Bash utils lib

bash_lib_app.sh

# Logging and User interactions
# ==============
_log ()
{
  local lvl=${1:-DEBUG}
  shift 1 || true
  local msg=${*}
  if [[ "$msg" == '-' ]]; then
    msg=$(cat - )
  fi
  while read -u 3 line; do
    >&2 printf '%-8s: %s\n' "$lvl" "${line:- }"
  done 3<<<"$msg"
}

_log INFO "Hello world"
cat "Hello" | _log DEBUG -


_ask_to_continue ()
{
  ${RESTRAP_DRY:-false} && return || true

  local msg="${1}"
  local waitingforanswer=true
  while ${waitingforanswer}; do
    read -r -p "${msg}"$'\n(hit "y/Y" to continue, "n/N" to cancel) ' -n 1 ynanswer
    case ${ynanswer} in
      [Yy] ) waitingforanswer=false; break;;
      [Nn] ) echo ""; echo "Operation cancelled as requested!"; return 1;;
      *    ) echo ""; echo "Please answer either yes (y/Y) or no (n/N).";;
    esac
  done
  echo ""
}


# Dry mode
# ==============
_exec ()
{
  local cmd=$@

  if ${APP_DRY:-false}; then
    _log DRY "$cmd"
  else
    _log RUN "$cmd"
    $cmd
  fi
}


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



# Coding practices
# ==============

# Nested whiles
nested_whiles ()
{
  local a="1
  2
  3"
  local b="4
  5
  6"
  while IFS=$' \t\n' read -r n1; do
    echo "$n1      Chapter"
    while IFS=$' \t\n' read -r -u 3 n2; do
      echo "  $n1.$n2    Section"
    done 3<<<"$b"
  done <<< "$a"
}


# Log to stderr
>&2 echo "My message"


# Bash debugging
# ==============
_dump_vars ()
{
  local prefix=${1:-_}
  declare -p | grep " .. $prefix"
}



# Lock functions
# ====================

LOCK_FILE='/tmp/.lock_my_script'

function wait_lock ()
{
  local tmout=${1:-60}

  >&2 echo -n "INFO: Waiting for lock (${tmout}s) ..."
  while ! lock 2>/dev/null ; do
    if [[ "$tmout" < 1 ]]; then
      >&2 echo -e "\nERROR: Lock timout expired, could not execute"
      return 1
    fi

    >&2 echo -n "."
    sleep 1
    tmout=$(( tmout - 1 ))
  done

  # Do the last line return
  >&2 echo " unlocked!"
  
}

function lock() {

    if [[ -f ${LOCK_FILE} ]]; then
        local curr_proc=$( cat "${LOCK_FILE}" )
        if kill -0 $curr_proc >&/dev/null; then
          >&2 echo "ERROR: ${LOCK_FILE} already exists, please stop pid [$(cat ${LOCK_FILE})] before continue."
          return 1
        else
          >&2 echo "INFO: emove ${LOCK_FILE} as '$curr_proc' does not exist anymore"
          rm "${LOCK_FILE}"
        fi
    else
        echo "$$" > ${LOCK_FILE}
    fi
    trap unlock EXIT
}

function unlock() {
    [[ -f $LOCK_FILE ]] || return 0
    >&2 echo "INFO: Release lock file"
    rm -f $LOCK_FILE
}