Easy way in Bash to check that a binary is installed.

magic_jq_task.sh

#!/bin/bash

# Exit on the first command that returns a nonzero code.
set -e

# Function that checks if a given executable is on the path. If it isn't, prints an install message and exits.
# Usage: check_binary EXECUTABLE_NAME INSTALL_MESSAGE
check_binary() {
  if ! which "$1" > /dev/null; then
    # Using a subshell to redirect output to stderr. It's cleaner this way and will play nice with other redirects.
    # https://stackoverflow.com/a/23550347/225905
    ( >&2 echo "$2" )
    # Exit with a nonzero code so that the caller knows the script failed.
    exit 1
  fi
}

check_binary "jq" "$(cat <<EOF
You will need jq to run this script.
Install it using your package manager. E.g. for homebrew:
brew install jq
EOF
)"

# a dumb command that uses jq in order to provide a SSCCE snippet
# http://sscce.org/
jq -r ".message" <<EOF
{"message": "hello from jq!"}
EOF