rhel-upchk

#!/usr/bin/env bash
################################################################################
# rhel-upchk - uses either dnf or yum to check for updates (depending on your
# version of RHEL-based distro) and sends an email if there are any available.
# Requires a working 'mail' command (you may need to install the
# 'mailx' package or similar).
#
# Dependencies: mail, mailx, etc.
#
# Version 3
# Matthew Malensek <matt@malensek.net>
################################################################################

cmd="dnf"
command -v dnf &> /dev/null || cmd="yum"

if [[ ${#} -lt 1 ]]; then
    echo "Usage: $(basename ${0}) email@address.com"
    exit 1
fi

mail_to="${1}"

# get the list of new updates, and remove any blank lines
update_list=$(${cmd} --debuglevel=0 --errorlevel=0 check-update | sed '/^$/d')
num_updates=$(wc -l <<< "${update_list}")

subject="$num_updates updates available for $(hostname)"

if [[ $num_updates -gt 0 && $update_list != "" ]]; then
    echo "$update_list" | mail -s "$subject" $mail_to
fi