main.nf

process A {
    input: val(name)
    output: tuple val(name), path("*")
    script: "echo hello $name > greeting.${name}.txt"
}

process B {
    input: val(name)
    output: tuple val(name), path("*")
    script: "echo goodbye $name > farewell.${name}.txt"
}

process C {
    input: tuple val(name), path(greeting), path(farewell)
    output: tuple val(name), path("all.txt")
    script: "cat $greeting $farewell > all.txt"
}

workflow {
    Channel.of("Rob", "Ben", "Nathan")
    | ( A & B )

    A.out 
    | join(B.out)
    | C
    | view
}