ZFS free space calculation when there are multiple datasets under the same path

[DonneyF]

I have the following zpool:

NAME     SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
cache    222G  67.4G   155G        -         -     0%    30%  1.00x    ONLINE  -

with the following datasets:

cache                     67.4G   148G     60.6G  /mnt/cache
cache/appdata             1.72G   148G     1.61G  /mnt/cache/appdata
cache/domains               96K   148G       96K  /mnt/cache/domains
cache/system              5.10G   148G     5.07G  /mnt/cache/system

I run YABS on /mnt/cache and encounter the following error:

bash: line 545: ((: 148G: value too great for base (error token is "148G")

The script continues normally afterwards. The issue is that free_space (https://github.com/masonr/yet-another-bench-script/blob/a18e1bcd60f5ab9e3640c650726d8949b7bb5bfe/yabs.sh#L535C3-L535C85) receives the following data:

148G
148G
148G
148

This is because the grep matches all entries. Perhaps a fix would be to also pipe head -n 1 or stricter grep arguments.