Setting linux display variable

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How To – Linux Set Environment Variables Command

1. Configure look and feel of shell.
2. Setup terminal settings depending on which terminal you’re using.
3. Set the search path such as JAVA_HOME, and ORACLE_HOME.
4. Create environment variables as needed by programs.
5. Run commands that you want to run whenever you log in or log out.
6. Set up aliases and/or shell function to automate tasks to save typing and time.
7. Changing bash prompt.
8. Setting shell options.

Two types of shell variables

• Environment variables (GLOBAL): Typically, end-users shouldn’t mess with Environment variables as they are available system-wide, and subshells and child processes can access them. In certain scenarios, we can modify them as per our needs. For example, we set up a system-wide path for the JAVA app or PATH for searching binaries. In almost all cases, we use the export command to define or modify environment variables.
• Shell and user-defined variables (LOCAL) : As the name suggests, these are defined by users and currently apply to the current shell session.

You can use the following commands to view and configure the environment.

Display current environment variables on Linux

The printenv command shows all or the given environment variables. Open the terminal prompt and then type:
printenv
printenv VAR_NAME
printenv PS1
printenv ORACLE_HOME
printenv JAVA_HOME
# use the grep command/egrep command to filter out variables #
printenv | grep APP_HOME
printenv | egrep ‘APP_HOME|DOCKER_HOME|NIX_BACKUP_HOST’

env command

The env command runs a Linux command with a modified environment. The syntax is:

Please note that If no command name is specified following the environment specifications, the resulting environment is displayed on screen. This is like specifying the printenv command as discussed earlier. For example:

How to set and list environment variables in Linux using set command

The env command/printenv command displays only the Linux shell environment variables. What if you need to see a list of all variables, including shell, environment, user-defined shell functions? Try the following set command for printing environment variables:
set
set | grep BASH
Here is what we see:

The $PATH defined the search path for commands. It is a colon-separated list of directories in which the shell looks for commands. The $PS1 defines your prompt settings. See the list of all commonly used shell variables for more information. You can display the value of a variable using the printf command or echo command:

Outputs from the last command displaying my home directory location set by the $HOME environment variable on Linux:
/home/vivek

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Linux List All Environment Variables Command

1. printenv command – Print all or part of environment.
2. env command – Display all exported environment or run a program in a modified environment.
3. set command – List the name and value of each shell variable.

Linux list all environment variables command

I recommend that you use the printenv command. The syntax is:

Fig.01: Command to see a list of all currently defined environment variables in a Linux bash terminal

A list of the commonly used variables in Linux

We use the printf command/echo command to display values of the shell varible in Linux.

set and env command

You can use the env / set command too:

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A note about env/set command

The env will only display a list of environment variables that have been exported and it will not show all bash variables. The set command allows you to change the values of shell options and set the positional parameters, or to display the names and values of shell variables. If no options or arguments are supplied, set displays the names and values of all shell variables and functions, sorted according to the current locale, in a format that may be reused as input for setting or resetting the currently-set variables. Hence, I recommend that you use printenv command to dump the list of all shell variables on screen. To save the list of all shell environment variables to a file, enter:

Use the grep command to search for particular variable:

Conclusion

You learned about listing all Linux shell environment variables. See the following resources for more information:

• Bash shell variables from the Linux shell scripting wiki.
• See the following man pages using the man command or help command:
  man ‘printenv(1)’
  man 1 bash
  man 1 env

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Comments on this entry are closed.

Thank you aref ghobadi Aug 18, 2015 @ 8:33

Thank you for this useful information.

Thank you.It’s really helpful.

Thank you. This is a very informative.

Note that set will show all unexported shell variables (e.g. like PS1 , TMOUT ) whereas env or printenv will not.

Thanks for the input 🙂

With environment variables, what’s the maximum amount of characters a environment variable can have?
and is it possible to set this higher?

The theoretical max length of an environment variable is around 32,760 characters. The maximum size of an environment variable value depends upon execve(). Try:
false | xargs —show-limits
Which gives out:

On my box it went up to 512MiB and failed with the following message (see image here)[1]:

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