A C interpreter as a shell script. Note, this is every bit as stupid as it sounds. The summer of 1995 was not a great time for good engineering decisions for me.

c2.sh

#!/bin/sh
# C interpreter in sh.  Wow.
# Logic: we parse files, or arguments, or stdin.
# We see if we have exactly one argument that looks like a file.  If so,
# we parse it.  Otherwise, we look for arguments.  Otherwise, we work on
# stdin.

ANSI="Y"
VERBOSE="N"
INCLUDES="stdio.h stdlib.h ctype.h"

tmp=/tmp/.$$.c
>$tmp

trap 'rm -f $tmp ${tmp}2 ${tmp}3 /tmp/.$$.out' 2 3

eat() {
	echo $* >> $tmp
}

while getopts ai:v i
do
	case $i in
	a)	ANSI="N";;
	i)	INCLUDES="$INCLUDES $OPTARG";;
	v)	VERBOSE="Y";;
	\?)	echo >&2 "usage: c2 [-i header] [file] | [lines]"
		break;;
	esac
done
shift `expr $OPTIND - 1`

case $# in
0)	grep -v '^#!' > $tmp
	;;
1)	if [ -r "$1" ]
	then	grep -v '^#!' $1 > $tmp
	else	eat "$1"
	fi
	;;
*)	for i
	do	eat "$i"
	done
	;;
esac

for i in $INCLUDES
do
	echo "#include <$i>" >> ${tmp}2
done

if grep "main[ 	]*(" $tmp >/dev/null 2>&1
then	cat ${tmp}2 $tmp > ${tmp}3
	mv ${tmp}3 $tmp
else	case "$ANSI" in
	"Y")	echo "int main(int argc, char *argv[]) {" >> ${tmp}2;;
	"N")	echo "int main(argc, argv) char *argv[]; {" >> ${tmp}2;;
	esac
	cat ${tmp}2 $tmp > ${tmp}3
	mv ${tmp}3 $tmp
	echo "; return 0;}" >> $tmp
fi

rm -f ${tmp}2

[ -z "$CC" ] && case "$ANSI" in "Y") CC=lcc;; "N") CC=cc;; esac

[ "$VERBOSE" = "Y" ] && echo "Source:" && cat $tmp

if	${CC:-cc} $tmp -o /tmp/.$$.out
then	/tmp/.$$.out
	save="$?"
else	save=1
fi

rm -f $tmp /tmp/.$$.out

exit $save