System Tutorial
LINUX
What is the difference between an environment variable and a shell variable?
What is the difference between an environment variable and a shell variable?
Jul 21, 2025 am 03:35 AM
The difference between environment variables and shell variables is scope and availability. 1. Shell variables are only valid in the current shell session and are not passed to child processes or external programs. They are suitable for temporary storage or internal script logic; 2. Environment variables are exported shell variables that can be accessed in the current shell and all its child processes to configure application behavior. If you are not sure which variable to use, you can ask yourself "Whether the value needs to be visible outside the current shell", then use the environment variable, otherwise use the shell variable. The two are similar in appearance and operation, but the key difference is visibility and scope of action. Understanding this is crucial for debugging scripts and configuration tools.
The difference between an environment variable and a shell variable comes down to scope and availability. In short: environment variables are available system-wide (to the process and any child processes), while shell variables are local to the current shell session only .
What is a shell variable?
A shell variable is created and used within a specific shell session. It's useful for temporary storage or scripting purposes, but it doesn't get passed to other programs or subprocesses you might launch from that shell.
For example:
MY_VAR="hello" echo $MY_VAR
This creates a shell variable MY_VAR and then prints it. But if you try to access MY_VAR from a script or program launched from this shell, it won't be visible unless you explicitly export it.
Key points:
- Only accessible in the current shell.
- Not inherited by child processes.
- Useful for internal shell scripting logic.
What is an environment variable?
An environment variable is like a shell variable that has been exported so it's available not just in the shell, but also to any program or subprocess started from that shell.
To turn the earlier shell variable into an environment variable:
export MY_VAR="hello"
Now, any command or script you run from this shell can access MY_VAR .
Key points:
- Available to the shell and all its child processes.
- Used to configure behavior of applications and tools.
- Can be set temporarily in the shell or permanently in config files like
.bashrc,.zshrc, etc.
How do they appear and interact?
You can see environment variables using:
printenv
Or check both environment and shell variables with:
set
In practice, some variables start as shell variables and become environment variables when exported. Others are already set as environment variables by your login shell or system configuration.
Common environment variables include:
-
PATH– where the system looks for executable commands. -
HOME– the current user's home directory. -
USER– the current username.
Shell-only variables might include things like loop counters in scripts or temporary values that don't need to be shared.
When should you use each?
Use shell variables when:
- You're writing a script and need a temporary value.
- The value doesn't need to be seen by external commands.
- You're working interactively and just want to store something quickly.
Use environment variables when:
- You want a subprocess or program to have access to the value.
- You're configuring application behavior (like API keys or debug flags).
- You're setting up global settings that affect multiple tools or sessions.
If you're unsure, ask yourself: “Does this value need to be visible outside of my current shell context?” If yes → export it. If no → keep it local.
Basically that's it. They're similar in how they look and work, but the key difference lies in visibility and scope — and knowing which one you're using matters when debugging scripts or configuring tools.
The above is the detailed content of What is the difference between an environment variable and a shell variable?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Details on how to turn on environment variable settings on Windows 11
Dec 30, 2023 pm 06:07 PM
The environment variable function is an essential tool for running the configuration program in the system. However, in the latest win11 system, there are still many users who do not know how to set it up. Here is a detailed introduction to the location of the win11 environment variable opening. Come and join us. Learn to operate it. Where are the win11 environment variables: 1. First enter "win+R" to open the run box. 2. Then enter the command: controlsystem. 3. In the system information interface that opens, select "Advanced System Settings" from the left menu. 4. Then select the "Environment Variables" option at the bottom of the "System Properties" window that opens. 5. Finally, in the opened environment variables, you can make relevant settings according to your needs.
How to configure Tomcat environment variables
Oct 26, 2023 am 10:41 AM
To configure Tomcat environment variables, you need to add the CATALINA_HOME variable to the system and add the Tomcat installation path to the PATH variable. The steps in Windows are to first download and install Tomcat, open the system properties window, open the environment variable settings, add the Tomcat environment variable, modify the Path variable and verify the configuration. The steps in Linux are to first download and install Tomcat, open a terminal window, edit the bashrc file, add Tomcat environment variables, etc.
How to configure python environment variables in Win11? Tips for adding environment variables in win11python
Feb 29, 2024 pm 04:30 PM
Win11 system is the latest Windows operating system, and users may encounter some configuration problems when using it. Among them, configuring Python environment variables is a common requirement because it allows users to easily use Python commands from any location. This article will introduce how to configure Python environment variables in Win11 system so that users can use the Python programming language more conveniently. 1. [Right-click] this computer on the desktop, and select [Properties] in the menu item that opens; 2. Then, under related links, find and click [Advanced System Settings]; 3. In the system properties window, click [Environment] at the bottom Variables]; 4. In the environment variables window, under system variables, select [Path], and then click
How to set conda environment variables
Dec 05, 2023 pm 01:42 PM
Conda environment variable setting steps: 1. Find the installation path of conda; 2. Open the "System Properties" dialog box; 3. In the "System Properties" dialog box, select the "Advanced" tab, and then click the "Environment Variables" button; 4. In the "Environment Variables" dialog box, find the "System Variables" section, and then scroll to the "Path" variable; 5. Click the "New" button, and then paste the conda installation path; 6. Click "OK" to save the changes; 7. Verify whether the setting is successful.
Windows 10 environment variable setting tutorial
Jul 15, 2023 pm 06:09 PM
Environment variables are an important setting in the operating system, but some Windows 10 users still don’t know how to set environment variables. In fact, the method is very simple. Open the run window, call up the system characteristics window through the sysdm.cpl command, and then switch to the advanced tab. You will see a button for environment variables. Click this button to enter the setting of environment variables. interface, and then just set it up according to actual needs. How to set environment variables in Windows 10: 1. First open the run window on the computer, then enter sysdm.cpl in the window and press Enter. 2. Select Advanced in the system properties interface, and then click Environment Variables. 3. Here we can see the variables displayed, and we can create a new one on a single machine.
Steps to set the PATH environment variable of the Linux system
Feb 18, 2024 pm 05:40 PM
How to set the PATH environment variable in Linux systems In Linux systems, the PATH environment variable is used to specify the path where the system searches for executable files on the command line. Correctly setting the PATH environment variable allows us to execute system commands and custom commands at any location. This article will introduce how to set the PATH environment variable in a Linux system and provide detailed code examples. View the current PATH environment variable. Execute the following command in the terminal to view the current PATH environment variable: echo$P
How to solve the problem that Java environment variable configuration does not take effect
Feb 19, 2024 pm 10:57 PM
How to solve the problem that Java environment variables do not take effect after configuration. During the Java development process, we often need to configure Java environment variables to ensure the normal operation of the program. However, sometimes we encounter some strange problems. Even if the Java environment variables are configured correctly, we find that the program does not run as configured. This is actually a common problem, and this article will introduce some solutions and provide specific code examples. The root cause of the problem is that the configuration of Java environment variables does not take effect correctly. Here are some common
Practical tips to effectively solve Tomcat environment variable configuration failure
Dec 28, 2023 am 10:32 AM
Practical tips to solve the problem of unsuccessful configuration of Tomcat environment variables Summary: Tomcat is a very popular Java application server, but sometimes we may encounter some problems when configuring environment variables. This article will introduce several practical techniques to solve the problem of unsuccessful Tomcat environment variable configuration, and give specific code examples. Introduction: Tomcat is an open source web server used to run JavaWeb applications. However, when configuring Tomcat environment variables, you may sometimes encounter
