A useful bash function that checks for command availability; if not present abort with an error message.

#!/usr/bin/env bash

# support function to check for command dependencies
function check_deps
{
  DEPENDENCIES="curl git"
  deps_ok=YES

  for dep in $DEPENDENCIES
  do
    if ! $(which $dep &>/dev/null); then
      echo "* ${dep} not found!"
      deps_ok=NO
    fi
  done

  if [[ $deps_ok == NO ]]; then
    echo "Please install the missing dependencies and try again."
    echo "Aborting!"
    exit 1
  else
    return 0
  fi
}

check_deps