Run commands in parallel with xargs

#!/usr/bin/env bash
# Compress many log files in parallel with null-safe xargs.
set -euo pipefail

dir="${1:?usage: $0 DIR}"
jobs="${JOBS:-4}"

if [[ ! -d $dir ]]; then
  printf 'not a directory: %s\n' "$dir" >&2
  exit 1
fi

command -v gzip >/dev/null || { printf 'gzip is required\n' >&2; exit 1; }

# -print0 / -0 keep file names with spaces and newlines intact.
# xargs exits non-zero when any child fails, so set -e stops the script.
find "$dir" -type f -name '*.log' -print0 |
  xargs -0 -r -n 1 -P "$jobs" gzip -9 --

printf 'compressed .log files in %s using %s workers\n' "$dir" "$jobs"