How to create a system to detect text structure of a file?
Based on your current examples. 


You have an ML that is doing work across multiple systems and users. Generating logs.
The logs can be grouped or classed (e.g. $F1, F2,...,FN$) by: 


i) the operating System used (e.g. Android, Windows etc) and
ii) the error or message generated. The error messages are differentiated by tab white space.  



If you cannot work out the log class using some logic, you could look to engineer features with regex to capture the source OS and the tabbed structural information in the error lines.

|---------------------|------------------|
| Error detail        |     n_tabs       |
|---------------------|------------------|
|  string_error       |         0        |
|---------------------|------------------|