Is it possible without regex to separate log string into variables for desired pattern?

The string class has methods such as indexOf() which you can use to manually "search" a string for specific "separators". To then use methods like substring() to fetch, well substrings.

In other words: it is absolutely possible to write your own very specific parsing code that extracts values from a string.

But that means trying to re-invent an existing wheel; knowing that your attempts will cost a lot of time, and the outcome will be most likely incomplete and break on the very first log line you didn't anticipate.

And when I get your question right, you want to be able to provide a "format" such as: LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" that is then somehow used to dissect the log lines. Sorry - that is exactly what you use regular expressions for. So again: your approach boils down to inventing and implementing your own regex language and engine. Of course this is possible, but a waste of time.

Beyond that, consider this task to be very advanced. This is nothing a newbie can think of doing in reasonable amounts of time. Instead: spend your energy to learn to apply existing, well-proven, well-tested technology. In such situations, that is the way to go (also from a business perspective - anything else is also a waste of money).

And assuming this is for "learning purposes" - then the first paragraph tells you where to start. But beyond that:

• you have to first define your own "pattern language"
• then you have to implement a parser for such formats
• then you have to implement an engine that takes parsed formats as input and matches them onto input strings

As said: possible, but a ton of hard work.