What does ENV=${deploy-qa} mean in bash? How does it evaluate to "qa"?

Asked Mar 11 '20 at 21:07

Active Mar 11 '20 at 21:16

Viewed 55 times

ENV=${deploy-qa}  
echo $ENV
qa

Relatively new to bash and I'm trying to set up a pipeline that switched based off the ending of a string and accidentally stumbled across this. I'm unsure how this actually returns 'qa' though. This is what I was looking to do, but I'd like to understand what's actually happening. I dont understand whats causing the 'deploy-' bit to drop off.

edited Mar 11 '20 at 21:14

Charles Duffy

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asked Mar 11 '20 at 21:07

themiDdlest

1

This is a parameter expansion. See https://wiki.bash-hackers.org/syntax/pe – Charles Duffy Mar 11 '20 at 21:15
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(the `:` is an optional modifier; its presence or absence determines whether the set-but-empty case is treated like the unset case). – Charles Duffy Mar 11 '20 at 21:17
@CharlesDuffy So 'qa' is the default parameter? – themiDdlest Mar 11 '20 at 21:20

What does ENV=${deploy-qa} mean in bash? How does it evaluate to "qa"?

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