Command based CLI bash skeleton

cli-app.bash

#!/bin/bash
# TEMPLATE_VERSION=2024-04-25

# Basic bash template for command/resource based CLI.
# Features:
# * Automatic command discovery and help generation
# * Logging and traces
# * Application dependency checker
# * Support for getopts
# * Return code support
# * Command executor with dry mode

set -eu

# App Global variable
# =================

APP_NAME="${0##*/}"
APP_AUTHOR="author"
APP_EMAIL="[email protected]"
APP_LICENSE="GPLv3"
APP_URL="https://github.com/$APP_AUTHOR/$APP_NAME"
APP_REPO="https://github.com/$APP_AUTHOR/$APP_NAME.git"
APP_GIT="[email protected]:$APP_AUTHOR/$APP_NAME.git"

APP_STATUS=alpha
APP_DATE="2023-01-01"
APP_VERSION=0.0.1

#APP_DEPENDENCIES="column tree htop"
APP_LOG_SCALE="TRACE:DEBUG:RUN:INFO:DRY:HINT:NOTICE:CMD:USER:WARN:ERR:ERROR:CRIT:TODO:DIE"

APP_DRY=${APP_DRY:-false}
APP_FORCE=${APP_FORCE:-false}
APP_LOG_LEVEL=INFO
#APP_LOG_LEVEL=DRY
#APP_LOG_LEVEL=DEBUG


# CLI libraries
# =================


_log ()
{
  local lvl="${1:-DEBUG}"
  shift 1 || true

  # Check log level filter
  if [[ ! ":${APP_LOG_SCALE#*$APP_LOG_LEVEL:}:$APP_LOG_LEVEL:" =~ :"$lvl": ]]; then
    if [[ ! ":${APP_LOG_SCALE}" =~ :"$lvl": ]]; then
      >&2 echo "  BUG: Unknown log level: $lvl"
    else
      return 0
    fi
  fi

  local msg=${*}
  if [[ "$msg" == '-' ]]; then
    msg="$(cat - )"
  fi
  while read -r -u 3 line ; do
    >&2 printf "%5s: %s\\n" "$lvl" "${line:- }"
  done 3<<<"$msg"
}

_die ()
{
    local rc=${1:-1}
    shift 1 || true
    local msg="${*:-}"
    if [[ -z "$msg" ]]; then
      [ "$rc" -ne 0 ] || exit 0
      _log DIE "Program terminated with error: $rc"
    else
      _log DIE "$msg"
    fi

    # Remove EXIT trap and exit nicely
    trap '' EXIT
    exit "$rc"
}

_exec ()
{
  local cmd=( "$@" )
  if ${APP_DRY:-false}; then
    _log DRY "  | ${cmd[@]}"
  else
    _log RUN "  | ${cmd[@]}"
    "${cmd[@]}"
  fi
}   


# shellcheck disable=SC2120 # Argument is optional by default
_dump_vars ()
{
  local prefix=${1:-APP_}
  declare -p | grep " .. $prefix" >&2 || {
      >&2 _log WARN "No var starting with: $prefix"
  }
}

_check_bin ()
{
  local cmd cmds="${*:-}"
  for cmd in $cmds; do
    command -v "$1" >&/dev/null || return 1
  done
}

# shellcheck disable=SC2120 # Argument is optional by default
_sh_trace ()
{
  local msg="${*}"

  (
    >&2 echo "TRACE: line, function, file"
    for i in {0..10}; do
      trace=$(caller "$i" 2>&1 || true )
      if [ -z "$trace" ] ; then
        continue
      else
        echo "$trace"
      fi
    done | tac | column -t
    [ -z "$msg" ] || >&2 echo "TRACE: Bash trace: $msg"
  )
}

# Usage: trap '_sh_trap_error $? ${LINENO} trap_exit 42' EXIT
_sh_trap_error () {
    local rc=$1
    [[ "$rc" -ne 0 ]] || return 0
    local line="$2"
    local msg="${3-}"
    local code="${4:-1}"
    set +x

    _log ERR "Uncatched bug:"
    _sh_trace # | _log TRACE -
    if [[ -n "$msg" ]] ; then
      _log ERR "Error on or near line ${line}: ${msg}; got status ${rc}"
    else
      _log ERR "Error on or near line ${line}; got status ${rc}"
    fi
    exit "${code}"
}

# Extra libs
# =================

# Ask the user to confirm
_confirm () {
  local msg="Do you want to continue?"
  >&2 printf "%s" "${1:-$msg}"
  >&2 printf "%s" "([y]es or [N]o): "
  >&2 read REPLY
  case $(echo $REPLY | tr '[A-Z]' '[a-z]') in
    y|yes) echo "true" ;;
    *)     echo "false" ;;
  esac
}


# Ask the user to input string
_input () {
  local msg="Please enter input:"
  local default=${2-}
  >&2 printf "%s" "${1:-$msg}${default:+ ($default)}: "
  >&2 read REPLY
  [[ -n "$REPLY" ]] || REPLY=${default}
  echo "$REPLY"
}


_yaml2json ()
{
  python3 -c 'import json, sys, yaml ; y = yaml.safe_load(sys.stdin.read()) ; print(json.dumps(y))'
}

# CLI API
# =================

cli__help ()
{
  : ",Show this help"

  cat <<EOF
${APP_NAME:-${0##*/}} is command line tool

usage: ${0##*/} <COMMAND> <TARGET> [<ARGS>]
       ${0##*/} help

commands:
EOF

  declare -f | grep -E -A 2 '^cli__[a-z0-9_]* \(\)' \
    | sed '/{/d;/--/d;s/cli__/  /;s/ ()/,/;s/";$//;s/^  *: "//;' \
    | xargs -n2 -d'\n' | column -t -s ','

  cat <<EOF

info:
  author: $APP_AUTHOR ${APP_EMAIL:+<$APP_EMAIL>}
  version: ${APP_VERSION:-0.0.1}-${APP_STATUS:-beta}${APP_DATE:+ ($APP_DATE)}
  license: ${APP_LICENSE:-MIT}
EOF
}



# CLI Commands
# =================

cli__example ()
{
  : "[ARG],Example command"

  local arg=${1}
  echo "Called command: example $arg"
}


# Core App
# =================

app_init ()
{
  # Useful shortcuts
  export GIT_DIR=$(git rev-parse --show-toplevel 2>/dev/null)
  export SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
  export WORK_DIR=${GIT_DIR:-${SCRIPT_DIR:-$PWD}}
  export PWD_DIR=${PWD}
}


app_main ()
{

  # Init
  trap '_sh_trap_error $? ${LINENO} trap_exit 42' EXIT
  
  # Read CLI options
  local -a args
  while [[ "$1" != "" ]]; do
    case "$1" in
      -h|--help)
        cli__help; 
        _die 0
        ;;
      -n|--dry)
        _log INFO "Dry mode enabled"
        APP_DRY=true 
        shift
        ;;
      -f|--force)
        _log INFO "Force mode enabled"
        APP_FORCE=true 
        shift
        ;;
      -v|--verbose)
        [[ ! -z "${2:-}" ]] || _die 1 "Missing log level value"
        _log INFO "Log level set to: $2"
        APP_LOG_LEVEL=$2 
        shift 2
        ;;
      -*)
        _die 1 "Unknown option: $1"
        ;;
      *)
        args+=("$1")
        shift
      ;;
    esac
  done
  
  # Route commands before requirements
  local cmd=${1:-help}
  shift 1 || true
  case "$cmd" in
    -h|--help|help) cli__help; return ;;
    # expl) cli__example "$@"; return ;;
  esac
  
  # Init app
  app_init
  
  # Define requirements
  local prog
  for prog in ${APP_DEPENDENCIES-} ; do
    _check_bin $prog || {
      _log ERROR "Command '$prog' must be installed first"
      return 2
    }
  done

  # Search and prepare command to run
  if [[ $(type -t "cli__${cmd}") == function ]]; then
    "cli__${cmd}" "$@" || {
      _die $? "Command returned error: $?"  
    }
  else
    _die 3 "Unknown command: $cmd"
  fi

}


app_main "${@}"