UNIX, get environment variable

Question

I have a ridiculous question due to a ridiculous problem.

Normally if I want to get the contents of an environment variable in a UNIX shell, I can do

echo ${VAR}

Let's assume, due to my ridiculous situation, that this isn't possible.

How do I get the contents of an environment variable to stdout, without someone who is looking at the command itself (not the output), see the value of the environment variable?

I can picture the solution being something like echo env(NAME_OF_VAR) although I can't seem to find it. The solution has to work in sh.

PS I can't write a script for this, it must be a built-in Unix command (I know, ridiculous problem).

Mike, are you ok? Are you being held with a gun to your head by the mafia in some warehouse? Is this a plea for help? — Tim Post, Mar 19 '10 at 13:49
What's the problem ? A keyboard where '{' is invisible / inaccessible ? — Frédéric Grosshans, Mar 19 '10 at 13:58
short answer, emergency bug fix at work. the practices at this place are terrible (understatement of the year). the purpose was to ensure a user wasn't seeing a password that was supposed to be hidden. the previous developer had set up the design so that it passed a plain-text password through stdin to the application. i get sick just thinking of it. anyway, i was able to use skwllsps suggestion. a horrible fix to a horrible problem resulting in a horrible company making horrible software. — Mike, Mar 19 '10 at 16:22
Another situation where this is useful: on Windows, environment variables may contain parentheses, and you cannot do *e.g.* `echo ${ProgramFiles(x86)}` because the shell will try to attempt a subsitution. However `printenv 'ProgramFiles(x86)'` works. — sam hocevar, Jan 30 '19 at 16:32

score 84 · Accepted Answer · edited Aug 30 '23 at 07:41

84

You can do:

printenv VARIABLE_NAME

edited Aug 30 '23 at 07:41

Gino Mempin

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answered Mar 19 '10 at 13:43

1

Ooh, something out of /usr/ucb. Impressive. – pra Mar 19 '10 at 22:28

score 13 · Answer 2 · answered Aug 01 '14 at 11:18

13

type the following command in terminal, it will display all the list of environment variables

printenv

now print the wanted variable like this:

echo $VARIABLENAME

answered Aug 01 '14 at 11:18

ASR

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score 9 · Answer 3 · answered Mar 26 '18 at 17:58

9

Using ${!VAR_NAME} should be what you are looking for

> FOO=BAR123
> VAR_NAME=FOO
> echo ${VAR_NAME}
FOO
> echo ${!VAR_NAME}
BAR123

answered Mar 26 '18 at 17:58

Ryan Anguiano

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score 4 · Answer 4 · answered Mar 19 '10 at 13:40

4

Do you mean something like this:

ENV() {
    printf 'echo $%s\n' $1 | sh
}

This works in plain old Bourne shell.

answered Mar 19 '10 at 13:40

mouviciel

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I'd use more quoting myself: `ENV() { printf 'printf "%%s\\n" "${%s}"\n' "$1" | sh; }` – glenn jackman Mar 19 '10 at 16:26

score 3 · Answer 5 · answered Mar 19 '10 at 13:36

3

How about this:

myVariable=$(env  | grep VARIABLE_NAME | grep -oe '[^=]*$');

answered Mar 19 '10 at 13:36

jens_profile

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actually you're probably better off using cut at the end e.g. ... | cut -d '=' -f2- – jens_profile Mar 19 '10 at 13:37

score 2 · Answer 6 · answered Mar 19 '10 at 13:56

2

The solution really depends on what the restrictions are why you can't use a simple $VAR. Maybe you could call a shell that doesn't have the restrictions and let this sub-shell evaluate the variable:

bash -c 'echo $VAR'

answered Mar 19 '10 at 13:56

sth

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user3061097 · Answer 7 · 2018-08-03T00:23:13.773

1

( set -o posix ; set ) | grep $var

search for all unix-compatible format variables been used

edited Aug 03 '18 at 00:23

answered Feb 13 '18 at 04:25

user3061097

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Code only answers are discouraged on StackOverflow. Please try to elaborate a little as to why this is a correct answer – Mittal Patel Feb 13 '18 at 04:34
1

Always remember to add explaination to the answer you post, so the users can understand the use of it. @user3061097 – LuFFy Feb 13 '18 at 06:41

UNIX, get environment variable

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