shell script utilities, complete with unit test

utils.sh

#!/bin/bash

# What directory are we in?
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

# TeamCity messages
teamcity () { 
  echo "##teamcity[message text='$*']"
}

# Parse a filename, see http://stackoverflow.com/revisions/1403489/2
parse_filename () {
  fullpath=$1
  part=$2
  
  # Strip longest match of */ from start
  filename="${fullpath##*/}"                      
  # Substring from 0 thru pos of filename
  dir="${fullpath:0:${#fullpath} - ${#filename}}" 
  # Strip shortest match of . plus at least one non-dot char from end
  base="${filename%.[^.]*}"                       
  # Substring from len of base thru end
  ext="${filename:${#base} + 1}"                  
  # If we have an extension and no base, it's really the base
  if [[ -z "$base" && -n "$ext" ]]; then          
      base=".$ext"
      ext=""
  fi

  case "$part" in
    dir)
      echo "$dir"
      ;;

    base)
      echo "$base"
      ;;

    ext)
      echo "$ext"
      ;;

    *)
      echo -e "$fullpath:\n\tdir  = \"$dir\"\n\tbase = \"$base\"\n\text  = \"$ext\""
  esac
}

# Get directory from a pathname
directory () {
  echo $(parse_filename $1 dir)
}

# Get a file's basename (filename without extension), given its full pathname
base () {
  echo $(parse_filename $1 base)
}

# Get a file's extension from its full pathname
extension () {
  echo $(parse_filename $1 ext)
}


# Returns a filename with a default extension appended, if there wasn't one
with_default_extension () {
  FILENAME=$1
  DEFAULT_EXT=$2
  EXT=$(extension $FILENAME)
  if [ "$EXT" = "" ]; then
    FILENAME=$FILENAME$DEFAULT_EXT
  fi
  echo $FILENAME
}


# To test, run this with `./utils.sh --test-utils`
if [[ "$1" == "--test-utils" ]]; then 

  # Generic test function. Usage:
  #
  #   test_function <expected> \
  #     <function> <args...>
  #
  # (I put `<function> <args...>` on the second line for readability)

  test_function () {
    EXPECTED=$1
    FUNCTION=$2
    shift; shift
    RESULT=$($FUNCTION $*)
    if [ "$RESULT" != "$EXPECTED" ]; then
      echo "Failed: function $FUNCTION, actual '$RESULT', expected '$EXPECTED'"
      exit 1
    fi    
  }

  test_function snap \
    extension foo.snap
  test_function "" \
    extension .bash_profile
  test_function "" \
    extension no-extension-file

  test_function foo.snap \
    with_default_extension foo.snap 
  test_function .bash_profile.zumbulus \
    with_default_extension .bash_profile .zumbulus
  test_function no-extension-file.zumbulus \
    with_default_extension no-extension-file .zumbulus
  echo 'Passed'
fi