Bash and variables

Question

Scenario

$ VAR1=test

$ VAR2=testing

$ VAR3=$VAR1_$VAR2

$ echo $VAR3

testing

I expected "test_testing" as the output. Why its not working? How to output in "test_testing" format? (make $VAR1_$VAR2 work)

Does it interprets VAR3=$VAR1_$VAR2 as VAR3=$(VAR1_$VAR2) ?

user729124 · Accepted Answer · 2011-07-11 15:57:13Z

10

Try

$ echo ${VAR1}_${VAR2}

Without the braces, it parses the combination as ${VAR1_}${VAR2}. Since you do not have a $VAR1_ variable defined, you see only the value of $VAR2.

You can see this if you define a variable $VAR1_:

$ VAR1_=another
$ echo $VAR1_$VAR2
anothertesting

answered Jul 11, 2011 at 15:57

user729124

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Comments

James.Xu · Accepted Answer · 2011-07-11 15:57:58Z

2

try:

VAR3="$VAR1"_"$VAR2"

it interprets VAR3=$VAR1_$VAR2 as $VAR1_ + $VAR2 --- there is no variable named $VAR1_

answered Jul 11, 2011 at 15:57

James.Xu

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1 Comment

carlspring Over a year ago

An alternative would be: VAR3=${VAR1}_${VAR2}

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