Write shell script to scan text files for keyword

A "watchdog" script running in backgroud on linux servers and scanning log files in two differents folders. The log filenames to scan can start with 4 differents patterns followed by date (yyyymmdd) and time (hhmmss). Ex . If pattern1= "app1" then many log files would be created several times per day and would look like [login to view URL] [login to view URL], etc The watchdog need to scan the logfiles at a user define time interval and check for specific error keywords. The different error keywords to scan can be stored in a separate config file and each keyword is also assigned one of three severity level (low, warning, alert). When an error is trapped in one of the log files, then the log filename, the line number and the line has to be stored somewhere and if it's severity level "alert" than an email is sent containing these info.