I'd like to prepend the vhost name in my ErrorLog and then pipe it into a program I wrote.
Is it possible to write Custom Error log format as it is with Access log?
Getting a custom error log format is more difficult. You can customize the access log easily with
In Apache 2.2 you cannot change the format of error_log easily - see http://httpd.apache.org/docs/2.2/logs.html#errorlog.
Apache 2.4 adds this support. See http://httpd.apache.org/docs/2.4/logs.html#errorlog.
With Apache 2.4 you can use the
Example (default format for threaded MPMs)
Example (similar to the 2.2.x format)
Advanced example with request/connection log IDs
Source: ErrorLogFormat Directive