Dan's Shell Script Template

script.sh

#!/bin/bash

#####
# Dan's shell script template v1.0
# Public Domain. Use and abuse to your heart's delight

# Set some basic shell parameters. Let's list some useful ones:
#  a - Auto export all variables created. This shares them with sub processes without the 'export' built-in
#  e - Die on errors
#  u - Die if unset variables are used
#  x - Trace (print) commands as they are executed
#  o - Set Bash options:
#        pipefail - only consider a pipe failed if the last expression fails
#        posix - Change behavior to match posix when there are differences
set -eo pipefail

# if verbose is set, then we set "Print all commands before execution"
if [[ -n ${VERBOSE+x} ]]; then
  set -x
fi

# Set Defaults. The syntax is VAR_NAME=${VAR_NAME:-default_value}
#default to us-east-1
export AWS_REGION=${AWS_REGION:-us-east-1}

# a few colors to be cool
GREEN="\033[32m"
REG="\033[0m"
RED="\033[31m"
YELLOW="\033[33m"
WHITE="\033[1;37m"
SUBDUED="\033[90m"

if [[ "$TERM" != *color* ]]; then
    # no pretty colors if this is a non-color terminal
    GREEN=""
    REG=""
    RED=""
    YELLOW=""
    WHITE=""
    SUBDUED=""
fi

# A few helper variables
ME=$(basename $0)
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

error(){
    echo -e "[${RED}ERROR${REG}] $1" 1>&2 
}

warn(){
    echo -e "[${YELLOW}WARNING${REG}] $1" 1>&2 
}

usage(){
        echo -e "${WHITE}$ME${REG} - what I do
    
    ${SUBDUED}Usage:${REG} $ME explain
        ${WHITE}parameter${REG}\texplaination
    Notes:
        Any notes
    "
}

# Handle simple options
while getopts ":v" o; do
    case "${o}" in
        v)
            set -x
            VERBOSE=1
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND-1))

# Handle positional variables
# ensure we have the required number of parameters
if [[ "$#" -lt 2 ]]; then
    usage
    exit 2
fi 

PARAM="$1"
shift

# Check that all our sub-commands exist
for command in jq; do
    command -v "${command}" 2>&1 > /dev/null || \
    { error "${WHITE}The '${command}' command is not found${REG}. Please install it and ensure it's in the PATH" ; ALLGOOD=bad; };
done

# Check if we had any missing commands
if [[ "${ALLGOOD}" == "bad" ]]; then
    error "Errors encounterd. Please see above and try again."
    exit 1
fi