Bash Script Template

template.sh

#! /bin/bash

COLOR_NC='\033[0m' # No Color
COLOR_LGREEN='\033[1;32m'
COLOR_GRAY='\033[1;30m'
COLOR_LGRAY='\033[0;37m'
COLOR_RED='\033[0;31m'

logv() {
  [[ -z "$VERBOSE" ]] && return 0;

  >&2 echo -e "${COLOR_GRAY}$@${COLOR_NC}" || true
}

logerr() {
  >&2 echo -e "${COLOR_RED}$@${COLOR_NC}"
}

log() {
  >&2 echo -e "${COLOR_LGREEN}$@${COLOR_NC}"
}

panic() {
  logerr "$@"
  exit -1;
}

curlv() {
  execv curl "$@"
}

execv() {
  logv "$@"
  "$@"
}

# Write your usage
usage() {
  echo "$0 [command] [arg1]
  Do something interesting
  
  command:  This does something.
    arg1: This is the parameter
       defaults to blahblah...
  " && \
  grep " .)\ #" $0; exit 0;
}


parse_args() {
  OPTIND=1
  local s=$(echo "$1" | tr '[:upper:]' '[:lower:]')
  case "$s" in
    # add other subcommands here
    help|h|\?)
      export subcommand=$s
      OPTIND=2
      ;;
  esac

  # Parse flags
  while getopts ":hv" arg; do
    case $arg in
    v) # Verbose mode - extra output
      VERBOSE=true
      FLAGS="$FLAGS -v"
      ;;
    h | *) # Display help.
      usage
      exit 0
      ;;
    esac
  done

  export OPTIND
}

parse_args $@ && shift $(($OPTIND - 1))
  # If they put args before the command like 'bin/contentful -s 1xab migrate -y', try parsing again
[[ -z "$subcommand" ]] && parse_args $@ && shift $(($OPTIND - 1))


require_env() {
  # Test for existence of a command
  command -v jq >/dev/null 2>&1 || logerr "I require 'jq' but it's not installed."
  
  if [[ -z "${SOME_API_KEY}" ]]; then
    load_rc_file
    logv "setting SOME_API_KEY"
    export SOME_API_KEY=$(jq -r '.SOME_API_KEY' ~/.whateverrc)
  fi

  [[ ! -z "$SOME_API_KEY" ]] || panic "Could not load SOME_API_KEY"
}

load_rc_file() {
  if [ -f ~/.whateverrc ]; then
    if [[ ! -z $(jq -r '.SOME_API_KEY' ~/.whateverrc) ]]; then
      return 0
    fi
  fi

  log "Please paste in your API key:"
  read -s password
  [[ -z $password ]] && panic "No api key supplied!"
   
  (cat ~/.whateverrc 2>/dev/null || echo "{}") | jq ". + {SOME_API_KEY: \"$password\"}" > ~/.whateverrc.tmp
  mv ~/.whateverrc.tmp ~/.whateverrc
  return 0
}

do_it() {

  logv "Verbose to stderr"
  logvv "Extra Verbose to stderr"
  log "Regular Logging to stdout"

  # Curl an API and get the ID element, logging the request to stderr when '-v' given
  curlv -s https://some.api/entry.json | jq -r .id

  # Run a command and log to stderr the command that was run together with result
  logv $(execv npm install typescript)

  # Run this same script line by line over a list of inputs
  if [[ "$LINES" == "all" ]]; then
    LINES=`...` # get the list
    LAST=''
    while read -r line; do
      $0 $FLAGS $line $LAST
      [[ $? -ne 0 ]] && exit -1
    done <<< "${LINES}"
    exit 0
  fi

  # Read a body from a file, or from stdin, or as command line args
  if [[ -z "$1" ]]; then
    BODY=$(cat)
  elif [[ -f $1 ]]; then
    BODY=$(<$1)
  else
    BODY="$@"
  fi

  # Complex print formatting
  FORMAT="%12s $P %7d $P ${COLOR_LGREEN}%+9d${COLOR_NC} $P ${COLOR_RED}%+9d${COLOR_NC} $P %8d $P ${COLOR_LGREEN}%+6d ${COLOR_RED}%+6d${COLOR_NC} %7s \n"
  printf $FORMAT $key $commits[$key] $additions[$key] $del $activity $spec_additions[$key] $spec_del "($specs_activity)"

  logerr "Failure! (stderr)" && exit -1
}


set -e

case $subcommand in
  do_it)
    require_env
    do_it "$@"
    ;;
  help|h|\?)
    usage
    ;;
  version|v)
    echo "$VERSION"
    ;;
  *)
    logerr "Unknown command: '$1'"
    usage
    exit -1
    ;;
esac