Here is an example of using `if` to check if a file exists and if it is a regular file. If it exists, check whether or not it has a size greater than 0.
 
 #!/bin/bash

 echo "Which error log are you checking today? "
 read answer

 if [ -f /opt/logs/$answer*.errors ]
 then
 if [ -s /opt/logs/$answer*.errors ]
 then
 echo "Content is present in the $answer error log file."
 else
 echo "No errors are present in the $answer error log file."
 fi
 else
 echo "$answer does not have an error log at this time."
 fi