This is my .bash_profile. Please consider it a useful reference. Not guaranteed to be completely current or completely quick. I use long-lived shell sessions, so a 2-second load time doesn't bother me.

.bash_profile

#!/usr/bin/env bash

# Set up handy aliases, simple environment tweaks, and other pleasantries.
# While shooting yourself in the foot is always a possibility, you may as well
# do it in comfort and occasionally style.

# Owner: Ryan McKern

# Start counting how long it takes to source this profile
__begin="$(date +"%s")"

# Keep so, so, so much history
export HISTFILESIZE=''
export HISTSIZE=''
# Don't keep duplicates in history; keep more history!
export HISTCONTROL="ignorespace:erasedups"
# Ignore backgrounding, mutt, quitting, and clearing
export HISTIGNORE="&:mutt:[bf]g:exit:clear"
# Append every command to history
PROMPT_COMMAND="history -a; history -c; history -r; ${PROMPT_COMMAND}"

# Avoid overwriting history
shopt -s histappend
# Smart handling of multi-line commands
shopt -s cmdhist
# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# Set the default umask to group-writable
umask 0022

# This is the minimum viable Bash version.
# Anything older than this will be used as the cut-off point.
__minimum_viable='3'

# Don't do anything for non-interactive shells
[[ -z "${PS1}"  ]] && return

# Set the old Gentoo default prompt if this isn't a dumb terminal
if [ "${TERM}" != 'dumb' ] && [ -n "${BASH}" ]; then
  if [ "${UID}" -eq "0" ] ; then
    # Privileged prompt, ending in #
    export PS1='\[\033[01;31m\]\h \[\033[01;34m\]\W # \[\033[00m\]'
  else
    # Unprivileged prompt, ending in $
    export PS1='\[\033[01;32m\]\u@\h \[\033[01;34m\]\W \$ \[\033[00m\]'
  fi
fi

# Are we using something greater than bash 2?
if (( ! "${BASH_VERSINFO[0]}" > "${__minimum_viable}" )); then
  echo "You're using an old version of Bash (${BASH_VERSION}). Sourcing .bash_profile will now halt." >&2
  return
fi

# define pathmunge, and use that for $PATH manipulation.
# pathmunge is normally provided in RHEL environments,
# and this is copied almost wholesale from their implementation.
pathmunge(){
  if ! echo "${PATH}" | grep -q "(^|:)${1}(\$|:)"; then
    [[ -d ${1} ]] || return
    if [ "${2}" = "after" ] ; then
      PATH="${PATH}:${1}"
    else
      PATH="${1}:${PATH}"
    fi
  fi
}

# Use this as short-hand to determine if a function
# is already implemented
function_defined(){
  if [[ ${1:-UNDEFINED} == 'UNDEFINED' ]]; then
    echo 'no function name specified' >&2
    return 2
  fi

  type "${1}" | head -n1 | grep -q 'is a function'
  retval=$?

  if [[ ${retval} == 0 ]]; then
    echo "true"
    return
  fi

  echo 'false'
  return 1
}

# At least try to make a good faith effort to determine if
# core utilities are their GNU or BSD variants
is_gnu(){
  # false if utility doesn't exist
  if ! which "${1}" > /dev/null 2>&1; then
    echo "false"
    return 1
  fi

  # true if utility exists and says it's GNU
  if "${1}" --version 2>&1 | grep -qi 'gnu'; then
    echo "true"
    return 0
  fi

  # false otherwise
  echo "false"
  return 1
}


# Source system-wide bash completion if it exists
[ -f '/etc/bash_completion' ] && source '/etc/bash_completion'


# This is an OS Specific switchyard: figure out what
# environment this is being run in, and configure it
# accordingly. Currently supports Solaris, OS X & Linux.
case "$(uname -s)" in
  # All linux configuration goes here
  Linux*)

    ## Have we got local bin paths? Prepend them.
    pathmunge /usr/local/sbin before
    pathmunge /usr/local/bin before

    # If we're using a RHEL-based distro, let's make looking for packages easier
    [ -f /etc/redhat-release ] && {
      rpmgrep(){
        rpm -qa | grep -i "${1}" | sort
      }
    }
  ;;

  # This is for the 3 or 4 solaris machines you might encounter
  SunOS*)
    # Seriously. I want to know.
    echo -e "\n\nWhere did you find a Solaris machine?\n\n"

    # Don't even bother with whatever path we've inherited. Build a new one.
    # Make sure that pathmunge is a function, not some weird whoknowswhat
    if type pathmunge | grep -q function; then
      pathmunge /bin before
      pathmunge /usr/bin before
      pathmunge /sbin after
      pathmunge /usr/sbin after
      pathmunge /usr/xpg4/bin before
      pathmunge /usr/local/bin before
      pathmunge /usr/local/sbin before
      pathmunge /opt/SUNWspro/bin before
      pathmunge /usr/ccs/bin before
      pathmunge /hub/SunOS/5.8/sun4u/apps/openssh-3.0p1/bin before
    fi

    # Again, let's at least look for bash completion
    [ -f '/usr/local/etc/bash_completion' ] && source '/usr/local/etc/bash_completion'

    # If the TERM isn't something sane, lie
    [[ ${TERM} =~ xterm-color ]] && export TERM=xterm
    # Make sure that CC points to a GCC if possible. That'll matter.
    command -v gcc >/dev/null 2>&1 && export CC=gcc
  ;;

  # This is for OS X. It's old, but it supports Homebrew
  # and old Developer Tools installations. It also understands
  # where Oracle installed MySQL by default.
  Darwin*)

    # Here's some paths that might exist. If they do, we wants them so badly!
    pathmunge /opt/local/sbin before
    pathmunge /opt/local/bin before
    pathmunge /usr/local/sbin before
    pathmunge /usr/local/bin before
    pathmunge /Developer/Tools after
    pathmunge /usr/local/mysql/bin after

    # Gotta clear that DNS cache somehow, right?
    flushdns(){
      sudo killall -HUP mDNSResponder
      return $?
    }

    # View man pages as PDF files
    pman(){
      command man -t "${@}" | open -g -f -a /Applications/Preview.app
      return $?
    }

    # Don't bother with `locate` or any findutils nonsense. Just use Spotlight.
    alias locate='mdfind -name'
  ;;
esac

###### Aliases & Functions: make your life easier ######

# find dead symlinks in the current directory or $1
deadlinks(){
  local __path="${1:-./}"
  find -L "${__path}" -type l -print
}

# sorted list of the contents of PWD or $1
alias howbig='du -Lh --max-depth=1'

# General aliases
alias ..='cd ..'
alias mkdir='mkdir -p'
alias du='du -h'
alias df='df -Th'

# generic psgrep
alias psgrep="ps auxww | grep -i"
# generic history grep
alias hgrep="history | grep -i"
# Rehash the path using the principle of least surprise
alias rehash="hash -r"

# Load everything in ~/.profile.d if it exists
__counter=0
__profiles="${HOME}/.profile.d"
if [ -d "${__profiles}" ]; then
  shopt -s nullglob

  # Pre files
  for __file in "${__profiles}"/pre_*.sh; do
    source "${__file}"
    __counter=$((__counter + 1))
  done

  # Anything not tagged pre or post
  for __file in "${__profiles}"/*.sh; do
    [[ "$(basename "${__file}")" =~ ^pre_|post_ ]] && continue
    source "${__file}"
    __counter=$((__counter + 1))
  done

  # Post files
  for __file in "${__profiles}"/post_*.sh; do
    source "${__file}"
    __counter=$((__counter + 1))
  done
  shopt -u nullglob
fi

__dim='\e[2m'
__normal='\e[22m'

# Wrap up counting the seconds since this started
__end="$(date +"%s")"

# Dump to screen and let me get on with my life!
printf "%bProfile loaded in %s seconds%b\n" "${__dim}" "$((__end-__begin))" "${__normal}"
printf "%b> Loaded %s sub-profiles from %s%b\n" "${__dim}" "${__counter}" "${__profiles}" "${__normal}"
unset __counter __profiles

example.txt

Last login: Sat Sep  9 02:18:21 on ttys000
Profile loaded in 3 seconds
> Loaded 19 sub-profiles from /Users/ryan/.profile.d
ryan@bender ~ $