Find Top 404 Error Pages with Apache

A quick one-liner to find the most common pages giving 404 errors on your apache2 setup. Set this up as a shell alias to get easy access at any time.

cut -d'"' -f2,3 /var/log/apache/access.log | awk '$4=404{print $4" "$2}' | sort | uniq -c | sort -rg

Replace /var/log/apache/access.log with the path to your own Apache setup. On web hosts this may be under ~/logs/apache or elsewhere.

This one liner breaks down as follows:

1. cut splits the input (the logfile) by -d delimiter and returning only the fields given by `-f``
2. Output is piped into awk which searches for lines where field 4 = 404, returning these as a line containing 404 URL
3. These are then sorted (so duplicates can be counted) with sort
4. uniq -c counts the duplicates chucks them away and appends a number to the beginning of each row that is left
5. The resulting output is then sorted numerically -g and -r reverse (highest first - remove this to get the top ones at the bottom of the list)