Alternative content
curl 'ftp://ftp.ncbi.nlm.nih.gov/genomes/genbank/bacteria/assembly_summary.txt' | awk '{FS="\t"} !/^#/ {print $20}' | sed -r 's|(ftp://ftp.ncbi.nlm.nih.gov/genomes/all/)(GCA/)([0-9]{3}/)([0-9]{3}/)([0-9]{3}/)(GCA_.+)|\1\2\3\4\5\6/\6_genomic.fna.gz|' > genomic_file