Sort sequences by decreasing size annotation, which usually refers to the size of a cluster. The size is specified by a field size=N; in the sequence label, where N is an integer. The -minsize and -maxsize options can be used to specify a minimum and maximum size, respectively.
Output is written to a FASTA file using the -fastaout option and/or a FASTQ file using the -fastqout option.
The -relabel prefix option can be used to generate sequential labels for the sorted sequences. The output label is prefixN where N=1, 2, 3 etc. If -sizeout is used, a size annotation will be appended to the sequential label.
The -topn N option specifies that no more than N sequences should be output.
usearch -sortbysize seqs.fasta -fastaout seqs_sorted.fasta -minsize 4