Brainf**k interpreter in POSIX shell

bf-intp.sh

#!/bin/sh

while IFS= read L; do
  T=$T$L
done < "$1"

L=0
while [ "$T" ]; do
  case $T in
    +*) export "C$L"=0 L=$((L+1));;
    -*) export "C$L"=1 L=$((L+1));;
   \>*) export "C$L"=2 L=$((L+1));;
   \<*) export "C$L"=3 L=$((L+1));;
    .*) export "C$L"=4 L=$((L+1));;
    ,*) export "C$L"=5 L=$((L+1));;
   \[*) export "C$L"=6 L=$((L+1));;
   \]*) export "C$L"=7 L=$((L+1));;
  esac
  T=${T#?}
done

P=0
while [ $P != 16384 ]; do
    export "A$P"=0
    P=$((P+1))
done

N=0
P=0
while [ $N != $L ]; do
  case $((C$N)) in
    0) export "A$P"=$((A$P+1));;
    1) export "A$P"=$((A$P-1));;
    2) P=$((P+1));;
    3) P=$((P-1));;
    4) printf "$(printf '\\%o' $((A$P)))";;
    5) stty -icanon
       D=$(dd bs=1 count=1 2>/dev/null)
       export "A$P"=$(printf '%d' \'$D)
       stty icanon;;
    6) case $((A$P)) in
         0) D=1
            while [ $D != 0 ]; do
              N=$((N+1))
              case $((C$N)) in
                6) D=$((D+1));;
                7) D=$((D-1));;
              esac
            done;;
         *) ;;
       esac;;
    7) case $((A$P)) in
         0) ;;
         *) D=1
            while [ $D != 0 ]; do
              N=$((N-1))
              case $((C$N)) in
                6) D=$((D-1));;
                7) D=$((D+1));;
              esac
            done;;
       esac;;
  esac
  N=$((N+1))
done

An example in Debian GNU/Linux 11 x86_64 with dash 0.5.11:

$ cat primes.bf
>++++[<++++++++>-]>++++++++[<++++++>-]<++.<.>+.<.>++.<.>++.<.>------..<.>.++.<.>--.++++++.<.>------.>+++[<+++>-]<-.<.>-------.+.<.>-.+++++++.<.>------.--.<.>++.++++.<.>---.---.<.>+++.-.<.>+.+++.<.>--.--.<.>++.++++.<.>---.-----.<.>+++++.+.<.>.------.<.>++++++.----.<.>++++.++.<.>-.-----.<.>+++++.+.<.>.--.>++++++++++.
$ dash bf-intp.sh primes.bf
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97