Template for writing a bash script with fancy debugging.

hello-bash.sh

#! /usr/bin/env bash
#
# Template for writing a bash script with fancy debugging.
#
# Not yet tested at depth. Only basic handling of:
#  - running from stdin i.e. |bash
#  - sub-functions
#  - sourcing of other files
#
# Pythonic asssumptions:
#  - you have a main() worker
#  - it can be sourced without running main()
#  - other functions can be run by passing as args
#

DEBUG=yep

main() {
    gethere  # sets $HERE

    echo 'Hello world!'

    source "$HERE/sourceme.sh"
    donky

    foo
}

# ----------------------------------------------------------------------

gethere() {
    local here="${BASH_SOURCE[0]%/*}"
    [[ $here != "${BASH_SOURCE[0]}" ]] || here=.
    HERE=$(cd -P -- "$here" && pwd)
}

foo() {
    source "$HERE/sourceme.sh"
    bar
}

bar() {
    source "$HERE/sourceme.sh"
}

# ======================================================================
# shellcheck disable=SC2128
if [ -z "$BASH_VERSINFO" ] || [[ ${BASH_VERSINFO[0]} -lt 4 ]]
then
    echo "ERROR: Only tested on Bourne-Again SHell v4/v5."
    exit 1
fi >&2

# poor man's __main__
return 2>/dev/null ||:

if [ "$(type -t "$1")" = "function" ]
then
    func="$1"
    shift 1
    "$func" "$@"
    exit 0
fi

set -o errtrace
set -o errexit
set -o nounset
set -o pipefail

if [[ "${DEBUG:-}" ]]
then
    PS4func() {
        local normal="\033[0m"
        #local red="\033[0;31m"
        #local green="\033[0;32m"
        local yellow="\033[0;33m"
        #local blue="\033[0;34m"
        #local magenta="\033[0;35m"
        local cyan="\033[0;36m"

        local i caller_idx=-1
        # walk the call stack to see if we are sourced and from where
        if [[ ${#BASH_SOURCE[@]} -gt 2 ]]
        then
            for (( i=2; i<${#BASH_SOURCE[@]}; i++ ))
            do
                if [[ ${BASH_SOURCE[1]} != "${BASH_SOURCE[i]}" ]]
                then
                    caller_idx=$i
                    break
                fi
            done
        fi

        local src func=''
        local caller deep
        if [[ $caller_idx -ne -1 ]]
        then  # we're in a sourced script

            if [[ ${BASH_SOURCE[0]} == main ]]
            then caller='<stdin>'
            else caller="${BASH_SOURCE[0]##*/}"
            fi

            src="$caller:${BASH_LINENO[caller_idx-1]}${cyan}source->$yellow${BASH_SOURCE[1]##*/}:${BASH_LINENO[0]}"

            if [[ ${FUNCNAME[-2]} == main && ${FUNCNAME[-1]} == main ]]
            then deep=$((${#FUNCNAME[@]}-5))
            else deep=$((${#FUNCNAME[@]}-4))
            fi

        elif [[ ${BASH_SOURCE[0]} == main ]]
        then  # reading from standard input instead of a script file
            src="<stdin>:${BASH_LINENO[0]}"
            deep=$((${#FUNCNAME[@]}-1))

        else  # a normal script file
            src="${BASH_SOURCE[0]##*/}:${BASH_LINENO[0]}"
            deep=$((${#FUNCNAME[@]}-2))
        fi

        if (( deep >= 1 ))
        then
            if [[ ${FUNCNAME[1]} != source ]]
            then func+="${FUNCNAME[1]}()"
            fi
        fi

#        local lines="${BASH_LINENO[@]}"
#        local sources="${BASH_SOURCE[@]##*/}"
#        local funcs="${FUNCNAME[@]}"
#        printf "${red}sources(%d): %s\nlines(%d): %s | funcs(%d): %s|%b" \
#            "${#BASH_SOURCE[@]}" "$sources" \
#            "${#BASH_LINENO[@]}" "$lines" \
#            "${#FUNCNAME[@]}" "$funcs" \
#            "$yellow$src$cyan$func$normal "
# run the above to debug your stacks
        printf "%b" "$yellow$src$cyan$func$normal "
    }
    PS4='\r$(PS4func)'
    set -o xtrace
fi

main "$@"
exit 0

sourceme.sh

main() {
    echo 'Hello from sourced.'
    donky
}

donky() {
    echo 'Hee haw.'
    balls
}

balls() {
    echo 'Dafuq!'
}

main