How to select different processes based on the number of files in channel.fromPath?

[ChenDepp]

hi:
How to select different processes based on the number of files in channel.fromPath?
Can you tell me how to achieve it?
hava a good day!

[mribeirodantas]

Create a folder, and store the following Nextflow code to a file named script.nf:

process A {
  debug true

  input:
  path filepath

  output:
  stdout

  script:
  """
  echo Less than 3: ${filepath}
  """
}

process B {
  debug true

  input:
  path filepath

  output:
  stdout

  script:
  """
  echo 3 or more: ${filepath}
  """
}

workflow {
  Channel
    .fromPath("*.txt")
    .set { my_ch }

  my_ch
    .collect()
    .branch {
        small: it.size() < 3
        large: it.size() >= 3
    }
    .set { result }

  A(result.small.flatMap())
  B(result.large.flatMap())
}

Create 2 .txt files (e.g. touch a.txt; touch b.txt) and run nextflow run script.nf and see what happens. Then create a third file (e.g. touch c.txt) and run it again. As you can see, we're using a different process depending on the number of elements in the channel created with the fromPath channel factory. Depending on what you want to do, you may need to adapt this code.

Also, please next time ask at https://community.seqera.io