autohwsched.sh: a simple script to generate class schedule list for each day in a month in a CSV format

autohwsched.sh

#!/bin/bash

## autohwsched.sh: a simple script to generate class schedule list for each day in a
## month in a CSV format. It is useful for tracking at a glance whether and how
## consistently daily work is being completed.

## usage: ./autoshwsched.sh month > file.csv

## NOTE: This script assumes a five day class schedule and reads from "classes.csv" in
## the same directory by default (can be configured below). It does not add any
## formatting data, and currently does not remove class lists for partial weeks at the
## beginning and end of the month. Some manual editing is required on the output file.

# Copyright (C) 2020 Christian Arnold 
# 
# Redistribution and use in source and binary forms, with or without modification, are
# permitted provided that the following conditions are met:
# 
# 1. Redistributions of source code must retain the above copyright notice, this list
# of conditions and the following disclaimer.
# 
# 2. Redistributions in binary form must reproduce the above copyright notice, this list
# of conditions and the following disclaimer in the documentation and/or other materials
# provided with the distribution.
# 
# 3. Neither the name of the copyright holder nor the names of its contributors may be
# used to endorse or promote products derived from this software without specific prior
# written permission.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
# SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
# DAMAGE.

MONTH=$1 # first argument (required); later arguments are ignored

# if first argument is not given, give usage and exit
[ -z "$MONTH" ] && echo "usage: $0 month > file.csv" >&2 && exit 1

# class schedule to read from
FILE=classes.csv

# check whether the file actually exists or not
[ ! -x $FILE ] && echo "$0: need to create $FILE file to generate calendar from" >&2 && exit 2

# Our iterator which we will use later
i=0

# Read the output from `cal' and cycle through each line one by one for processing
cal -m $MONTH | while read -r LINE; do

	# break if the line is empty because that could cause problems
	[ -z "$LINE" ] && break

	# increment the iterator (it's probably better to use a for loop for this...)
	i=$((i+1))

	# Trim the trailing whitespace of the first line and skip
	# everything else. Our read command will ignore leading whitespace.
	[ $i -eq 1 ] && sed -e 's/[[:space:]]*$//' <<< "$LINE" && continue
	
	# The second line contains only names of days so we can simply echo the line
	# we already edited and continue
	[ $i -eq 2 ] && sed -e 's/[[:space:]]*$//' <<< "$LINE" | tr " " "," && continue
	
	# The third line is where the actual calendar starts. Rather than try to count
	# the whitespace, we are going to count the number of days in the first week
	# (it is usually less than 7) so we simply subtract that number from 7 and add
	# that number of commas to the beginning so that it is aligned properly in
	# Excel or whatever

	if [ $i -eq 3 ]; then
		DAYS_OF_FIRST_WEEK=`wc -w <<< "$LINE"`
		#echo debug: DAYS_OF_FIRST_WEEK=$DAYS_OF_FIRST_WEEK >&2
		
		if [ $DAYS_OF_FIRST_WEEK -lt 7 ]; then
			EXTRA_FIELDS=$((7-DAYS_OF_FIRST_WEEK))
			#echo debug: EXTRA_FIELDS=$EXTRA_FIELDS >&2
		
			for j in `seq $EXTRA_FIELDS`; do
				LINE=",$LINE"
			done
		fi
		#echo debug: line = $LINE >&2
	fi

	# Remove trailing whitespace, condense double spaces into a single space,
	# and replace spaces with commas
	sed -e 's/[[:space:]]*$//' <<< "$LINE" | tr -s '[:space:]' | tr " " ","

	# After we have parsed the line of date numbers, we are simply going to be
	# pasting in the csv file defined earlier. We could delete the items we don't
	# have days for (like in the first and last week of the month) but that's way
	# easier to do manually after the fact than try to code for it here...

	# We are also going to add an extra field to the beginning because
	# weekend classes aren't a thing. So this requires a bit of editing. But note
	# that we are doing no other editing to the file, so we are assuming that the
	# file is in proper csv format.
	while read -r line; do
		echo ",$line"
	done < $FILE
done