awk print error from Apache error logs

Apache log can contain several line of error. Counting the occurrence of each error is a good way to start.

Apache log separate field with "[ ]". Using sort for sorting error and uniq with -c option to count the number of occurrence.

Here to list all in error regardless of warning or error :

awk -F'[\[\]]+' '{print $7}' error.log | sort | uniq -c | sort -nr

To filter for error add the logic to awk :

awk -F'[\[\]]+' '$4 == "error"{print $7}' error.log | sort | uniq -c | sort -nr

From http://sudarmuthu.com/blog/how-to-print-unique-errorswith-count-from-apache-error-logs/