nf-core_modules/modules/samtools/view/main.nf

process SAMTOOLS_VIEW {
    tag "$meta.id"
    label 'process_low'

    conda (params.enable_conda ? "bioconda::samtools=1.15.1" : null)
    container "${ workflow.containerEngine == 'singularity' && !task.ext.singularity_pull_docker_container ?
        'https://depot.galaxyproject.org/singularity/samtools:1.15.1--h1170115_0' :
        'quay.io/biocontainers/samtools:1.15.1--h1170115_0' }"

    input:
    tuple val(meta), path(input), path(index)
    path fasta

    output:
    tuple val(meta), path("*.bam") , emit: bam , optional: true
    tuple val(meta), path("*.cram"), emit: cram, optional: true
    tuple val(meta), path("*.csi") , emit: csi,  optional: true
    path  "versions.yml"           , emit: versions

    when:
    task.ext.when == null || task.ext.when

    script:
    def args = task.ext.args ?: ''
    def args2 = task.ext.args2 ?: ''
    def prefix = task.ext.prefix ?: "${meta.id}"
    def reference = fasta ? "--reference ${fasta} -C" : ""
    def file_type = input.getExtension()
    if ("$input" == "${prefix}.${file_type}") error "Input and output names are the same, use \"task.ext.prefix\" to disambiguate!"
    """
    samtools \\
        view \\
        --threads ${task.cpus-1} \\
        ${reference} \\
        $args \\
        $input \\
        $args2 \\
        > ${prefix}.${file_type}

    cat <<-END_VERSIONS > versions.yml
    "${task.process}":
        samtools: \$(echo \$(samtools --version 2>&1) | sed 's/^.*samtools //; s/Using.*\$//')
    END_VERSIONS
    """

    stub:
    def prefix = task.ext.prefix ?: "${meta.id}"
    """
    touch ${prefix}.bam
    touch ${prefix}.cram

    cat <<-END_VERSIONS > versions.yml
    "${task.process}":
        samtools: \$(echo \$(samtools --version 2>&1) | sed 's/^.*samtools //; s/Using.*\$//')
    END_VERSIONS
    """
}