main.sh

#!/usr/bin/env bash
# This file:
#
#  - Demos BASH3 Boilerplate (change this for your script)
#
# Usage:
#
#  LOG_LEVEL=7 ./main.sh -f /tmp/x -d (change this for your script)
#
# Based on a template by BASH3 Boilerplate v2.0.0
# Copyright (c) 2013 Kevin van Zonneveld and contributors
# http://bash3boilerplate.sh/#authors

# Exit on error. Append || true if you expect an error.
set -o errexit
# Exit on error inside any functions or subshells.
set -o errtrace
# Do not allow use of undefined vars. Use ${VAR:-} to use an undefined VAR
set -o nounset
# Catch the error in case mysqldump fails (but gzip succeeds) in `mysqldump |gzip`
set -o pipefail
# Turn on traces, useful while debugging but commented out by default
# set -o xtrace

# Set magic variables for current file, directory, os, etc.
__dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
__file="${__dir}/$(basename "${BASH_SOURCE[0]}")"
__base="$(basename ${__file} .sh)"

# The __os magic variable that b3bp offers is a dumbed down version of OSTYPE, aimed at
# simple use cases. For more specific os information use ${OSTYPE}, or uname directly.
if [[ "${OSTYPE:-}" == "linux"* ]]; then
  __os="Linux"
elif [[ "${OSTYPE:-}" == "darwin"* ]]; then
  __os="OSX"
elif [[ "${OSTYPE:-}" == "msys" ]]; then
  # This could accomodate Git Bash but we're welcoming more input at https://github.com/kvz/bash3boilerplate/issues/32
  __os="Windows"
elif [[ "${OSTYPE:-}" == *"bsd"* ]]; then
  __os="BSD"
else
  __os="b3bp_unsupported"
fi

# Define the environment variables (and their defaults) that this script depends on
LOG_LEVEL="${LOG_LEVEL:-6}" # 7 = debug -> 0 = emergency
NO_COLOR="${NO_COLOR:-}"    # true = disable color. otherwise autodetected


### 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:-No usage available}" 1>&2
  echo "" 1>&2
  echo " ${__helptext:-}" 1>&2
  echo "" 1>&2
  exit 1
}

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


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

# 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
# - We do not bash-expand defaults, so setting '~/app' as a default will not resolve to ${HOME}.
#   you can use bash variables to work around this (so use ${HOME} instead)
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
  -n --no-color    Disable color output
  -1 --one         Do just one thing
EOF
read -r -d '' __helptext <<-'EOF' || true # exits non-zero when EOF encountered
 This is Bash3 Boilerplate's help text. Feel free to add any description of your
 program or elaborate more on command-line arguments. This section is not
 parsed and will be added as-is to the help.
EOF

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

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

  # map long name back to short name
  varname="short_opt_${long_opt_mangled}"
  eval "${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

# start parsing command line
set +o nounset # unexpected arguments will cause unbound variables
               # to be dereferenced
# 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=${OPTARG/=*/}
      long_mangled="$(sed 's#-#_#g' <<< $long)"
      # Set opt to the short option corresponding to the long option
      eval "opt=\"\${short_opt_${long_mangled}}\""
      OPTARG=${OPTARG#*=}
    else
      # --key value format
      # Map long name to short version of option
      long_mangled="$(sed 's#-#_#g' <<< $OPTARG)"
      eval "opt=\"\${short_opt_${long_mangled}}\""
      # 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
set -o nounset # no more unbound variable references expected

shift $((OPTIND-1))

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


### Command-line argument 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

# no color mode
if [ "${arg_n}" = "1" ]; then
  NO_COLOR="true"
fi

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


### Validation. Error out if the things required for your script are not present
##############################################################################

[ -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."