redhat-rpm-config/brp-mangle-shebangs

#!/bin/sh -eu

# If using normal root, avoid changing anything.
if [ -z "$RPM_BUILD_ROOT" -o "$RPM_BUILD_ROOT" = "/" ]; then
  exit 0
fi

cd "$RPM_BUILD_ROOT"

trim() {
  printf '%s' "$*"
}

fail=0
for f in $(find -executable -type f | xargs --no-run-if-empty file -N --mime-type | grep -Po "^\K.+(?=: text/)"); do

  ts=$(stat -c %y "$f")

  read orig_shebang < "$f" || :
  shebang=$(trim $(echo "$orig_shebang" | grep -Po "#!\K.*" || echo))
  if [ -z "$shebang" ]; then
    echo >&2 "*** WARNING: $f is executable but has empty or no shebang, removing executable bit"
    chmod -x "$f"
    touch -d "$ts" "$f"
    continue
  elif [ -n "${shebang##/*}" ]; then
    echo >&2 "*** ERROR: $f has shebang which doesn't start with '/' ($shebang)"
    fail=1
    continue
  fi

  if ! { echo "$shebang" | grep -q -P "^/(?:usr/)?(?:bin|sbin)/"; }; then
    continue
  fi

  # Replace "special" env shebang:
  # /whatsoever/env /whatever/foo → /whatever/foo
  shebang=$(echo "$shebang" | sed -r -e 's@^(.+)/env /(.+)$@/\2@')
  # /whatsoever/env foo → /whatsoever/foo
  shebang=$(echo "$shebang" | sed -r -e 's@^(.+/)env (.+)$@\1\2@')

  # Replace ambiguous python with python2
  py_shebang=$(echo "$shebang" | sed -r -e 's@/usr/bin/python(\s|$)@/usr/bin/python2\1@')

  if [ "$shebang" != "$py_shebang" ]; then
    sed -i -e "1c #!$py_shebang" "$f"
    echo >&2 "*** WARNING: mangling shebang in $f from $orig_shebang to #!$py_shebang. This will become an ERROR, fix it manually!"
  elif [ "#!$shebang" != "$orig_shebang" ]; then
    sed -i -e "1c #!$shebang" "$f"
    echo "mangling shebang in $f from $orig_shebang to #!$shebang"
  fi

  touch -d "$ts" "$f"
done

exit $fail