katran009/dirwatcher-assignment

Objective:

Create a long running program Demonstrate signal handling Demonstrate program logging Use exception handling to keep the program running Create and structure your own code repository using best practices Show that you know how to read a set of requirements and deliver on them, asking for clarification if anything is unclear.

Goal

For this assessment you will create your own small long-running program named dirwatcher.py. This will give you experience in structuring a long-running program, which will help you with the SlackTweet project later on. The dirwatcher.py program should accept some command line arguments that will instruct it to monitor a given directory for text files that are created within the monitored directory. Your dirwatcher.py program will continually search within all files in the directory for a 'magic' string which is provided as a command line argument. This can be implemented with a timed polling loop. If the magic string is found in a file, your program should log a message indicating which file and line number the magic text was found. Once a magic text occurrence has been logged, it should not be logged again unless it appears in the file as another subsequent line entry later on.

Files in the monitored directory may be added or deleted or appended at any time by other processes. Your program should log a message when new files appear or other previously watched files disappear. Assume that files will only be changed by appending to them. That is, anything that has previously been written to the file will not change. Only new content will be added to the end of the file. You don't have to continually re-check sections of a file that you have already checked.

Your program should terminate itself by catching SIGTERM or SIGINT (be sure to log a termination message). The OS will send a signal event to processes that it wants to terminate from the outside. Think about when a sys admin wants to shutdown the entire computer for maintenance with a sudo shutdown command. If your process has open file handles, or is writing to disk, or is managing other resources, this is the OS way of telling your program that you need to cleanup, finish any writes in progress, and release resources before shutting down.

NOTE that handling OS signals and polling the directory that is being watched are two separate functions of your program. You won't be getting an OS signal when files are created or deleted.