#!/bin/sh
set -e

TMP=$(umask 077; mktemp -d)
echo >&2 " tmp $TMP"
Die() {
 trap - EXIT
 rm -rf $TMP
 exit ${1:-$e}
}; trap Die HUP EXIT #INT

pause() {(
 echo >&2 -n "Continue? ..."
 read -sn1 REPLY
 echo >&2
)}
confirm() {(
 echo >&2 -n "$@ [y/n] "
 read -n1 REPLY
 echo >&2
 case $REPLY in
 y|Y) :
  ;;
 n|N) exit 1
  ;;
 *) confirm "again"
  ;;
 esac
)}

I=0
if [ -n "$1" ]; then
 echo >&2 " [thanks] for the file (om nom)."
 I=1
 C="$1"
 shift 1
fi

case $I in
0)
 echo >&2 "[+] Building/testing internal program now; lucky!"
 echo >&2 " You should really be more cautious..."
 echo >&2 " (hehe) -wait for the potential virus..."
 echo >&2 " ... you believe too much in what you read,"
 echo >&2 "  never can you be fully certain of anything..."
 cat >"$TMP/t.c" <<%EOF
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>

void
input() {
 struct stat stdin_stat;
 fstat(0,&stdin_stat);
 if (S_ISCHR(stdin_stat.st_mode)) return; /*interactive*/
 /*if (S_ISFIFO(stdin_stat.st_mode)) return; /*pipe mode*/

 char sti[256];
 while (1) {
  if (fgets(sti, sizeof sti, stdin) ==NULL) break; /**/
  printf("%s",sti);
 }
}

void
files() {
 FILE *f;
 f=fopen("____file","w");
 mkdir("____dir",0755);
}

void
main() {
 input();
 files();
 exit(0);
}
%EOF
 ;;
1)
 cat "$C" >"$TMP/t.c"
 ;;
esac

cd $TMP ||{ echo '[error: cannot enter directory] '"$TMP"; Die 1; }>&2

cc -o exe t.c ||:

case $I in
0)
 echo 'ABCDEF' |./exe ||:
 ;;
1)
 ./exe "$@" ||:
 ;;
esac
e=$?

(confirm "program removes tmp. (CTRL-C to abort)")

Die $e