This page contains some snippets I use as drafts for when doing bash scripts that I publish on the git page.

A function to check weather a service is running or not.

#!/usr/bin/env bash
 
usage() {
    printf "Usage: %s [options]\n" "$0"
    printf "  -n  hostname\n"
    printf "  -m  mariadb root password\n"
    printf "  -d  wordpress database name\n"
    printf "  -u  wordpress database user\n"
    printf "  -p  wordpress database password\n"
    printf "  -h  Show help\n\n"
    printf "Example:\n"
    printf "%s -n wp.something.xyz -m mariadbrootpwd -d wpdbname -u wpusername -p wpdbpassword\n\n" "$0"
}
 
# Parse CLI arguments with -m as second option
while getopts ":n:m:d:u:p:h" option; do
    case "$option" in
        n) hostname="${OPTARG,,}" ;; # lowercase
        m) mariadbrootpwd="$OPTARG" ;;
        d) wpdbname="$OPTARG" ;;
        u) wpdbuser="$OPTARG" ;;
        p) wpdbpass="$OPTARG" ;;
        h) usage; exit 0 ;;
        \?) printf "Invalid option: -%s\n" "$OPTARG"; usage; exit 1 ;;
        :) printf "Option -%s requires an argument.\n" "$OPTARG"; usage; exit 1 ;;
    esac
done
 
# === Required argument validation ===
validate_input() {
    local -a fields=(
        "hostname:hostname"
        "mariadb root password:mariadbrootpwd"
        "wordpress database name:wpdbname"
        "wordpress database user:wpdbuser"
        "wordpress database password:wpdbpass"
    )
 
    local missing=false
    for field in "${fields[@]}"; do
        local label="${field%%:*}"
        local varname="${field##*:}"
        local value="${!varname}"
 
        if [[ -z "$value" ]]; then
            printf "Error! %s is empty.\n" "$label"
            missing=true
        fi
    done
 
    if [[ $missing == true ]]; then
        printf "\n"
        usage
        exit 1
    fi
}
 
validate_input
 
# Print all variables
printf "\nhostname: %s\n" "$hostname"
printf "mariadb root password: %s\n" "$mariadbrootpwd"
printf "wordpress database name: %s\n" "$wpdbname"
printf "wordpress database user: %s\n" "$wpdbuser"
printf "wordpress database password: %s\n" "$wpdbpass"

#!/usr/bin/env bash
 
usage() {
    printf "Usage: %s [options]\n" "$0"
    printf "  -n  hostname\n"
    printf "  -m  mariadb root password\n"
    printf "  -p  gitea database password\n"
    printf "  -h  Show help\n\n"
    printf "Example:\n"
    printf "%s -n git.something.xyz -m mariadbrootpwd -p giteadbpassword\n\n" "$0"
}
 
# Initialize variables
hostname=""
mariadbrootpwd=""
giteadbpass=""
 
# Parse CLI arguments with -m as second option
while getopts ":n:m:p:h" option; do
    case "$option" in
        n) hostname="${OPTARG,,}" ;; # lowercase
        m) mariadbrootpwd="$OPTARG" ;;
        p) giteadbpass="$OPTARG" ;;
        h) usage; exit 0 ;;
        \?) printf "Invalid option: -%s\n" "$OPTARG"; usage; exit 1 ;;
        :) printf "Option -%s requires an argument.\n" "$OPTARG"; usage; exit 1 ;;
    esac
done
 
# === Required argument validation ===
validate_input() {
    local -a fields=(
        "hostname:hostname"
        "mariadb root password:mariadbrootpwd"
        "gitea database password:giteadbpass"
    )
 
    local missing=false
    for field in "${fields[@]}"; do
        local label="${field%%:*}"
        local varname="${field##*:}"
        local value="${!varname}"
 
        if [[ -z "$value" ]]; then
            printf "Error! %s is empty.\n" "$label"
            missing=true
        fi
    done
 
    if [[ $missing == true ]]; then
        printf "\n"
        usage
        exit 1
    fi
}
 
validate_input
 
# Print all variables
printf "\nhostname: %s\n" "$hostname"
printf "mariadb root password: %s\n" "$mariadbrootpwd"
printf "gitea database password: %s\n" "$giteadbpass"

First create a helper function that can parse variables and flags as well as dynamic usage.

#!/usr/bin/env bash
 
# ========================
# Print usage dynamically
# ========================
usage() {
    printf "Usage: %s [options]\n" "$0"
    for flag in "${flags[@]}"; do
        short="${flag%%:*}"
        rest="${flag#*:}"
        desc="${rest#*:}"
        desc="${desc%%:*}"
        printf "  -%s  %s\n" "$short" "$desc"
    done
    printf "  -h  Show help\n\n"
 
    # Example command
    printf "Example:\n"
    example="$0"
    for flag in "${flags[@]}"; do
        short="${flag%%:*}"
        sample="${flag##*:}"
        example+=" -$short $sample"
    done
    printf "%s\n\n" "$example"
}
 
# ========================
# Validate required flags
# ========================
validate_input() {
    local missing=false
    for flag in "${flags[@]}"; do
        short="${flag%%:*}"
        rest="${flag#*:}"
        var="${rest%%:*}"
        rest="${rest#*:}"
        desc="${rest%%:*}"
        rest="${rest#*:}"
        sample="${rest%%:*}"
        required="${rest##*:}"
 
        if [[ "$required" == "true" && -z "${!var}" ]]; then
            printf "Error! %s is empty.\n" "$desc"
            missing=true
        fi
    done
 
    if [[ $missing == true ]]; then
        printf "\n"
        usage
        exit 1
    fi
}

Then call it like this in your bash script.

#!/usr/bin/env bash
 
# ========================
# Flags array (required only)
# ========================
declare -a flags=(
    "n:hostname:hostname:wp.example.com:true"
    "m:mariadbrootpwd:MariaDB root password:rootpwd:true"
)
 
# ========================
# Source helpers
# ========================
source "$(dirname "$0")/helpers.sh"
 
# ========================
# Parse CLI arguments
# ========================
optstring="h"
for flag in "${flags[@]}"; do
    short="${flag%%:*}"
    optstring+="$short:"
done
 
while getopts "$optstring" option; do
    case "$option" in
        h) usage; exit 0 ;;
        *)
            for flag in "${flags[@]}"; do
                short="${flag%%:*}"
                rest="${flag#*:}"
                var="${rest%%:*}"
                if [[ "$option" == "$short" ]]; then
                    declare "$var"="$OPTARG"
                fi
            done
            ;;
        \?) printf "Invalid option: -%s\n" "$OPTARG"; usage; exit 1 ;;
        :)  printf "Option -%s requires an argument.\n" "$OPTARG"; usage; exit 1 ;;
    esac
done
 
# ========================
# Validate required flags
# ========================
validate_input
 
# ========================
# Print parsed variables
# ========================
echo "Hostname: $hostname"
echo "MariaDB root password: $mariadbrootpwd"