grim.sh

#!/usr/bin/env bash
set -x
set -euo pipefail

grim /tmp/output.png
imv -f /tmp/output.png &
p="$!"
g="$(slurp)"
kill "${p}"
offset="$(echo "${g}" | cut -d' ' -f1)"
left="$(echo "${offset}" | cut -d',' -f1)"
top="$(echo "${offset}" | cut -d',' -f2)"
dimensions="$(echo "${g}" | cut -d' ' -f2)"
convert "/tmp/output.png" -crop "${dimensions}+${left}+${top}" "/tmp/output2.png"
imv /tmp/output2.png