#!/usr/bin/env python

import arvados

arvados.job_setup.one_task_per_input_file(if_sequence=0, and_end_task=True)

this_job = arvados.current_job()
this_task = arvados.current_task()
this_task_input = this_task['parameters']['input']
search_string = this_task['parameters']['pattern']

input_file = list(arvados.CollectionReader(this_task_input).all_files())[0]
out = arvados.CollectionWriter()
out.set_current_file_name(input_file.name())
out.set_current_stream_name(input_file.stream_name())
for line in input_file.readlines():
    if string.find(line, search_string):
        out.write(line)

this_task.set_output(out.finish())