The problem statement:
I have a standard thttpd web server log file. It contains different columns (like IP address, request result code, request type etc) including a date column with the format [31/Mar/2002:19:30:41 +0200].

I have developed a command line log analyzer that displays different statistics from the log (e.g. 1- IP with most connection attempts, 2- the most common result codes etc.). In fact to view every stat the user will have to give a specific switch to my utility (like -i and -c respectively with the above examples).

Now comes the problem; with every stat the user can ask to limit the results for either 1. previous n hours. or 2. previous n days. I am unable to use the date from the file with format [31/Mar/2002:19:30:41 +0200] and make a comparison with the timestamp of previous n hours or previous n days.

Constraint: I have to attempt this only in bash.

For the hour you can

cut -d':' -f2

and do simple math to get a start time. For the day you can

cut -d'/' -f1

That would be more tricky as you would have to logic out the rollback to a previous month.

That's the brute force way. Hopefully someone will know a more elegant solution to actually compare a date type structure.

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The above is our standard homework response......In this case, I think the key thing is to explain what the problem is--including what code you are using and what exactly happens. Also, when you say "only bash", does that mean you are allowed to use standard utilities like AWK and SED?