Basic pipeline

This example shows a simple Nextflow pipeline consisting of two Bash processes.

#!/usr/bin/env nextflow

/*
 * Pipeline parameters
 */

// Primary input
params.greeting = "Hello World!"

/*
 * Redirect a string to a text file
 */
process sayHello {

    input:
    val x

    output:
    path 'output.txt'

    script:
    """
    echo '$x' > output.txt
    """
}

/*
 * Convert lowercase letters to uppercase letters
 */
process convertToUpper {

    input:
    path y

    output:
    stdout

    script:
    """
    cat $y | tr '[a-z]' '[A-Z]'
    """
}

/*
 * Workflow definition
 */
workflow {

    // Creates channel using the Channel.of() channel factory
    greeting_ch = Channel.of(params.greeting)

    // Redirects a string to a text file
    sayHello(greeting_ch)

    // Concatenates a text file and transforms lowercase letters to uppercase letters
    convertToUpper(sayHello.out)

    // View convertToUpper output
    convertToUpper.out.view()
}