Shell Programming and Scripting

#!/bin/sh
mailcontents=mailbody
while read line
do
    if [ ! -f $line ]; then
        echo "The file $line doesn't exist. Continuing with the next file..." >> $mailcontents
        echo "============" >> $mailcontents 
        continue
    else
        last_mod_time=$(perl -MFile::stat -e "print stat('$line')->mtime") # this line checks the log's last modification time and converts it to Unix's epoch
        last_24_hours=$(perl -e 'print time-86400') # this line returns the epoch for the current timestamp minus 24 hours

        if [ $last_mod_time -lt $last_24_hours ]; then
            echo "Log $line has NOT been updated in the last 24 hours" >> $mailcontents
        else
            echo "Log $line was updated during the last 24 hours" >> $mailcontents
        fi
    
        tail -100 $line > filename.txt

        error=$(grep ERROR filename.txt | wc -l) # We look for the lines containing the word "ERROR" in the filename.txt file.
                                             # Then we redirect the output to the wc -l command that will count the number
                                             # of lines where the word ERROR appears.
    
        if [ $error -gt 0 ]; then # If this condition is satisfied, that means the word ERROR appeared at least once in
                                  # the log that's being examined in the current loop.
            echo "ERROR found in log $line" >> $mailcontents
        else
            echo "No errors found in $line" >> $mailcontents
        fi
    fi
echo "============" >> $mailcontents
done < filename.txt

if [ -s $mailcontents ]; then
    mail -s "Batch Job check on the server `hostname` - $(date +'%A %B %d, %Y')" nasirhussain4u4@gmail.com < $mailcontents
fi

# rm $mailcontents filename.txt # Delete auxiliary files when we're done.

        tail -100 $line > filename.txt

done < filename.txt

        tail -100 $line > tmp.txt
        error=$(grep ERROR tmp.txt | wc -l)

        error=$(tail -100 "$line" | grep -c "ERROR")

        tail -100 $line > filename.txt

        error=$(grep ERROR filename.txt | wc -l) # We look for the lines containing the word "ERROR" in the filename.txt file.
                                             # Then we redirect the output to the wc -l command that will count the number
                                             # of lines where the word ERROR appears.
    
        if [ $error -gt 0 ]; then # If this condition is satisfied, that means the word ERROR appeared at least once in
                                  # the log that's being examined in the current loop.
          echo "ERROR found in log $line" >> $mailcontents

   if tail -100 $line | grep -q ERROR
   then
        echo "ERROR found in log $line" >> $mailcontents