My Bash script starter template

bash-starter-template.sh

#!/usr/bin/env bash

# See: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

# Set DEBUG to true for enhanced debugging: run prefixed with "DEBUG=true"
# Credits: https://github.com/ModusCreateOrg/devops-infra-demo
${DEBUG:-false} && set -o verbose; set -o xtrace

# Set CHECK to true to check script for syntax errors.
${CHECK:-false} && set -o noexec

# Any trap on ERR is inherited by shell functions, command substitutions, and
# commands executed in a subshell environment. The ERR trap is normally not
# inherited in such cases.
set -o errtrace

# Any trap on DEBUG and RETURN are inherited by shell functions, command
# substitutions, and commands executed in a subshell environment. The DEBUG and
# RETURN traps are normally not inherited in such cases.
set -o functrace

# Exit if any command exits with a non-zero exit status.
set -o errexit

# exit if script uses undefined variables.
set -o nounset

# prevent masking an error in a pipeline.
#
# look at the end of the 'Use set -e' section for an excellent explanation.
# see: https://www.davidpashley.com/articles/writing-robust-shell-scripts/
set -o pipefail

# less eager word splitting - no space.
IFS=$'\n\t'

# Make debugging easier when you use `set -x`
# See: http://wiki.bash-hackers.org/scripting/debuggingtips#making_xtrace_more_useful
export PS4='+(${BASH_SOURCE}:${LINENO}): ${FUNCNAME[0]:+${FUNCNAME[0]}(): }'

usage() {
  printf "USAGE:\n"
  printf "  %s ARG_1 [ARG_2] [ARG_3]\n\n" "$0"
}

do_something() {
  local arg
  arg="netstat"

  # credits: https://stackoverflow.com/a/677212/379786
  command -v "${port_command}" >/dev/null 2>&1 || { echo >&2 "${port_command}: command not found."; exit 127; }
}

main() {
  local required_arg
  local optional_arg
  local -i optional_int_arg

  required_arg="${1:?'ERROR: Argument #1 is reuquired. Dontyaknow?'}"
  optional_arg="${2:-foobar}"
  optional_int_arg="${3:-8080}"

  local result
  result=$(do_something}

  if [[ $result -eq 1 ]]; then
    usage
    printf "ERROR: Something could not be done!\n"
    exit 1
  fi
}

main "$@"
exit 0