Environment variable within variable

Question

I have an environment variable called $TEST which refers to a directory in my bash script I have a variable called $VARTEST which is $TEST/dir/file

now I want to grep the file specified by $VARTEST so I try to do:
grep somestring $VARTEST but it doesn't translate $TEST into it's directory

I've tried different combinations of {}, "" and '' but without success

Johannes Weiss · Accepted Answer · 2009-03-16 17:41:23Z

6

I think you want

eval grep somestring "$VARTEST"

or even

VARTEST_EVALUATED=$(eval echo $VARTEST)
grep "$SOMESTRING" "$VARTEST_EVALUATED"

but remember (as others already said): If possible use

VARTEST="$TEST/foo/bar"

instead of

VARTEST='$TEST/foo/bar'

use the second one only if you really need kind of 'lazy evaluation'...

Warning, this could be dangerous if $VARTEST contains malicous code.

edited Mar 16, 2009 at 17:41

answered Mar 16, 2009 at 17:10

Johannes Weiss

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2 Comments

Richo Over a year ago

that did the trick, however a new problem surfaced, somestring in my case is a variable which contains a whitespace $SOMESTRING = "some thing" now grep searches for some and uses thing as a filename, ie the ""'s are lost

Johannes Weiss Over a year ago

Ugly, but use eval grep "\"$SOMESTRING\"" "$VARTEST"

Ryan Bright · Accepted Answer · 2009-03-16 17:15:28Z

1

Have you put single quotes around something? Single quotes will prevent the variables from being translated into their corresponding values. Double quotes will work though. For example:

#!/bin/sh

TEST="/etc"
VARTEST="$TEST/passwd"
grep "$LOGNAME" "$VARTEST"

answered Mar 16, 2009 at 17:15

Ryan Bright

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