#!/bin/ksh
# alt_o2b.sh
# This has not been tested by ShellCheck and runs under sh, bash, and ksh!

# 256 bytes of octal values from 000 to 377.
split_octal="000001002003004005006007010011012013014015016017
020021022023024025026027030031032033034035036037040041042043044045046047
050051052053054055056057060061062063064065066067070071072073074075076077
100101102103104105106107110111112113114115116117120121122123124125126127
130131132133134135136137140141142143144145146147150151152153154155156157
160161162163164165166167170171172173174175176177200201202203204205206207
210211212213214215216217220221222223224225226227230231232233234235236237
240241242243244245246247250251252253254255256257260261262263264265266267
270271272273274275276277300301302303304305306307310311312313314315316317
320321322323324325326327330331332333334335336337340341342343344345346347
350351352353354355356357360361362363364365366367370371372373374375376377"

binary()
{
	printf '%s\n' $split_octal | while read octal
	do
		# Obtain octal string length.
		length="${#octal}"
		# Subscript position starts at 1 NOT 0."
		position=1
		# 3 character octal value to be read.
		ooo="???"
		while [ "$position" -lt "$length" ]
		do
			# These two lines obtain the octal value.
			subtext1=${octal%"${octal#${ooo}}"}
			subtext2=${subtext1#"${subtext1%???}"}
			# Convert to pure binary.
			printf '%b' "\0$subtext2"
			# Increment values needed.
			position=$(( position + 3 ))
			ooo=$ooo'???'
		done
	done
}

binary > /tmp/binary2

# The line below is just for checking...
hexdump -C /tmp/binary2

exit 0