Solution
process '6C_ASE_knownSNPs' { tag "$sampleId" publishDir "$params.results/$sampleId" input: file genome from genome_file file index from genome_index_ch file dict from genome_dict_ch set sampleId, file(vcf), file(bam), file(bai) from grouped_vcf_bam_bai_ch output: file "ASE.tsv" script: """ echo "${bam.join('\n')}" > bam.list java -jar $GATK -R ${genome} \ -T ASEReadCounter \ -o ASE.tsv \ -I bam.list \ -sites ${vcf} """ }