Bash snippet to emit warning if capacity on disk(s) is ninety percent (90%) or more.

capacitOR.sh

#!/usr/bin/env bash
#
# capacitOR
#
# Emit warning if capacity on disk(s) is ninety percent (90%) or more.
#
# Author: M. Krinitz <mjk235 [at] nyu [dot] edu>
# Date: 22-Jul-2023
# License: MIT

# Set hostname, timestamp

host="$(hostname -f)"
timestamp="$(date +"%b %d %X")"

# Set threshold, e.g. 90%

limit=${1:-90}

# Assumed `df` columns are:
# "Filesystem" "1024-blocks" "Used" "Available" "Capacity" "Mounted on"
# df (limit to local filesystem; POSIX output; block size 1k)
# grep invert match
# read file line by line
# if capacity greater than or equal to threshold, do the dew

df --local --portability -k | grep -v '^Filesystem' | \
  while read -r Filesystem _ _ _ Capacity _ ; do
  [[ ${Capacity/\%/} -gt "${limit}" ]] && \
  printf "%s\n" "On $host@$timestamp ${Filesystem} is ${Capacity} full"

done