export command, it becomes available to all child processes of the current shell. This is why your GNUPLOT_DRIVER_DIR variable is still affecting your system even after the problematic installation attempt.

Environment variables can be:

• Session-specific: Only available in the current terminal session
• System-wide: Available to all users and processes
• User-specific: Available only to a particular user

For your GNUPLOT_DRIVER_DIR variable, it was likely set either in your user-specific configuration files or exported during your current session.

Using the unset Command

The most direct way to remove an environment variable from your current session is using the unset command:

unset GNUPLOT_DRIVER_DIR

This command removes the specified variable from the environment, making it unavailable to any new processes started from the current shell.

Key Points About unset:

• Immediate effect: The variable is removed immediately
• Session-specific: Only affects the current shell session
• No output: The command doesn’t produce any output when successful
• Case sensitivity: Variable names are case-sensitive

Example Usage:

# First, verify the variable exists
echo $GNUPLOT_DRIVER_DIR
# Output: /home/gnuplot/build/src

# Remove the variable
unset GNUPLOT_DRIVER_DIR

# Verify it's been removed
echo $GNUPLOT_DRIVER_DIR
# Output: (blank, no output)

Removing Multiple Variables:

unset VAR1 VAR2 VAR3

Removing Variables from Shell Startup Files

For permanent removal, you need to edit the shell configuration files where the variable was originally exported. The specific file depends on your shell and how you originally set the variable.

Common Shell Configuration Files:

• Bash: .bashrc, .bash_profile, .profile
• Zsh: .zshrc, .zprofile
• Fish: ~/.config/fish/config.fish
• Ksh: .profile, .kshrc

Steps to Remove from Configuration Files:

1. Identify which file contains the export statement:

   bash

   grep -n "GNUPLOT_DRIVER_DIR" ~/.bashrc ~/.bash_profile ~/.profile ~/.zshrc
   

2. Edit the appropriate file:

   bash

   nano ~/.bashrc  # or vim, emacs, etc.
   

3. Remove or comment out the export line:

   bash

   # Remove this line:
   export GNUPLOT_DRIVER_DIR="/home/gnuplot/build/src"
   
   # Or comment it out with #:
   # export GNUPLOT_DRIVER_DIR="/home/gnuplot/build/src"
   

4. Reload the configuration:

   bash

   source ~/.bashrc
   # or for zsh:
   source ~/.zshrc
   

Alternative Method for Bash:

You can use grep to find and remove the line:

# Find the line number first
grep -n "GNUPLOT_DRIVER_DIR" ~/.bashrc

# Then remove it using sed (replace X with the line number)
sed -i 'Xd' ~/.bashrc

Verifying Variable Removal

After removing a variable, you should verify that it’s been successfully deleted:

Immediate Verification:

# Check if variable is set
echo $GNUPLOT_DRIVER_DIR

# More detailed check
declare -p GNUPLOT_DRIVER_DIR 2>/dev/null || echo "Variable not set"

Check Current Environment:

# List all environment variables
env | grep GNUPLOT_DRIVER_DIR

# Or using printenv
printenv GNUPLOT_DRIVER_DIR

Check Configuration Files:

# Verify the line was removed from your startup files
grep -n "GNUPLOT_DRIVER_DIR" ~/.bashrc ~/.bash_profile ~/.profile ~/.zshrc

Common Issues and Troubleshooting

Variable Still Appears After unset:

If the variable reappears in new terminal sessions, it’s likely being set in a startup file.

Solution: Check all possible startup files:

# Check all common startup files
grep -r "GNUPLOT_DRIVER_DIR" ~/.bashrc ~/.bash_profile ~/.profile ~/.zshrc ~/.bash_login ~/.bash_logout ~/.pam_environment

Variable Set by System-wide Configuration:

If the variable is set in system-wide files like /etc/environment or /etc/profile:

1. Check system-wide locations:

   bash

   grep -r "GNUPLOT_DRIVER_DIR" /etc/environment /etc/profile /etc/profile.d/
   

2. Edit with administrator privileges:

   bash

   sudo nano /etc/environment
   # Remove the line with GNUPLOT_DRIVER_DIR
   

Variable Set by Another Process:

Some applications or scripts might be setting the variable dynamically.

Solution: Check for scripts that might be setting it:

# Check your PATH for scripts that might be setting it
which -a gnuplot 2>/dev/null | xargs grep -l "GNUPLOT_DRIVER_DIR" 2>/dev/null || echo "Not found in PATH"

Permission Issues:

If you can’t edit configuration files:

# Check permissions
ls -la ~/.bashrc

# Fix permissions if needed
chmod 644 ~/.bashrc

Differences Between Shell Types

Bash:

• Primary configuration files: .bashrc, .bash_profile
• Use unset for session removal
• Edit files for permanent removal

Zsh:

• Primary configuration files: .zshrc, .zprofile
• Similar syntax to bash
• May use unsetopt for shell options instead

Fish:

• Configuration file: ~/.config/fish/config.fish
• Syntax is different:
  fish

  # Remove from fish
  set -e GNUPLOT_DRIVER_DIR
  

Ksh:

• Configuration files: .profile, .kshrc
• Similar to bash but some differences in syntax

Environment Variables vs Shell Variables:

• Shell variables: Only available in current shell (no export)
• Environment variables: Available to child processes (with export)

To check if a variable is exported:

declare -p GNUPLOT_DRIVER_DIR | grep -q "export" && echo "Is exported" || echo "Not exported"

Conclusion

To remove the GNUPLOT_DRIVER_DIR environment variable, start with the immediate solution using unset GNUPLOT_DRIVER_DIR for the current session, then locate and edit the appropriate shell configuration file for permanent removal. Always verify the variable was successfully removed using echo $GNUPLOT_DRIVER_DIR or declare -p GNUPLOT_DRIVER_DIR. If issues persist, check all possible startup files and system-wide configuration locations. Remember that environment variable changes in configuration files only take effect in new terminal sessions or after sourcing the file with source ~/.bashrc.

Sources

Note: Due to web search quota limitations, specific online resources couldn’t be accessed for this answer. The information provided is based on standard Unix/Linux system administration practices and shell operation knowledge.

For authoritative guidance on environment variables and shell configuration, refer to:

1. Bash Manual - Environment Variables
2. Linux Environment Variables Guide
3. Unix Environment Variables Tutorial