#!/bin/sh
# vim: set syn=sh et ai cin sw=2 ts=2 tw=0:
VER=0.2
LICENCE=GPLv2+
AUTHOR="Cyrille Pontvieux <jrd@enialis.net>"
REAL_UNAME=/bin/uname
BAK_UNAME=/bin/uname.orig
fail() {
  echo "$@" >&2
  exit 1
}
check_root() {
  if [ $(id -u) -ne 0 ]; then
    fail "You should be root to install or uninstall fake uname."
  fi
}
version() {
  echo "Version: $VER"
  echo "Licence: $LICENCE"
  echo "Author: $AUTHOR"
  exit 0
}
is_installed() {
  [ -e $BAK_UNAME ] && file $REAL_UNAME | grep -q 'shell script'
}
# $1 = kernel name
# $2 = hostname
# $3 = kernel release
# $4 = kernel version
# $5 = machine type name
# $6 = processor
# $7 = platform
# $8 = OS
install() {
  if is_installed; then
    fail "fake-uname already installed, please use reinstall."
  else
    mv $REAL_UNAME $BAK_UNAME
    cat <<EOF > $REAL_UNAME && chmod +x $REAL_UNAME
#!/bin/sh
S="$1"
N="$2"
R="$3"
V="$4"
M="$5"
P="$6"
I="$7"
O="$8"
[ "\$P" = "unknown" ] && P=""
[ "\$I" = "unknown" ] && I=""
U=""
add() {
  [ -n "\$U" ] && U="\$U \$1" || U="\$1"
}
while [ -n "\$1" ]; do
  case "\$1" in
    -s|--kernel-name)
      add "\$S"
      ;;
    -n|--nodename)
      add "\$N"
      ;;
    -r|--kernel-release)
      add "\$R"
      ;;
    -v|--kernel-version)
      add "\$V"
      ;;
    -m|--machine)
      add "\$M"
      ;;
    -p|--processor)
      add "\$P"
      ;;
    -i|--hardware-platform)
      add "\$I"
      ;;
    -o|--operating-system)
      add "\$O"
      ;;
    -a|--all)
      U="\$S \$N \$R \$V \$M \$P \$I \$O"
      ;;
    --verion)
      $BAK_UNAME --version
      exit 0
      ;;
    --help)
      $BAK_UNAME --help
      exit 0
      ;;
  esac
  shift
done
[ -z "\$U" ] && U="\$S"
echo \$U
EOF
  fi
}
uninstall() {
  if is_installed; then
    mv $BAK_UNAME $REAL_UNAME
  else
    fail "fake_uname already uninstalled."
  fi
}
usage() {
  cat <<'EOF'
Usage: fake-uname [CMD] [OPTION]
CMD could be:
  install: install the fake uname with the following overriding options.
  reinstall: same as install but could be used if an already fake-uname is installed.
  uninstall: uninstall the fake uname. No option needed.
OPTION could be one or more of the following
  -s kernel-name
  -n nodename
  -r kernel-release
  -v kernel-version
  -m machine
  -p processor
  -i hardware-platform
  -o operating-system
EOF
  exit 0
}
CMD=''
if [ -n "$1" ]; then
  case "$1" in
    -v|--version)
      version
      ;;
    -h|--help)
      usage
      ;;
    install|reinstall|uninstall)
      CMD=$1
      shift
      ;;
    *)
      fail "The command $1 is not supported."
      ;;
  esac
else
  usage
fi
check_root
if [ "$CMD" = "reinstall" ] || [ "$CMD" = "uninstall" ]; then
  uninstall
fi
if [ "$CMD" = "reinstall" ] || [ "$CMD" = "install" ]; then
  S="$($REAL_UNAME -s)"
  N="$($REAL_UNAME -n)"
  R="$($REAL_UNAME -r)"
  V="$($REAL_UNAME -v)"
  M="$($REAL_UNAME -m)"
  P="$($REAL_UNAME -p)"
  I="$($REAL_UNAME -i)"
  O="$($REAL_UNAME -o)"
  while [ -n "$1" ]; do
    case "$1" in
      -v|--version)
        version
        ;;
      -h|--help)
        usage
        ;;
      -s)
        shift
        S="$1"
        ;;
      -n)
        shift
        N="$1"
        ;;
      -r)
        shift
        R="$1"
        ;;
      -v)
        shift
        V="$1"
        ;;
      -m)
        shift
        M="$1"
        ;;
      -p)
        shift
        P="$1"
        ;;
      -i)
        shift
        I="$1"
        ;;
      -o)
        shift
        O="$1"
        ;;
      *)
        fail "The option $1 is not supported."
        ;;
    esac
    shift
  done
  install "$S" "$N" "$R" "$V" "$M" "$P" "$I" "$O"
fi
uname -a