core-agent-linux/misc/upgrades-installed-check

#!/bin/bash

## `echo`s:
## * 'true' - if all upgrades have been installed
## * 'false' - if there are pending upgrades
## * nothing - if apt-get is currently locked
##
## Forwards the exit code of the package manager.

if [ -e /etc/system-release ]; then
   ## Fedora
   # shellcheck disable=SC2034
   yum_output="$(yum -q check-update 2>&1)"
   exit_code="$?"
   [ "$exit_code" -eq 100 ] && echo "false" && exit 0
   [ "$exit_code" -eq 0 ] && echo "true"
elif [ -e /etc/debian_version ]; then
   ## Debian
   set -e
   set -o pipefail
   # shellcheck disable=SC2034
   apt_get_update_output="$(apt-get -q update 2>&1)"
   apt_get_upgrade_output="$(LANG="C" apt-get -s upgrade 2>&1)"
   exit_code="$?"
   echo "$apt_get_upgrade_output" | awk "/^Inst/{ print $2 }" | [ "$(wc -L)" -eq 0 ] && echo "true" || echo "false"
elif [ -e /etc/arch-release ]; then
    ## Archlinux
    set -e
    set -o pipefail
    checkupdates_output="$(checkupdates 2>&1)"
    exit_code="$?"
    echo "$checkupdates_output" | { grep -F -- '->' || true; } | [ "$(wc -L)" -eq "0" ] && echo "true" || echo "false"
else
   echo "Check not implemented for this distribution" >&2
   exit 1
fi

exit "$exit_code"