un bout de coquillage

Quelles commande(s) allons-nous (re)découvrir aujourd'hui ?
Voici pour la première partie.

#!/bin/sh
# 1ドル: input file
for c in 'grep' 'sed' 'sort' 'test'
do
 if ! command -v "$c" >/dev/null
 then
 echo "Error: command '$c' not found" >&2
 exit 3
 fi
done
if test -z "1ドル"
then
 echo "Please call me with an input file..." >&2
 exit 1
fi
if grep -Eqsv '^[a-zA-Z]+$' "1ドル"
then
 echo "Found invalid line, check the file!" >&2
 exit 2
fi
_if="1ドル"
_fc=$( mktemp ) # first compartiment
_sc=$( mktemp ) # second compartiment
_si='' # shared items
while IFS= read -r line <&3
do
 printf '%s' "$line" | cut -c -$(( ${#line}/2 )) |
 sed 's/./&\n/g' | sort -uo "$_fc"
 printf '%s' "$line" | cut -c $(( ${#line}/2 + 1 ))- |
 sed 's/./&\n/g' | sort -uo "$_sc"
 _si="$_si$( comm -12 "$_fc" "$_sc" )"
done 3<"$_if"
rm "$_fc" "$_sc"
#echo "$_si" | cat -vet
_ps=0 # priority sum
_ac=0 # ASCII code
for character in $( echo "$_si" )
do
 _ac=$( printf '%d' "'$character" )
 case "$character" in
 [a-z]) # a is 97 but should translate to 1
 _ps=$(( _ps + _ac - 96 )) ;;
 [A-Z]) # A is 65 but should translate to 27
 _ps=$(( _ps + _ac - 38 )) ;;
 *) echo "$character=$_ac=??" >&2 ;;
 esac
done
echo "$_ps"

La grande difficulté est que l'écriture suivante (à laquelle j'ai initialement pensée) n'est pas POSIX (c'est une facilité de (ba|k|z)sh mais pas reconnue dans ash par exemple)

_fc='' # first compartiment
_sc='' # second compartiment
_si='' # shared items
while IFS= read -r line
do
 _fc="$( printf '%s' "$line" | cut -c -$(( ${#line}/2 )) |
 sed 's/./&\n/g' | sort )"
 _sc="$( printf '%s' "$line" | cut -c $(( ${#line}/2 + 1 ))- |
 sed 's/./&\n/g' | sort )"
 _si="$_si$( comm -12 <( printf '%s' "$_fc" ) <( printf '%s' "$_sc" ) )"
done <"$_if"

Pas grave, on troque l'utilisation de RAM (dont la machine où j'ai testé manque un peu) contre des fichiers (j'ai des E/S sur disque assez performantes pour que ce ne soit pas problématique.)

"It is seldom that liberty of any kind is lost all at once." ― David Hume