Reading files

Now let's look again at the method the backup scripts in the last chapter used to get the value from a file:

Chapter 7 - Script 2

#!/bin/sh
#
# 6/2/2017
#
echo "Chapter 7 - Script 2"

FN=filenum1.txt              # input/output filename
MAXFILES=5                   # maximum number before going back to 1

if [ ! -f $FN ] ; then
  echo 1 > $FN               # create the file if it does not exist
fi

echo -n "Contents of $FN: "
cat $FN                      # display the contents

count=`cat $FN`              # put the output of cat into variable count
echo "Initial value of count from $FN: $count"

let count++
if [ $count -gt $MAXFILES ] ; then
 count=1
fi

echo "New value of count: $count"
echo $count > $FN

echo -n "New contents of $FN: "
cat $FN

echo "End of script2"
exit 0

Here is the screenshot for Script 2:

We start by setting the FN variable to the name of the file (filenum1.txt). It is displayed by the cat command and then the contents of the file are assigned to the...