UNIX, get environment variable

问题:

I have a ridiculous question due to a ridiculous problem.

Normally if I want to get the contents of an environment variable in 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)

Thanks (and sorry for the absurdity)

回答1:

You can do:

printenv VARIABLE_NAME

回答2:

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

回答3:

Do you mean something like this:

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

This works in plain old Bourne shell.

回答4:

How about this:

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

回答5:

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'

回答6:

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

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

回答7:

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

search for all unix-compatible format variables been used