Bash CLI skeleton + debug reader

bash_cli_skeleton.sh

#!/usr/bin/env bash

#/ Sample command to perform update and query it's status
#/
#/ Usage: <SELF_NAME> [-h|--help] <command>
#/
#/ Available commands:
#/     one      - perform some update, idempotent
#/                usage: <SELF_NAME> one <arg1> [arg2]
#/     two      - query status of update
#/                usage: <SELF_NAME> two <arg1>
#/
#/ Environment variables:
#/     DEBUG=1  - troubleshoot logic using config.debug file
#/     FORCE=1  - enforce action, disables idempotence

set -eu -o pipefail -o errtrace -o functrace
test "${BASH_VERSINFO[0]}" -lt 4 || shopt -s inherit_errexit nullglob compat"${BASH_COMPAT=42}"

# === prereq === #

: "${DEBUG:=}"
: "${FORCE:=}"
readonly DEBUG FORCE

IS_SOURCED=$(test "${BASH_SOURCE[0]}" == "${0}" || echo 1)
SELF_FILE=$(\grep -E '^(\.|\/)' <<< "${BASH_SOURCE[0]}" || echo "./${BASH_SOURCE[0]}")
WORK_DIR=$(\pwd -P)
DEBUG_FILE="${WORK_DIR}/${SELF_FILE##*/}.dbg"
readonly IS_SOURCED SELF_FILE WORK_DIR DEBUG_FILE

# === func === #

main() {
    test -z "${DEBUG}" || {
        enable_debug "${DEBUG_FILE}"
        : "Sourced=${IS_SOURCED:-0}"
        : "WorkDir=${WORK_DIR}"
        stderr "# sending debug stream into ${DEBUG_FILE##*/} file in current directory ..."
    }

    ! \grep -Eq "(^|\s)--help|-h(\s|$)" <<< "$*" || usage

    check_requirements

    declare cmd="${1:-}"
    shift || :

    case "${cmd,,}" in
    one)    cmd_one "$@" ;;
    two)    cmd_two "$@" ;;
    *)      usage "invalid command specified" ;;
    esac
}

cmd_one() {
    declare arg1="${1:-}"
    declare arg2="${2:-default2}"

    test -n "${arg1}" || fatal "arg1 is empty"

    echo "running sub command: one(${arg1}, ${arg2})"
}

cmd_two() {
    declare arg1="${1:-}"

    test -n "${arg1}" || fatal "arg1 is empty"

    echo "running sub command: two(${arg1})"
}

enable_debug() {
    declare file="$1"

    exec 19> "${file}"
    export BASH_XTRACEFD=19

    shopt -s extdebug

    declare -g DEBUG_START_MS
    DEBUG_START_MS=$(unix_milliseconds)
    readonly DEBUG_START_MS

    export PS4='+ [$(( $(unix_milliseconds) - $DEBUG_START_MS ))ms] at ${BASH_SOURCE[0]}:${LINENO} in ${FUNCNAME[0]:-main}${FUNCNAME[0]:+()} [pid:${BASHPID},sub:${BASH_SUBSHELL},uid:${EUID}] '
    set -x

    : "OS=${OSTYPE}"
    : "Bash=${BASH_VERSINFO[0]}.${BASH_VERSINFO[1]}.${BASH_VERSINFO[2]}"
    : "BashOpts=${BASHOPTS}"
}

check_requirements() {
    printf '4.1\n%s\n' "${BASH_VERSION}" | \sort -CV || fatal "bash 4.1+ is required, got ${BASH_VERSION} ..."

    for cmd in jq perl sed; do
        command -v "${cmd}" &>/dev/null || fatal "command '${cmd}' is missing"
    done

    declare version
    version=$(\jq --version 2>&1 | \awk -F'[ -]' 'OFS="-" {$1="";gsub("^-+","",$0)}1')
    printf '1.6\n%s' "${version}" | \sort -CV || fatal "\jq 1.6+ is required, got ${version} ..."
}

fatal() {
    printf -- "Error: %s\n" "${@}" >&2
    exit 1
}

stderr() {
    printf -- "%s\n" "${@}" >&2
}

unix_milliseconds() {
    test "${BASH_VERSINFO[0]}" -lt 5 || {
        date +%s%3N
        return
    }

    echo $(( "${EPOCHREALTIME/./}" / 1000 ))
}

usage() {
    declare err_msg="${1:-}"

    \grep '^#/' "${SELF_FILE}" | \cut -c4- | \sed -e "s/<SELF_NAME>/${SELF_FILE##*/}/"

    test -n "${err_msg}" || exit 0

    echo
    fatal "${err_msg}"
}

readlinkf() {
    \perl -MCwd -l -e 'print Cwd::abs_path shift' "$1"
}

indent() {
    \sed -e 's/^/  /'
}

# === main === #

test -n "${IS_SOURCED}" || {
    main "$@"
    exit 0
}

bash_debug_reader.sh

#!/usr/bin/env bash

set -e

fatal() {
    printf -- "Error: %s\n" "${@}" >&2
    exit 1
}

declare file="${1:-}"
declare line prev

test -n "${file}" || fatal 'provide filename'
test -f "${file}" || fatal 'file is missing or not readable'

while IFS= read -r line; do
    if test "${line:0:1}" != "+"; then
        # 2nd+ multiline
        echo "${line}"
        continue
    fi

    declare -i t1=0
    declare -i t2=0

    if test "${prev}" == ""; then
        prev="${line}"
        continue
    fi

    t1=$(echo "${prev}" | sed -r -e 's,.*^\++\s+\[([0-9]+)ms\].*,\1,')
    t2=$(echo "${line}" | sed -r -e 's,.*^\++\s+\[([0-9]+)ms\].*,\1,')
    elapsed=$((t2-t1))

    echo "${prev}" | sed -r -e "s/\[([0-9]+ms)\]/[\1+${elapsed}ms]/"

    prev="${line}"
done < "$file"

if test "${prev}" != ""; then
    echo "${prev}" | sed -r -e "s/\[([0-9]+ms)\]/[\1+0ms]/"
fi