Installing command line tool if it's not in the PATH

Question

I have this bash function which I am trying to use to install a command line tool if it's not already in the PATH:

ncf(){

  if ! type -f ncf &> /dev/null || ! which ncf &> /dev/null; then

       echo "Installing NPM package '@oresoftware/ncf' globally...";

       npm i -s -g '@oresoftware/ncf' || {
         echo -e "Could not install NPM package '@oresoftware/ncf' globally." >&2
         echo -e "Please check your permissions to install global NPM packages." >&2
         return 1;
       }

  fi

  command ncf $@;
}

I have a couple of questions - is type -f ncf and which ncf redundant? Right now, I am checking to see if either of them exits with non-zero - if I either one does, I reinstall (at least that's what I think the code is doing).

My other question is - will &> work for bash versions older than 4, or other shells like sh, ksh, zsh, etc? Is there another construct I should use that's more cross platform than &>?

Answer 1

which is redundant with type, except when it does the wrong thing altogether. Don't use which ever (except in ksh or zsh). Don't use type -f in portable sh, either: that's a ksh/bash extension. Just use plain type. If you want to look for an external command despite the presence of a function by the same name, you can use (unset -f ncf; type ncf).

To redirect the output away, use >/dev/null 2>&1. This can be abbreviated to &>/dev/null in ksh, bash and zsh, but not in plain sh.

  if ! type -f ncf >/dev/null 2>/dev/null; then …