main.nf

process A {
    input:
    val(i)

    output:
    path("output.${i}.txt")

    "echo hello $i > output.${i}.txt"
}

process B {
    storeDir 'store'

    input:
    path(infile)

    output:
    path("*.out")

    "cp $infile ${infile.baseName}.out"
}

process C {
    debug true

    input:
    path(infile)

    "ls"
}

workflow {
    Channel.of(params.input) | A | B | C
}