Bash-Template-Example.bash

Bash-Template-Example.bash

#!/usr/bin/env bash

# -*-  Coding: UTF-8  -*- #
# -*-  System: Linux  -*- #
# -*-  Usage:   *.*   -*- #

#
# General Bash Template
#

#
# Shellcheck Ignore List
#
# shellcheck disable=SC1073
# shellcheck disable=SC2120
# shellcheck disable=SC2071
# shellcheck disable=SC2086
#

#
# See Bash Set-Options Reference Below
#

set -o pipefail
set -o errexit
set -o xtrace

# Ensures a given amount of arguments is satisfied, otherwise logs a validation-related
# error, the expected number of arguments, and caller information. Usage is intended to
# be limited to other functions; calls to "validate" should never come from the global
# namespace.
#
# Arguments:
#   - (1): The total number of expected arguments.
#   - (2-n): The remaining arguments. Typically this value should be "${#}" without quoting.
#
# Example Usage:
#     function example() {
#         validate 2 ${#} || echo "Expected Argument(s) (1) (2) ..." > /dev/stderr
#         return 1
#     }
function validate() {
    [[ (( ${#FUNCNAME[*]} == 0 )) ]] && echo -e "Fatal Error - Cannot Call \"${FUNCNAME[0]}\" || \"${FUNCNAME[1]}\" From Global Namespace" > /dev/stderr && return 1

    echo "[Debug] (${FUNCNAME[1]}) Evaluating Input. Arguments-Count: (${#})" > /dev/stderr

    if ! [[ ${#} -eq 2 ]]; then
        echo "[Error] (${FUNCNAME[0]}) Invalid Arguments Received. Caller: \"${FUNCNAME[1]}\". Expected Total Arguments Required (1), and Total Caller Arguments (2)" > /dev/stderr
        return 1
    fi

    return 0
}

# Unsets authentication-related aws environment variables; caution usage
# in dynamic environments such as IMDSv2 capable systems.
function unset-aws-environment-variables() {
    unset AWS_ACCESS_KEY_ID
    unset AWS_SECRET_ACCESS_KEY
    unset AWS_SESSION_TOKEN

    unset AWS_PROFILE
    unset AWS_DEFAULT_PROFILE
}

# Creates an async worker. Requires a name argument (1).
#
# NOTE: Do not use a "-" or " " separated value for the (1) argument.
#
# A coprocess is executed asynchronously in a subshell, as if the command had been terminated
# with the ‘&’ control operator, with a two-way pipe established between the executing shell
# and the coprocess.
#
# Call "wait" to wait for all background jobs to complete.
#
# - https://www.gnu.org/software/bash/manual/html_node/Coprocesses.html
function worker() {
    validate 1 ${#} || echo "[Error] (${FUNCNAME[0]}) Invalid Arguments Received. Expected Worker-Name (1)" > /dev/stderr

    [[ -z "${1}" ]] && echo "[Error] (${FUNCNAME[0]}) Invalid Worker-Name (1). Caller: \"${FUNCNAME[1]}\"" > /dev/stderr && return 1
    
    declare name="${1}"
    
    # Start a named coprocess "${1}" running the "sleep" command following "echo".
    coproc "${name}" {
        echo "(${name}) Started ..."
        sleep 5
        echo "(${name}) Complete ..."
    }
}

function require() {
    for executable in "${@}"; do
        declare name="${executable}"

        if [[ -z $(command -v "${name}") ]]; then
            echo "[Error] (${FUNCNAME[0]}) Command Not Found. Target: \"${name}\"" > /dev/stderr
            return 1
        fi
    done
}

function main() {
    echo "[Log] (${FUNCNAME[0]}) ..." > /dev/stderr
    
    worker "testing"
    
    wait
}

require "jq" "kubectl" "go" "xcode-select" "git"

main

# 1.   set -o verbose     ::: Print shell input upon read.
# 2.   set -o allexport   ::: Export all variable(s) + function(s) to environment.
# 3.   set -o errexit     ::: Exit immediately upon pipeline'd failure.
# 4.   set -o monitor     ::: Output process-separated command(s).
# 5.   set -o privileged  ::: Ignore externals - ensures of pristine run environment.
# 6.   set -o xtrace      ::: Print a trace of simple commands.
# 7.   set -o braceexpand ::: Enable brace expansion. Enabled by default.
# 8.   set -o no-exec     ::: Bash syntax debugging; reads in commands but does not execute them.
# 9.   set -o pipefail    ::: Ensures the pipeline return value is that of the last command to exit.
# 10.  set -o history     ::: Enable the use of history for the given script.