bash3boilerplate/main.sh

#!/usr/bin/env bash
# BASH3 Boilerplate
#
# This file:
#  - Is a template to write better bash scripts
#  - Is delete-key friendly, in case you don't need e.g. command line option parsing
#
# More info:
#  - https://github.com/kvz/bash3boilerplate
#  - http://kvz.io/blog/2013/02/26/introducing-bash3boilerplate/
#
# Version 1.1.0
#
# Authors:
#  - Kevin van Zonneveld (http://kvz.io)
#  - Izaak Beekman (https://izaakbeekman.com/)
#  - Alexander Rathai (Alexander.Rathai@gmail.com)
#
# Usage:
#  LOG_LEVEL=7 ./main.sh -f /tmp/x -d
#
# Licensed under MIT
# Copyright (c) 2013 Kevin van Zonneveld (http://kvz.io)


### Configuration
#####################################################################

# Exit on error. Append ||true if you expect an error.
# `set` is safer than relying on a shebang like `#!/bin/bash -e` because that is neutralized
# when someone runs your script as `bash yourscript.sh`
set -o errexit
set -o nounset

# Bash will remember & return the highest exitcode in a chain of pipes.
# This way you can catch the error in case mysqldump fails in `mysqldump |gzip`
set -o pipefail
# set -o xtrace

# Environment variables and their defaults
LOG_LEVEL="${LOG_LEVEL:-6}" # 7 = debug -> 0 = emergency
NO_COLOR="${NO_COLOR:-}"    # true = disable color. otherwise autodetected

# Commandline options. This defines the usage page, and is used to parse cli
# opts & defaults from. The parsing is unforgiving so be precise in your syntax
# - A short option must be preset for every long option; but every short option
#   need not have a long option
# - `--` is respected as the separator between options and arguments
read -r -d '' usage <<-'EOF' || true # exits non-zero when EOF encountered
  -f --file  [arg] Filename to process. Required.
  -t --temp  [arg] Location of tempfile. Default="/tmp/bar"
  -v               Enable verbose mode, print script as it is executed
  -d --debug       Enables debug mode
  -h --help        This page
EOF

# Set magic variables for current file and its directory.
# BASH_SOURCE[0] is used so we can display the current file even if it is sourced by a parent script.
# If you need the script that was executed, consider using $0 instead.
__dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
__file="${__dir}/$(basename "${BASH_SOURCE[0]}")"
__base="$(basename ${__file} .sh)"
__os="Linux"
if [[ "${OSTYPE:-}" == "darwin"* ]]; then
  __os="OSX"
fi

### Functions
#####################################################################

function _fmt ()      {
  local color_debug="\x1b[35m"
  local color_info="\x1b[32m"
  local color_notice="\x1b[34m"
  local color_warning="\x1b[33m"
  local color_error="\x1b[31m"
  local color_critical="\x1b[1;31m"
  local color_alert="\x1b[1;33;41m"
  local color_emergency="\x1b[1;4;5;33;41m"
  local colorvar=color_$1

  local color="${!colorvar:-$color_error}"
  local color_reset="\x1b[0m"
  if [ "${NO_COLOR}" = "true" ] || [[ "${TERM:-}" != "xterm"* ]] || [ -t 1 ]; then
    # Don't use colors on pipes or non-recognized terminals
    color=""; color_reset=""
  fi
  echo -e "$(date -u +"%Y-%m-%d %H:%M:%S UTC") ${color}$(printf "[%9s]" ${1})${color_reset}";
}
function emergency () {                             echo "$(_fmt emergency) ${@}" 1>&2 || true; exit 1; }
function alert ()     { [ "${LOG_LEVEL}" -ge 1 ] && echo "$(_fmt alert) ${@}" 1>&2 || true; }
function critical ()  { [ "${LOG_LEVEL}" -ge 2 ] && echo "$(_fmt critical) ${@}" 1>&2 || true; }
function error ()     { [ "${LOG_LEVEL}" -ge 3 ] && echo "$(_fmt error) ${@}" 1>&2 || true; }
function warning ()   { [ "${LOG_LEVEL}" -ge 4 ] && echo "$(_fmt warning) ${@}" 1>&2 || true; }
function notice ()    { [ "${LOG_LEVEL}" -ge 5 ] && echo "$(_fmt notice) ${@}" 1>&2 || true; }
function info ()      { [ "${LOG_LEVEL}" -ge 6 ] && echo "$(_fmt info) ${@}" 1>&2 || true; }
function debug ()     { [ "${LOG_LEVEL}" -ge 7 ] && echo "$(_fmt debug) ${@}" 1>&2 || true; }

function help () {
  echo "" 1>&2
  echo " ${@}" 1>&2
  echo "" 1>&2
  echo "  ${usage}" 1>&2
  echo "" 1>&2
  exit 1
}

function cleanup_before_exit () {
  info "Cleaning up. Done"
}
trap cleanup_before_exit EXIT


### Parse commandline options
#####################################################################

# Translate usage string -> getopts arguments, and set $arg_<flag> defaults
while read line; do
  # fetch single character version of option sting
  opt="$(echo "${line}" |awk '{print $1}' |sed -e 's#^-##')"

  # fetch long version if present
  long_opt="$(echo "${line}" |awk '/\-\-/ {print $2}' |sed -e 's#^--##')"

  # map long name back to short name
  varname="short_opt_${long_opt}"
  eval "${varname}=\"${opt}\""

  # check if option takes an argument
  varname="has_arg_${opt}"
  if ! echo "${line}" |egrep '\[.*\]' >/dev/null 2>&1; then
    init="0" # it's a flag. init with 0
    eval "${varname}=0"
  else
    opt="${opt}:" # add : if opt has arg
    init=""  # it has an arg. init with ""
    eval "${varname}=1"
  fi
  opts="${opts:-}${opt}"

  varname="arg_${opt:0:1}"
  if ! echo "${line}" |egrep '\. Default=' >/dev/null 2>&1; then
    eval "${varname}=\"${init}\""
  else
    match="$(echo "${line}" |sed 's#^.*Default=\(\)#\1#g')"
    eval "${varname}=\"${match}\""
  fi
done <<< "${usage}"

# Allow long options like --this
opts="${opts}-:"

# Reset in case getopts has been used previously in the shell.
OPTIND=1

# Overwrite $arg_<flag> defaults with the actual CLI options
while getopts "${opts}" opt; do
  [ "${opt}" = "?" ] && help "Invalid use of script: ${@} "

  if [ "${opt}" = "-" ]; then
    # OPTARG is long-option-name or long-option=value
    if [[ "${OPTARG}" =~ .*=.* ]]; then
      # --key=value format
      long=${OPTARG/=*/}
      # Set opt to the short option corresponding to the long option
      eval "opt=\"\${short_opt_${long}}\""
      OPTARG=${OPTARG#*=}
    else
      # --key value format
      # Map long name to short version of option
      eval "opt=\"\${short_opt_${OPTARG}}\""
      # Only assign OPTARG if option takes an argument
      eval "OPTARG=\"\${@:OPTIND:\${has_arg_${opt}}}\""
      # shift over the argument if argument is expected
      ((OPTIND+=has_arg_${opt}))
    fi
    # we have set opt/OPTARG to the short value and the argument as OPTARG if it exists
  fi
  varname="arg_${opt:0:1}"
  default="${!varname}"

  value="${OPTARG:-}"
  if [ -z "${OPTARG:-}" ] && [ "${default}" = "0" ]; then
    value="1"
  fi

  eval "${varname}=\"${value}\""
  debug "cli arg ${varname} = ($default) -> ${!varname}"
done

shift $((OPTIND-1))

[ "${1:-}" = "--" ] && shift


### Switches (like -d for debugmode, -h for showing helppage)
#####################################################################

# debug mode
if [ "${arg_d}" = "1" ]; then
  set -o xtrace
  LOG_LEVEL="7"
fi

# verbose mode
if [ "${arg_v}" = "1" ]; then
  set -o verbose
fi

# help mode
if [ "${arg_h}" = "1" ]; then
  # Help exists with code 1
  help "Help using ${0}"
fi


### Validation (decide what's required for running your script and error out)
#####################################################################

[ -z "${arg_f:-}" ]     && help      "Setting a filename with -f or --file is required"
[ -z "${LOG_LEVEL:-}" ] && emergency "Cannot continue without LOG_LEVEL. "


### Runtime
#####################################################################

info "__file: ${__file}"
info "__dir: ${__dir}"
info "__base: ${__base}"
info "__os: ${__os}"

info "arg_f: ${arg_f}"
info "arg_d: ${arg_d}"
info "arg_v: ${arg_v}"
info "arg_h: ${arg_h}"

# All of these go to STDERR, so you can use STDOUT for piping machine readable information to other software
debug "Info useful to developers for debugging the application, not useful during operations."
info "Normal operational messages - may be harvested for reporting, measuring throughput, etc. - no action required."
notice "Events that are unusual but not error conditions - might be summarized in an email to developers or admins to spot potential problems - no immediate action required."
warning "Warning messages, not an error, but indication that an error will occur if action is not taken, e.g. file system 85% full - each item must be resolved within a given time. This is a debug message"
error "Non-urgent failures, these should be relayed to developers or admins; each item must be resolved within a given time."
critical "Should be corrected immediately, but indicates failure in a primary system, an example is a loss of a backup ISP connection."
alert "Should be corrected immediately, therefore notify staff who can fix the problem. An example would be the loss of a primary ISP connection."
emergency "A \"panic\" condition usually affecting multiple apps/servers/sites. At this level it would usually notify all tech staff on call."