Get summary file for NCBI RefSeq genomes.

    wget ftp://ftp.ncbi.nlm.nih.gov/genomes/refseq/assembly_summary_refseq.txt

Grab the `ftp` path (and or any other fields you need) from this file for each genome.

    awk -F '\t' '{print $20}' assembly_summary_refseq.txt > ftp_paths

You should get something like this:

    ftp://ftp.ncbi.nlm.nih.gov/genomes/all/GCF/000/599/545/GCF_000599545.1_ASM59954v1
    ftp://ftp.ncbi.nlm.nih.gov/genomes/all/GCF/000/599/565/GCF_000599565.1_TruePyoMS2391.0
    ftp://ftp.ncbi.nlm.nih.gov/genomes/all/GCF/000/599/605/GCF_000599605.1_HJM029

From each of the ftp path directory you should be able to get the `*genomic.gff.gz` file for that genome.