This is a compilation of a common patterns I use in my bash scripts:
Headline #
#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'
Logging #
log() {
echo "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $*"
}
err() {
echo "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $*" >&2
}
Confirmation prompt #
echo -n "Do something dangerous? [y/n]"
read -r ans
if [[ $ans != "y" ]]; then
exit 0
fi
Positional argument #
ARG=${1:-}
if [[ -z ${ARG} ]]; then
echo "usage: $0 [ARG]"
exit 1
fi
Random number #
readonly RANDOM_PORT=$(shuf -i 1024-49151 -n 1)
Check software availability #
if ! command -v aws>/dev/null; then
echo "AWS CLI is missing..."
fi
Redirect stderr to stdout #
0 */2 * * * /usr/local/bin/backup >> /var/log/cron.log 2>&1