You can set an environment variable on a Linux, Windows, or Mac platform with the instructions given below.
If you want to use Schrödinger applications using the command line, see this cheat sheet for an overview.
Linux
To set an environment variable on Linux, enter the following command at a shell prompt, according to which shell you are using:
csh/tcsh:
setenv variable value
bash/ksh: export variable=value
where variable is the name of the environment variable [such as SCHRODINGER] and value is the value you want to assign to the variable, [such as /opt/schrodinger2019-3]. To find out what environment variables are set, use the env command. To remove a variable from the environment, use the following commands:
csh/tcsh: unsetenv variable
bash/ksh: export -n variable
Windows
You can create or change environment variables in the Environment Variables dialog box. If you are adding to the PATH environment variable or any environment variable that takes multiple values, you should separate each value with a semicolon [;].
Windows 8 and Windows 10
To open the Environment Variables dialog box:
- In Search, search for and then select: Edit environment variables for your account
To create a new environment variable:
- In the User variables section, click New to open the New User Variable dialog box.
- Enter the name of the variable and its value, and click OK. The variable is added to the User variables section of the Environment Variables dialog box.
- Click OK in the Environment Variables dialog box.
To modify an existing environment variable:
- In the User variables section, select the environment variable you want to modify.
- Click Edit to open the Edit User Variable dialog box.
- Change the value of the variable and click OK. The variable is updated in the User variables section of the Environment Variables dialog box.
When you have finished creating or editing environment variables, click OK in the Environment Variables dialog box to save the values.
Windows 7
To open the Environment Variables dialog box:
- Click Start, then click Control Panel
- Click User Accounts.
- Click User Accounts again.
- In the Task side pane on the left, click Change my environment variables to open the Environment Variables dialog box opens.
To create a new environment variable:
- In the User variables section, click New to open the New User Variable dialog box.
- Enter the name of the variable and its value, and click OK. The variable is added to the User variables section of the Environment Variables dialog box.
- Click OK in the Environment Variables dialog box.
To modify an existing environment variable:
- In the User variables section, select the environment variable you want to modify.
- Click Edit to open the Edit User Variable dialog box opens.
- Change the value of the variable and click OK. The variable is updated in the User variables section of the Environment Variables dialog box.
When you have finished creating or editing environment variables, click OK in the Environment Variables dialog box to save the values. You can then close the Control Panel.
macOS
To set an environment variable on macOS, open a terminal window. If you are setting the environment variable to run jobs from the command line, use the following command:
export variable=value
where variable
is the name of the environment variable [such as SCHRODINGER] and value is the value you want to assign to the variable, [such as /opt/schrodinger/suites2019-3]. You can find out which
environment variables have been set with the env
command.
If you are setting the environment variable globally to use with applications, use the commands given below. The environment variables set by these commands are inherited by any shell or application.
macOS newer than 10.10
See this article for instructions on how to create a "plist" file to store system-wide environment variables in newer versions of macOS.
MacOS X 10.10
To set an environment variable, enter the following command:
launchctl setenv variable "value"
To find out if an environment variable is set, use the following command:
launchctl getenv variable
To clear an environment variable, use the following command:
launchctl unsetenv variable
Setting environment variables in Linux is a good way to define common and repetitive variables that are used across a number of applications and terminal commands. These environment variables help in cutting down verbosity, bring ease of use, and make development workflow better. An environment variable in Linux can be used to pass information or influence the behavior of an application or a process. This
article will explain various ways to set environment variables and how to use them. To set an environment variable for the shell currently in use, define a variable in the following format:
The definition is self explanatory, “MYVAR” is the variable name while “xyz” is its value. Running the command below will verify if the environment variable has been set correctly:
Notice the syntax of environment variables. While they work like any other shell variables, it is generally a good practice to use capital letters and underscores for left hand side [variable name].
To unset a variable, use the command below:
If you check the variable again using the echo command mentioned above, no output will be displayed. Note that unset will work for current terminal session only. If there are any global, system wide environment variables defined on your system, they will be available again in a new terminal session.
To set an environment variable for the shell currently in use and also for any child processes / shells launched from it, use a variable in the following format:
To permanently set an environment variable for bash shells [most default terminal apps in Linux distributions are configured for bash shell], add the variable [with “export” keyword] at the end of the hidden .bashrc file in your home directory.
You can edit .bashrc file by running the command below:
Replace “subl” with the command of your favorite text editor. You will need to reload .bashrc file to enable the changes. Run the command below to do so:
Below is an example of custom environment variables I have set for Ruby Gems.
You can view all environment variables enabled on your system by running the command below:
To specifically check if the custom environment variable added to .bashrc file has been enabled or not, run the command below:
To set an environment variable system wide for all apps, shells and processes, add your custom variable in “/etc/environment” file without “export” keyword.
You can edit “/etc/environment” file by running the command below:
$ sudo subl “/etc/environment”
Replace “subl” with your favorite text editor. You may need to reboot the system for the changes to take effect. To verify if your custom variable has been set correctly, run the command below:
Alternatively, you can use “printenv” command to verify the changes:
Note that the “unset” command explained above works for all custom environment variables, whether they are session specific or global variables. However, unset removes a variable for the running shell session only and it won’t remove any system wide or global variable permanently.
Some of the predefined environment variables in Ubuntu include:
- USER – name of the logged-in user
- HOME – home directory of logged in user [usually /home/username]
- DISPLAY – active monitor in use [usually automatically set by login manager]
- PWD – working directory where the shell is being used or invoked
- SHELL – shell that is being used system wide [usually /bin/bash]
- LANG – language used by the system [user defined, can be changed]
- PATH – scripts / binaries / executables are searched in the directories set in the PATH variable
Some of the environment variables that are commonly used to influence application behavior:
- LC_ALL – force overrides user defined locale with the value specified in the variable
- LD_LIBRARY_PATH – used to define additional directories where runtime libraries will be searched
- PATH – used to define additional directories where scripts / binaries / executables will be searched
- LD_PRELOAD – used to load custom / downgraded / upgraded libraries in an application
This marks the end of this article. Environment variables in Linux helps in running tweaked commands and applications without actually modifying underlying source and binaries by providing a way to define and use global variables across the system.
About the author
I am a freelancer software developer and content writer who loves Linux, open source software and the free software community.