UNIX for Advanced & Expert Users

#!/bin/bash
mailcontents=mailbody
while read line
  do
      if [ ! -f $line ]; then
          echo "The file $line doesn't exist. Continuing with the next file..." >> $mailcontents
          echo "============" >> $mailcontents
          continue
      else
          last_mod_time=$(stat -c '%Y' $line) # this line checks the log's last modification time and converts it to Unix's epoch
          last_24_hours=$(date +%s -d "24 hours ago") # 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 > checklog

          error=$(grep ERROR checklog | wc -l) # We look for the lines containing the word "ERROR" in the checklog 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 < mylogs
  
  if [ -s $mailcontents ]; then
      mail -s "Log errors and last modification times - $(date +'%A %B %d, %Y')" myemail@gmail.com < $mailcontents
  fi
  
  rm $mailcontents checklog # Delete auxiliary files when we're done.

last_mod_time=$(stat -c '%Y' $line) # this line checks the log's last modification time and converts it to Unix's epoch
last_24_hours=$(date +%s -d "24 hours ago") # this line returns the epoch for the current timestamp minus 24 hours