#!/bin/bash
# wf.sh: Crude word frequency analysis on a text file.


# Check for input file on command line.
ARGS=1
E_BADARGS=65
E_NOFILE=66

if [ $# -ne "$ARGS" ]  # Correct number of arguments passed to script?
then
  echo "Usage: `basename $0` filename"
  exit $E_BADARGS
fi

if [ ! -f "$1" ]       # Check if file exists.
then
  echo "File \"$1\" does not exist."
  exit $E_NOFILE
fi



########################################################
# main ()
sed -e 's/\.//g'  -e 's/ /\
/g' "$1" | tr 'A-Z' 'a-z' | sort | uniq -c | sort -nr
#                           =========================
#                            Frequency of occurrence

#  Filter out periods and
#+ change space between words to linefeed,
#+ then shift characters to lowercase, and
#+ finally prefix occurrence count and sort numerically.
########################################################

# Exercises:
# ---------
# 1) Add 'sed' commands to filter out other punctuation, such as commas.
# 2) Modify to also filter out multiple spaces and other whitespace.
# 3) Add a secondary sort key, so that instances of equal occurrence
#+   are sorted alphabetically.

exit 0