msgbox делает то что вам нужно для cron
Вот мой crontab
# Edit this file to introduce tasks to be run by cron.
#
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
#
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
#
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
#
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
#
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h dom mon dow command
# min 0-59
# hor 0-23
# day 1-31
# mou 1-12
# day 0-6 (0=sun)
# * any value
# cron variables
# var
# @reboot Запуск при загрузке
# @yearly 1 time year 0 0 1 1 *
# @annually 1 time year
# @monthly 1 time mon 0 0 1 * *
# @weekly 1 time sem 0 0 * * 0
# @daily 1 time day 0 0 * * *
# @midnight (00:00)
# @hourly every hor 0 * * * *
# @hourly every hor 0 * * * *
# ----------------------------------------------------------------------
SHELL=/bin/bash
MAILTO=username
# ----------------------------------------------------------------------
# Добавление файла расписания:
# crontab имя_файла_расписания /home/home/crontab
# ----------------------------------------------------------------------
# Первый канал
#15 16 * * * DISPLAY=:0 gdialog --msgbox "1 Хочу знать" 25 20 > /dev/null
# ----
# HTB
30 15 * * * DISPLAY=:0 gdialog --msgbox "НТВ ЧП" 25 20 > /dev/null
40 17 * * * DISPLAY=:0 gdialog --msgbox "НТВ Говорим и показываем" 25 20 > /dev/null
30 18 * * * DISPLAY=:0 gdialog --msgbox "НТВ ЧП" 25 20 > /dev/null
# Россия
50 13 * * * DISPLAY=:0 gdialog --msgbox "Россия Дежурная часть" 25 20 > /dev/null
# Ц
10 15 * * * DISPLAY=:0 gdialog --msgbox "Ц Петровка 38" 25 20 > /dev/null
#14 12 * * * DISPLAY=:0 gdialog --msgbox "НТВ Следствие вели" 25 20 > /dev/null