Example scaffolding and helpers for bash scripts

common_util.sh

#!/bin/bash

###############################################################################
# Helpers                                                                     #
###############################################################################

# `is_set` accepts a function and checks if a variable is set.
# The function it accepts should generate a string for an error
# message
is_set() {
  local msg_func="$1"
  for i in "${@:2}"; do
    eval echo \${$i:?"$($msg_func $i)"} > /dev/null
  done
}

env_not_set_msg() {
  local var="$1"
  echo "Environment Variable $var is not set (required)."
}

param_not_set_msg() {
  local var="$1"
  echo "Command line param $var is not set (required)."
}

# Method to check if a program is installed and exit if not.
programs_exist() {
  local msg_func="$1"
  for i in "${@:2}"; do
    eval command -v $i > /dev/null 2>&1 || { $msg_func $i; exit 1; }
  done
}

program_not_accessible() {
  local var="$1"
  echo "Program $var is not installed or accessible (required)." >&2
}

is_empty() {
  local var="$1"
  [[ -z "$var" ]]
}

###############################################################################
# AWS :: DyanmoDB                                                             #
###############################################################################

default_aws_region() {
  echo "us-east-1"
}

delete_dynamo_db_table_io() {

  local aws_key="$1"
  local aws_secret="$2"
  local aws_region="$3"
  local table_name="$4"

  AWS_ACCESS_KEY_ID="$aws_key" AWS_SECRET_ACCESS_KEY="$aws_secret" aws \
    dynamodb \
    delete-table \
    --table-name "$table_name" \
    --region "$aws_region"
}

dynamodb_delete.sh

#!/bin/bash

readonly PROGNAME=$(basename $0)
readonly PROGDIR=$(readlink -m $(dirname $0))
readonly ARGS="$@"

# bring in common utilities and variables
source "$PROGDIR/common_util.sh"

usage() {
	cat <<- EOF
	usage: $PROGNAME
	
	options
	
	Delete a DynamoDB table
	
	OPTIONS:
	-k --aws-key          AWS key
	-r --aws-region       AWS region
	-s --aws-secret       AWS secret
	-n --table-name       Name of the DynamoDB table to delete
	-h --help             help!
	EOF
}

cmdLine() {

  local aws_region_tmp=""

  local arg=
  for arg
  do
    local delim=""
    case "$arg" in
      --aws-key)    args="${args}-k ";;
      --aws-region) args="${args}-r ";;
      --aws-secret) args="${args}-s ";;
      --table-name) args="${args}-n ";;
      --help)       args="${args}-h ";;
      *) [[ "${arg:0:1}" == "-" ]] || delim="\""
          args="${args}${delim}${arg}${delim} ";;
    esac
  done

  eval set -- $args

  while getopts "hk:n:r:s:" OPTION
  do
    case $OPTION in
      h)
        usage
        exit 0
        ;;
      k)
        readonly AWS_KEY=$OPTARG
        ;;
      n)
        readonly TABLE_NAME=$OPTARG
        ;;
      r)
        aws_region_tmp=$OPTARG
        ;;
      s)
        readonly AWS_SECRET=$OPTARG
        ;;
    esac
  done

  # Set AWS_REGION to a default if it doesn't exist
  readonly AWS_REGION=${aws_region_tmp:=$(default_aws_region)}

  return 0

}

# Required command line params
required_cmd_line_params_io() {

  is_set param_not_set_msg \
         "AWS_KEY" \
         "AWS_REGION" \
         "AWS_SECRET" \
         "TABLE_NAME"
}

# Required programs
required_programs_io() {
  programs_exist program_not_accessible "aws"
}

main() {
  cmdLine $ARGS
  required_cmd_line_params_io
  required_programs_io

  delete_dynamo_db_table_io "$AWS_KEY" \
                            "$AWS_SECRET" \
                            "$AWS_REGION" \
                            "$TABLE_NAME"
}

main