Why Does System.getenv() Return Null on Mac Even When Environment Variables Are Set?

Why does System.getenv() return null even when the environment variable is correctly set?

String varValue = System.getenv("VAR_NAME");
System.out.println("Value: " + varValue);

The issue of System.getenv() returning null on MacOS when an environment variable seemingly exists can often be traced back to how and when the environment variable is set and accessed.

// Example of getting an environment variable in Java
String varValue = System.getenv("VAR_NAME");
System.out.println("Value: " + varValue);

Causes

• The environment variable may not be available in the context where the Java application is run, especially if it was set in a terminal session that does not propagate to the IDE.
• The Java application may need to be restarted to recognize the updated environment variables after changes are made in files like .bash_profile.
• There could be a discrepancy between the variable name as defined in the .bash_profile and the name used in the System.getenv() call.

Solutions

• Ensure that the environment variable is set in the correct shell configuration file such as .bash_profile or .bashrc and that these files are sourced correctly by the shell.
• Restart the IDE or terminal after setting the environment variable, as the Java runtime environment does not inherit variables from already running sessions.
• Double-check the casing and spelling of the variable name in both the .bash_profile and within the System.getenv() call.

Mistake: Assuming that changes to .bash_profile take effect immediately without restarting the terminal or IDE.

Solution: Run 'source ~/.bash_profile' in the terminal, or restart your IDE to ensure it reads the latest environment variable settings.

Mistake: Incorrect variable name spelling or case sensitivity when calling System.getenv().

Solution: Make sure the variable name in System.getenv() exactly matches that in .bash_profile, as it is case-sensitive.

Mistake: Assuming environment variables set in the terminal are accessible to an IDE without configuration.

Solution: Set environment variables in the IDE's run configuration settings, or ensure the IDE is launched from a terminal where the variables are set.