day 2 - original solution

02.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+set -eu
+
+# "oneline" versions follow each function
+
+part1() {
+	# 3,1 6,2 0,3 0,1 3,2 6,3 6,1 0,2 3,3
+	set -- 4 8 3 1 5 9 7 2 6
+	sort 02_input | uniq -c | awk '{print $1}' | while read l; do
+	printf "$l" | sed s/$/*$1+/ # if you go for the less magic-numbery version you can do sed "s/$/*(${1%,*}+${1#*,})/"
+		shift
+	done | sed s/+$/\\n/ | bc
+}
+# set -- 4 8 3 1 5 9 7 2 6; sort 02_input | uniq -c | awk '{print $1}' | while read l; do printf "$l" | sed s/$/*$1+/; shift; done | sed s/+$/\\n/ | bc
+
+part2() {
+	# 0,3 3,1 6,2 0,1 3,2 6,3 0,2 3,3 6,1
+	set -- 3 4 8 1 5 9 2 6 7
+	sort 02_input | uniq -c | awk '{print $1}' | while read l; do
+		printf "$l" | sed s/$/*$1+/ # same comment as before
+		shift
+	done | sed s/+$/\\n/ | bc
+}
+# set -- 3 4 8 1 5 9 2 6 7; sort 02_input | uniq -c | awk '{print $1}' | while read l; do printf "$l" | sed s/$/*$1+/; shift; done | sed s/+$/\\n/ | bc
+
+while getopts :12 OPT; do
+	case $OPT in
+		1) part1 && exit 0 ;;
+		2) part2 && exit 0 ;;
+		*) echo "bad option" 1>&2; exit 1 ;;
+	esac
+done

README.md

@@ -4,3 +4,4 @@ mainly going to be using shell + posix-defined utilities, probably
 
 ## Days
 1. awk (uses features exclusive to GNU's implementation, gawk)
+2. shell (completely POSIX-conforming implementation)