You can use any one of the following command to display and list the shell environment variables and their values. The printenv command list the values of the specified environment VARIABLE(s). If no VARIABLE is given, print name and value pairs for them all.
- printenv command – Print all or part of environment.
- env command – Display all exported environment or run a program in a modified environment.
- set command – List the name and value of each shell variable.
| Tutorial details | |
|---|---|
| Difficulty | Easy (rss) |
| Root privileges | No |
| Requirements | Linux or Unix OS |
| Time | 1m |
Linux list all environment variables command
I recommend that you use the printenv command. The syntax is:
printenv printenv | less printenv | more
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.
| System Variable | Meaning | To view variable value type |
|---|---|---|
| BASH_VERSION | Holds the version of this instance of bash. | echo $BASH_VERSION |
| HOSTNAME | The name of the your computer. | echo $HOSTNAME |
| CDPATH | The search path for the cd command. | echo $CDPATH |
| HISTFILE | The name of the file in which command history is saved. | echo $HISTFILE |
| HISTFILESIZE | The maximum number of lines contained in the history file. | echo $HISTFILESIZE |
| HISTSIZE | The number of commands to remember in the command history. The default value is 500. | echo $HISTSIZE |
| HOME | The home directory of the current user. | echo $HOME |
| IFS | The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command. The default value is <space><tab><newline>. | echo $IFS |
| LANG | Used to determine the locale category for any category not specifically selected with a variable starting with LC_. | echo $LANG |
| PATH | The search path for commands. It is a colon-separated list of directories in which the shell looks for commands. | echo $PATH |
| PS1 | Your prompt settings. | echo $PS1 |
| TMOUT | The default timeout for the read builtin command. Also in an interactive shell, the value is interpreted as the number of seconds to wait for input after issuing the command. If not input provided it will logou user. | echo $TMOUT |
| TERM | Your login terminal type. | echo $TERM export TERM=vt100 |
| SHELL | Set path to login shell. | echo $SHELL |
| DISPLAY | Set X display name | echo $DISPLAY export DISPLAY=:0.1 |
| EDITOR | Set name of default text editor. | export EDITOR=/usr/bin/vim |
set and env command
You can use the env / set command too:
env env | more set set | more
Sample outputs:
HOME=/home/vivek vivek@nas01:~$ env TERM=xterm-256color SHELL=/bin/bash XDG_SESSION_COOKIE=9ee90112ba2cb349f07bfe2f00002e46-1381581541.324726-906214463 SSH_CLIENT=192.168.1.6 60190 22 SSH_TTY=/dev/pts/1 USER=vivek MAIL=/var/mail/vivek PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games PWD=/home/vivek LANG=en_IN SHLVL=1 HOME=/home/vivek LANGUAGE=en_IN:en LOGNAME=vivek SSH_CONNECTION=192.168.1.6 60190 192.168.1.10 22 _=/usr/bin/env
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:
printenv > env.txt cat env.txt
Use the grep command to search for particular variable:
printenv | grep foo printenv | grep HOME
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.
- Man pages: env(1)
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Thank you <3
thank you :)
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-limitsWhich gives out:
On my box it went up to 512MiB and failed with the following message (see image here)[1]:
Another command:
getconf -a |grep MAXSee the following man page:
man 2 execve