Some insane bash that might end up useful in the future

gistfile1.sh

#!/bin/bash
#
# Summary:
#   This script will set up your environment et al so you can run the Hive
#   Query Tool. This script is intended to be sourced, but can be run without
#   sourcing. The /path/to/perl argument(s) are optional.
#
# Usage:
#   source setup-hqt [/path/to/perl /path/to/other/perl ...]
#   setup-hqt [/path/to/perl /path/to/other/perl ...]
#
# More Info:
#   Use this script to find, fetch, build and install all the CPAN dependencies
#   for running the Hive Query Tool (HQT). This includes looking for the most
#   recent version of perl installed on your system and using it.
#
#   I have it do this because the HQT requires perl version 5.10.1 or greater
#   (which is actually already fairly old) and I have found that a lot of
#   systems around here don't have it.
#
#   So, this script will set everything up nice and orderly, if possible.
#
#   If you source this script in a bash shell, it will also set up your
#   environment so perl can find the installed dependencies.
#
#   If you wish/need, you can pass as arguments the path(s) to specific
#   perl binaries you want to try to use, and those will be checked instead
#   of the defaults.
#
#   If you don't have perl 5.10.1 or newer on your system, you'll need to find
#   a way to install one. If you have an RPM-based system, you should be able
#   to build an RPM for a more modern version by using another script in the
#   warehouse source tree:
#
#     $WHTOP/miscprojects/modern-perl/setup.sh
#
#   It will create an RPM that installs perl 5.16.1 under /opt/perl-5.16.1
#
#   Let's say you have that installed now...
#   You can then just source this script.
#
# @author: Stephen R. Scaffidi <sscaffidi@tripadvisor.com>
# @since: Oct. 2012
#


# get the version of the given perl binary
get-perlver () {
  "$1" -e 'print "$^V"' | sed 's/^v//'
}

# normalize the perl version so we can do a numeric comparison
normalize-ver () {
  local ver=$(echo "$1" | sed 's/[^0-9.]//g')
  echo "$ver" \
    | awk 'BEGIN{FS="."}{printf "%d", $1; for (i=2; i<=NF; i++) printf "%.3d", $i}'
}

# find the most recent perl on this system that is newer than the specified version
find-best-perl () {
  local need_nver=$( normalize-ver "$1" ); shift

  local best_nver=0  # track the highest numeric version found
  local best_ver=""  # ditto for the version-y version
  local best_perl="" # track the path to the perl with the highest version

  for found_perl in "$@"; do
    [[ ! -e "$found_perl" ]] && continue
    got_ver=$( get-perlver "$found_perl" )
    got_nver=$( normalize-ver "$got_ver" )
    [[ "$got_nver" < "$need_nver" ]] && continue
    if [[ "$got_nver" > "$best_nver" ]]; then
      best_perl="$found_perl"
      best_ver="$got_ver"
      best_nver="$got_nver"
    fi
  done
  cat <<END
$best_perl
$best_ver
END
}



###########################################################
# prep for script cleanup

# if anything goes wrong, this will restore the shell options
# changed in this script
cleanup-on-exit () {
  #echo "$?"
  set +e
  [[ "$nounset_status"  == "off" ]] && set +o nounset
  [[ "$pipefail_status" == "off" ]] && set +o pipefail
  [[ "$errexit_status"  == "on"  ]] && set -o errexit  # this one must be last!
  trap -- ERR
}


# get the state of the given shopt/set -o option (on or off)
shopt-status () {
  local _opt="$1"
  if shopt -q -o $_opt; then
    echo "on"
  else
    echo off
  fi
}


# if this script is being sourced, we'll want to record the current state
# of these shell options so we can change them back on exit
errexit_status=$(shopt-status "errexit")
pipefail_status=$(shopt-status "pipefail")
nounset_status=$(shopt-status "nounset")
trap "cleanup-on-exit" ERR

###########################################################
# Main script

set -e
set -o nounset
set -o pipefail

# determine if this script has been sourced or not
SELF_SOURCED="" && [[ "$0" == "bash" ]] && SELF_SOURCED=1

# here are some common places to look for perl binaries
POSSIBLE_PERLS=( `which -a perl` /{opt,usr/local}/perl*/bin/perl )

# if the user specified which perl(s) they want to try, then just use those
[[ $# -gt 0 ]] && POSSIBLE_PERLS=( "$@" )

# now, find the best available perl
FOUND_PERL=( $(find-best-perl "5.10.1" "${POSSIBLE_PERLS[@]}") "" "")
BEST_PERL="${FOUND_PERL[0]}"
BEST_VER="${FOUND_PERL[1]}"

# if a suitable perl could not be found...
if [[ "$BEST_PERL" == "" ]]; then
  echo 1>&2 "Could not locate a new enough version of perl."
  echo 1>&2 "Please upgrade, or contact sscaffidi@tripadvisor.com for help."
  # terminate differently depending on how we were called.
  set +e; [[ -n "$SELF_SOURCED" ]] && return 1; exit 1
fi

echo "Found perl $BEST_VER at $BEST_PERL"

# these vars aren't required by perl or the app, but they may come in handy
PERL_VER="$BEST_VER"
PERL_NAME="perl-$BEST_VER"
PERL_BINDIR="$( dirname "$BEST_PERL")"

# should be the dir where this script lives. the code below will get
# the correct path even if the script is sourced.
APP_ROOT=$(cd `dirname "${BASH_SOURCE[0]}"` && pwd)

# the external dependencies for this code will be installed here
APP_EXTLIB="$APP_ROOT/extlib"

# make sure your path finds the new perl first
# TODO: make this smarter so we don't keep adding to the path like crazy.
#  perhaps use the value in PERL_LOCAL_LIB_ROOT to clean out old LL paths.
export PATH="$PERL_BINDIR:$PATH"

# in case local::lib is already in use, clear up those env vars
unset PERL_LOCAL_LIB_DIR PERL_LOCAL_LIB_ROOT PERL_MB_OPT PERL_MM_OPT PERL5LIB


# setup the symlink to make it easier to deal with
# different versions of perl
echo "Setting up extlib dir"
mkdir -p "$APP_ROOT/.extlib/$PERL_NAME"
rm -f "$APP_EXTLIB"
ln -sf ".extlib/$PERL_NAME" "$APP_EXTLIB"

# if creating a new extlib, record some info about the build.
# if a different user or different perl is running this, record that, too.
# don't bother adding anything if the user or perl or host are all the same.
BUILD_INFO="$USER@$(hostname)	$BEST_PERL	$PERL_VER"
BUILD_INFO_FILE="$APP_EXTLIB/extlib-built-by.txt"
[[ -e "$BUILD_INFO_FILE" ]] && grep -q -F "$BUILD_INFO" "$BUILD_INFO_FILE"
[[ $? -ne 0 ]] && echo "[$(date)]	$BUILD_INFO" >> "$BUILD_INFO_FILE"

# install cpanm and local::lib so we can install those deps cleanly
echo "Checking dependency toolchain"
[[ -x "$APP_EXTLIB/bin/cpanm" ]] ||
  curl --silent --show-error --location http://cpanmin.us \
  | perl - --quiet --local-lib="$APP_EXTLIB" App::cpanminus local::lib

# now setup the environment so perl knows to look there
# and so cpan/cpanm knows to install deps there.
echo "Setting perl env for libs"
eval $(perl -I"$APP_EXTLIB/lib/perl5" -Mlocal::lib="$APP_EXTLIB")

# now instruct cpanm to install all the dependencies
# declared in the Makefile.PL
echo "Making sure all dependencies are installed"
cpanm --quiet --installdeps . \
&& echo "Done!"

[[ -n "$SELF_SOURCED" ]] || cat <<END
Note that you must *source* this script so your shell picks up the vars that
will tell perl how to find the stuff in extlib!
END

# this is important to end the script!
cleanup-on-exit