Chapter 6 - Script 1

#!/bin/sh
#
# 5/23/2017
#
echo "script1 - Linux Scripting Book"
while [ true ]
do
  date
  sleep 1d
done
echo "End of script1"
exit 0

If you run this on your system and wait a few days you will start to see the date slip a little. This is because the sleep command inserts a delay into the script, it does not mean that it is going to run the script at the same time every day.

Note

The following script shows this problem in a bit more detail. Note that this is an example of what not to do.

Chapter 6 - Script 2

#!/bin/sh
#
# 5/23/2017
#
echo "script2 - Linux Scripting Book"
while [ true ]
do
 # Run at 3 am
 date | grep -q 03:00:
 rc=$?
 if [ $rc -eq 0 ] ; then
  echo "Run commands here."
  date
 fi
 sleep 60                   # sleep 60 seconds
done
echo "End of script2"
exit 0

The first thing you will notice is that this script will run until it is either manually terminated with Ctrl + C or the kill command (or when the machine goes down for whatever reason). It is common for...