params.bam = "$baseDir/data/bam/*.bam" log.info "bams files : ${params.bam}" Channel .fromPath( params.bam ) .ifEmpty { error "Cannot find any bam files matching: ${params.bam}" } .map { it -> [(it.baseName =~ /([^\.]*)/)[0][1], it]} .set { bam_files } process sort_bam { tag "$file_id" cpus 4 input: set file_id, file(bam) from bam_files output: set file_id, "*_sorted.bam" into sorted_bam_files script: """ sambamba sort -t ${task.cpus} -o ${file_id}_sorted.bam ${bam} """ }