Nextflow join file to tuple - nextflow

Question

I have problem with nextflow, I have a tuple with 3 elements (id, fastq_File, out_file) and I need join a new file to every tuple element (same file for all tuple element).
Well first I have a fastq, and I split this in chunks, and map with their id, after I have a process (simple process in the example), but this process return the id with other file.
reads = Channel.fromPath( 'data/illumina.fastq' )
.splitFastq(by: 150_000, file:true)
reads.map { it -> [it.name - ~/\.fastq/, it] }
.into{tuple_reads ; tuple_reads2}
process pr1 { /*is an example my real process is more complex*/
echo true
input:
tuple val(id), path(file) from tuple_reads
output:
tuple val(id), file("example${id}.out") into example_test
script:
"""
echo example${id} > example${id}.out
"""
}
readss = tuple_reads2.join(example_test)
I join the channels and I obtain something like this:
[illumina.1, /home/qs/work/../illumina.1.fastq, /home/qs/work/../exampleillumina.1.out]
[illumina.2, /home/qs/work/../illumina.2.fastq, /home/qs/work/../exampleillumina.2.out]
[illumina.3, /home/qs/work/../illumina.3.fastq, /home/qs/work/../exampleillumina.3.out]
Now, I have a channel with my id, the fastq file, and the out from process pr1, perfect for me, but this is the problem now, I need to create other process to run with a static file.
I need that every id run with the static_file but I don't know how do this. I need a new channel with something like this:
[illumina.1, /home/qs/work/../illumina.1.fastq, /home/qs/work/../exampleillumina.1.out,/home/qs/work/../static_file.txt]
[illumina.2, /home/qs/work/../illumina.2.fastq, /home/qs/work/../exampleillumina.2.out,/home/qs/work/../static_file.txt]
[illumina.3, /home/qs/work/../illumina.3.fastq, /home/qs/work/../exampleillumina.3.out,/home/qs/work/../static_file.txt]
or I need a process that repet the static file with every run.
The below code only run with the first element from the tuple :( (I tried with each but doesn't work.
process pr2 {
echo true
input:
tuple val(id), path(fastq_file), path(out_file) from example_test
path(st_file) from static_file
script:
"""
echo ${id} ${st_file}
"""
}
Thanks!!

Answer 1

You just need to make sure your second channel (i.e. the one for your static file) is a value channel. You didn't show how the static_file channel came was created, but you'll get the behaviour you're seeing if it's a regular queue channel, see here: Understand how multiple input channels work. To fix your example, all you need is:
static_file = file(params.static)
process pr2 {
echo true
input:
tuple val(id), path(fastq_file), path(out_file) from example_test
path(st_file) from static_file
script:
"""
echo ${id} ${st_file}
"""
}
Which is the same as:
static_file = file(params.static)
process pr2 {
echo true
input:
tuple val(id), path(fastq_file), path(out_file) from example_test
path static_file
script:
"""
echo ${id} ${static_file}
"""
}