How to concatenate a string with a variable to the new variable in Bash?

Question

I have a shell script like this,

#!/bin/bash
foxy1="foxyserver"
H="1"

and the output should be foxyserver.

I tried this,

echo $foxy$H

and this gives me

and then I used

str="foxy$H"
echo $str

the output is

foxy1

How could I do that?

Charles Duffy · Accepted Answer · 2013-05-31 03:25:41Z

6

Use indirect variables, as described in BashFAQ #6:

$ foxy1="foxyserver"
$ H="1"
$ varname="foxy$H"
$ echo "${!varname}"
foxyserver

answered May 31, 2013 at 3:25

Charles Duffy

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Comments

perreal · Accepted Answer · 2013-05-31 03:36:43Z

2

Using eval, you can do indirection:

eval echo \$$str

Output

foxyserver

Warning: This is not really good practice. For example, if you have str=(rm -rf ~/*) then the eval expression would be $(rm -rf ~/*). So be warned and use indirection as suggested by Charles Duffy.

edited May 31, 2013 at 3:36

answered May 31, 2013 at 3:24

perreal

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1 Comment

Charles Duffy Over a year ago

From a security perspective, this is bad practice. Indirect variables would only let you name a variable to be expanded, whereas eval lets your variables' contents do literally anything.

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