no output foler

[Malabady]

Hi,
I am using the following command:

/RATTLE-1.0/rattle cluster --input all_fastq_pass_filtered.fq --threads 24 --iso --rna --output ./rattle_output

the command gives these following messages:

RNA mode: true
Reading fasta file... Done
Gene clustering done
21698 gene clusters found

However, no clusters are written in the output folder. the output folder is totally empty. when I remove the output folder, assuming the the command will create it, the run finishes with above messages but without an output folder.

What's happening?

thanks