dynamic-filename.nf

#!/usr/bin/env nextflow
/*
 * Copyright (c) 2013-2018, Centre for Genomic Regulation (CRG).
 * Copyright (c) 2013-2018, Paolo Di Tommaso and the respective authors.
 *
 *   This file is part of 'Nextflow'.
 *
 *   Nextflow is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   Nextflow is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with Nextflow.  If not, see <http://www.gnu.org/licenses/>.
 */

params.prefix = 'my'

data = 'Hello\n'

process foo {

  input:
  each x from 'alpha', 'delta', 'gamma', 'omega'
  file "${params.prefix}_${x}.txt" from data

  output:
  file "${params.prefix}_${x}.txt" into result

  """
  echo World >>  ${params.prefix}_${x}.txt
  """

}

result.subscribe {
  println "~ Saving ${it.name}"
  it.copyTo('.')
}