You can use this script that I wrote,
I'm using it as "active choice parameter" for Jenkins:
def sout = new StringBuilder(), serr = new StringBuilder()
def proc = 'aws s3 ls s3://bucket_name/'.execute()
proc.consumeProcessOutput(sout, serr)
proc.waitForOrKill(2000)
def values = "$sout".split('/')
def trimmedValues
def parameters=[]
values.each { println "${it}" }
def cleanValues = "$sout".split('PRE')
def last = cleanValues.last().split('2018-12-17')[0]
cleanValues.each { "${it}".toString();
trimmedValues = "${it}".trim();
parameters<<trimmedValues
}
parameters.remove(parameters.size() - 1);
parameters.add(last)
parameters
The "2018-12-17" split is because awscli returns the date at the end of the command:

This way I can use this parameter to determine what artifact/folder I'm taking from the bucket.
