This is my log filter. There are many like it, but this one is mine.

Alf is intended to be a convenient way of performing common extraction and processing tasks on webserver log files:

• Selecting lines based on field contents such as url or status code.
• Extracting only certain fields from logfiles.
• Counting the number of lines that match a pattern.

It currently parses some of the more commonly used apache formats, but it could parse many others, with a little work.

I am currently not very happy with the command line options, so it is likely that I will change both their names and the defaults in future commits.

You will need Python >= 2.4 installed.

• Download the file 'alf' either
• from https://github.com/bleach/alf/raw/master/alf
• or via git by doing "git clone git@github.com:bleach/alf.git"
• Copy the file alf into your $PATH

If you have the psyco pythom module installed, alf will use it in an attempt to improve performance.

1. Extract all the logged requests which had the status code 404:

   alf --status-regex='404' logfile

2. Extract all the requests to /robots.txt:

   alf --url-regex='^/robots.txt' logfile

Tech debt:

• Make a log format a more structured thing including:
  • regex for parsing the log
  • knowledge of how to translate timestamp fields into a python datetime
• Address the confusion when you --print-invalid and --print-lines at the same time

Features:

• Detect log formats automatically.
• Query on fields which are in non-default log formats.
• Add an option to sort output by date.
• Configuration file to add more log formats.
• Make it easier to call alf from other scripts.

Internals:

• Testing:
• Unit tests.
• Test runner to run tests on all supported python versions.
• Simple integration tests against sample logfiles.
• Performance benchmarks.