#!/bin/sh -u
#   $0 [ filename ]
# Concatenate the given file name over and over into another file.
# Prompt for a file name if there are no command line arguments.
# -IAN! idallen@ncf.ca

export PATH=/bin:/usr/bin
umask 022

# The name of our output file.
#
outputfile="bar"
 
# Validate the correct number of arguments on the command line.
#
if [ "$#" -ge 2 ] ; then
	echo 1>&2 "$0: Expecting zero or one argument, found $# ($*)"
	exit 1	# return a bad exit code
fi

# If there are no arguments, get one from standard input.
# Echo the name being processed back to the user.
#
if [ "$#" -eq 0 ] ; then
	echo 1>&2 "Please enter a file name:"
	read filename
else
	filename="$1"
fi
echo "I am processing '$filename'."

# Verify that the user's input is 1) a file, 2) readable, 3) not empty.
#
if [ ! -f "$filename" ]; then
	echo 1>&2 "$0: '$filename' is not a file"
	exit 1	# return a bad exit code
fi
if [ ! -r "$filename" ]; then
	echo 1>&2 "$0: '$filename' is not readable"
	exit 1	# return a bad exit code
fi
if [ ! -s "$filename" ]; then
	echo 1>&2 "$0: '$filename' has no size (is empty)"
	exit 1	# return a bad exit code
fi

# Empty the output file.
# Loop, appending, while the number of lines is less than the constant.
# We *must* use the syntax <"$outputfile" to redirect stdin to "wc".
#
>"$outputfile"
while [ $(wc -l <"$outputfile") -lt 100 ]; do
	linecount=$(wc -l <"$outputfile")
	echo "The number of lines in $outputfile is $linecount"
	cat "$filename" >>"$outputfile" || exit $? # exit if cat has an error
done