Calculate percentile in bash

percentile.sh

#!/bin/bash
# args are percentiles, stdin - integers one per line
set -o errexit
set -o nounset
set -o pipefail

tmp="$(mktemp -t percentile)"
trap "rm -f \"$tmp\"" EXIT
total=$(sort -n | tee "$tmp" | wc -l)

for percentile in "$@"; do
  # (n + 99) / 100 with integers is effectively ceil(n/100) with floats
  count=$(((total * percentile + 99) / 100))
  head -n $count "$tmp" | tail -n 1
done