bash-examples

index.sh

#!/usr/bin/env bash

SCRIPT_PATH="$(
  cd "$(dirname "$0")" || exit >/dev/null 2>&1
  pwd -P
)"#!/usr/bin/env bash

#################################
# Named arguments for base scripts
#################################
ARG_1='' ARG_2='' ARG_3='' ARG_4="4th arg"
eval "${@}"

ARG_3=${ARG_3:-"$(echo $PWD)"}

echo "ARG_1=${ARG_1}"
echo "ARG_2=${ARG_2}"
echo "ARG_3=${ARG_3}"
echo "ARG_4=${ARG_4}"

if [ "${ARG_1}" == "" ]; then
  echo 'ARG_1 == ""'
else
  echo 'ARG_1 != ""'
fi
if [ "${ARG_2}" == "" ]; then
  echo 'ARG_2 == ""'
else
  echo 'ARG_2 != ""'
fi
if [ "${ARG_3}" == "" ]; then
  echo 'ARG_3 == ""'
else
  echo 'ARG_3 != ""'
fi
if [ "${ARG_4}" == "" ]; then
  echo 'ARG_4 == ""'
else
  echo 'ARG_4 != ""'
fi
#################################

. lib.sh
addToStartOfTrapCommand "exit 1"

function help() {
  echo "Usage: cmd <ARG> [-h] [-r]"
  echo "Options:"
  echo "         -h    Show this help"
  echo "         -r    Remove the obsolete deployment after the new deployment takes its place (as opposed to only when a new deployment is triggered)"
}

if [ "$#" -ne 1 ]; then
  echo "Invalid number of arguments, $# given but 1 expected."
  echo ""
  help
  exit 1
fi

ARG=${1}

addToStartOfTrapCommand "exit 1"
export TOP_PID=$$

echo "Initial OPTIND: ${OPTIND}" # OPTIND contains the index of the next option to handle
# Prepend the list of valid options with ':' to disable the default error handling of invalid options.
# Options that themselves have arguments are followed by a ':'.
# The argument to an option is placed in the variable 'OPTARG'.
while getopts ":ab:ch" opt; do
  case ${opt} in
  a)
    echo "Option a"
    echo "OPTIND: ${OPTIND}"
    echo "'hostname':"
    hostname # the actual hostname
    echo "'echo hostname':"
    echo hostname # hostname
    echo "'echo \"\$(hostname)\"':"
    echo "$(hostname)" # the actual hostname
    echo "'getHostname':"
    getHostname # the actual hostname
    echo "'echo getHostname':"
    echo getHostname # getHostname
    echo "'echo \"\$(getHostname)\"':"
    echo "$(getHostname)" # the actual hostname
    echo "'HOSTNAME=\$(getHostname) && echo \${HOSTNAME}':"
    HOSTNAME=$(getHostname)
    echo ${HOSTNAME} # the actual hostname
    ;;
  b)
    target=$OPTARG
    echo "Option b: ${target}"
    echo "OPTIND: ${OPTIND}"
    ;;
  c)
    echo "Option c"
    echo "OPTIND: ${OPTIND}"
    ;;
  h)
    help
    echo "OPTIND: ${OPTIND}"
    exit 0
    ;;
  \?) # If an invalid option is provided, the option variable is assigned the value ?.
    echo "Invalid option: $OPTARG"
    echo "OPTIND: ${OPTIND}"
    help
    exit 1
    ;;
  :)
    echo "Invalid option: $OPTARG requires an argument"
    echo "OPTIND: ${OPTIND}"
    help
    exit 2
    ;;
  esac
done
# It is common practice to call the shift command at the end of your processing loop
# to remove options that have already been handled from $@.
shift $((OPTIND - 1))
echo "Final OPTIND: ${OPTIND}"
echo "ARG=${ARG}"
echo "Trap command: $(getCurrentTrapCommand "TERM")"
echo "This script path: ${SCRIPT_PATH}"


#
# Named arguments in Bash
#
# Synopsis: someFunction ARG_1="..." ARG_2="..." ARG_3="..." ARG_4="..."
#
function someFunction() {
  echo "${FUNCNAME[0]}" "$@"
  local ARG_1 ARG_2 ARG_3 ARG_4="4th arg"
  local "${@}"
  
  ARG_3=${ARG_3:-"$(echo $PWD)"}

  echo "ARG_1=${ARG_1}"
  echo "ARG_2=${ARG_2}"
  echo "ARG_3=${ARG_3}"
  echo "ARG_4=${ARG_4}"

  if [ "${ARG_1}" == "" ]; then
    echo 'ARG_1 == ""'
  else
    echo 'ARG_1 != ""'
  fi
  if [ "${ARG_2}" == "" ]; then
    echo 'ARG_2 == ""'
  else
    echo 'ARG_2 != ""'
  fi
  if [ "${ARG_3}" == "" ]; then
    echo 'ARG_3 == ""'
  else
    echo 'ARG_3 != ""'
  fi
  if [ "${ARG_4}" == "" ]; then
    echo 'ARG_4 == ""'
  else
    echo 'ARG_4 != ""'
  fi
}

someFunction ARG_1="1st arg"

lib.sh

#!/usr/bin/env bash

export TOP_PID=$$

#
# Synopsis: addToStartOfTrapCommand ${NEW_COMMAND} ${SIGNAL}
#
function addToStartOfTrapCommand() {
  local NEW_COMMAND
  NEW_COMMAND=${1}
  local SIGNAL
  SIGNAL=${2:-"TERM"}

  local CURRENT_TRAP_COMMAND
  CURRENT_TRAP_COMMAND=$(getCurrentTrapCommand "${SIGNAL}")

  trap "${NEW_COMMAND}; ${CURRENT_TRAP_COMMAND}" "${SIGNAL}"
}

#
# Synopsis: assertEquals "${CONTENT_A}" "${CONTENT_B}"
#
function assertEquals() {
  local CONTENT_A
  CONTENT_A=$(trim "${1}")
  local CONTENT_B
  CONTENT_B=$(trim "${2}")
  echo "assertEquals ${CONTENT_A} ${CONTENT_B}"

  if [ "${CONTENT_A}" != "${CONTENT_B}" ]; then
    echo "Assertion failed: '${CONTENT_A} != ${CONTENT_B}'"
    kill -s TERM ${TOP_PID} # This will exit the main script and trigger the trap
  fi
}

#
# Synopsis: getCurrentTrapCommand ${SIGNAL}
#
function getCurrentTrapCommand() {
  local SIGNAL
  SIGNAL=${2:-"TERM"}

  extract_trap_cmd() { printf '%s\n' "$3"; }
  eval "extract_trap_cmd $(trap -p "${SIGNAL}")"
}

#
# Synopsis: getHostname
#
function getHostname() {
  hostname # doing 'echo "$(hostname)"' would be doing a redundant echo
}