How to expand variables from string?

[Olivier Langlois]

Hi,

First, sorry if I am cross-posting this question. I am not sure to
understand the difference between the 2 newsgroups.

My problem is that I have a shell variable containing a string
composed of variable names preceded with the expension operator ('$')
and I am fighting with the shell to find a way to make the expension.
Here is an example:

var1='$HOME'
echo $var1

will display $HOME but I would like to find a construction that would
allow me to print the $HOME value from the var1 variable.

Thank you for your assistance,
Olivier Langlois
http://www.olivierlanglois.net
http://blog.olivierlanglois.net

[Ralf Goertz]

Olivier Langlois wrote:

> Hi,
>
> First, sorry if I am cross-posting this question. I am not sure to
> understand the difference between the 2 newsgroups.
>
> My problem is that I have a shell variable containing a string
> composed of variable names preceded with the expension operator ('$')
> and I am fighting with the shell to find a way to make the expension.
> Here is an example:
>
> var1='$HOME'
> echo $var1
>
> will display $HOME but I would like to find a construction that would
> allow me to print the $HOME value from the var1 variable.

eval echo $var1

works for me

Ralf

[Crispie...@gmail.com]

Don't enclose the variable with quotes. For example:

HOME="Some Random Text"
TEST=$HOME
echo $TEST

This would then print the text "Some Random Text" without quotes which
is what you want ?

Glenn

[FrenKy]

This solution has one problem:

HOME="Some Random Text"
TEST=$HOME

HOME="Some Random Text"
echo $TEST

I'd use Ralf's suggestion.

[FrenKy]

HOME="Other Random Text"
echo $TEST

[William Pursell]

On 17 Oct, 03:24, Olivier Langlois <olangl...@sympatico.ca> wrote:
>
> First, sorry if I am cross-posting this question. I am not sure to
> understand the difference between the 2 newsgroups.

Unaware of the existence of alt.comp.lang.shell.unix.bourne-bash,
I am grateful to you for exposing me to it. (Or it to me, rather.)

> My problem is that I have a shell variable containing a string
> composed of variable names preceded with the expension operator ('$')
> and I am fighting with the shell to find a way to make the expension.

eval is your friend:

$ FOO="foo's text"
$ BAR='$FOO'
$ echo $BAR
$FOO
$ eval echo $BAR
foo's text

(Perhaps I should have used a character other than '$' for my
prompt...)

[haiyan...@gmail.com]

在 2007年10月17日星期三UTC+8上午11时24分35秒，Olivier Langlois写道：

Just try :
echo ${!var1}