When doing an error analysis with a log file it often happens that I don't know in advance what I am interested in, but want to go the other way: I look at the logfile, and want to remove uninteresting logfile lines with common messages consecutively until only the interesting stuff is left. E.g. I first want to remove all messages containing "INFO", then all log messages containing a specific very common warning. In the rest there is a common error message which is uncritical, so I want to remove this as well. And so forth, until I get to the meat. Is there anything that supports this process? Common logfile viewers seem to only support highlighting stuff, which isn't too helpful if I don't know the problem in advance.

Preferably the process should work as follows: The logfile is displayed, I can scroll around, and when ever I identify a common pattern I can select it via mouse and hide everything that contains that pattern with one click.

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    Given that log files are usually ASCII you could look at editors that (1) can handle large files and (2) have good macro capabilities. You then e.g. write a macro "Remove all lines containing [selected text]" and execute that while investigating. – user416 Aug 26 '15 at 9:16
  • It would also help if you could mention what OS this tool should run on: Linux? Mac OS(X)? Windows? There might be solutions not available for all platforms. – Izzy Aug 26 '15 at 9:29
  • @Izzy If there are solutions that run only on some platforms, I could adapt. So I'd rather make it general. – Hans-Peter Störr Aug 26 '15 at 9:38
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    OK, understood. You might wish to include that with your question (you can always edit it) – something like "preferably for X, but other platforms are accepted as well". At SR, we prefer to focus :) – Izzy Aug 26 '15 at 9:42
  • @hstoerr When you say remove, you mean you'd like to filter out lines containing a specific string? As per your example, you start with a full log file, then you filter out lines containing "INFO", then you filter out even more lines by adding another filtering string in a logical AND with the previous one, etc.? – mguassa Aug 26 '15 at 19:19

The LogExpert log file viewer for Windows allows you to highlight lines matching regular expressions, which I use to dim out uninteresting lines that match the expression.

It also has a Filter view which has an Invert Match feature, allowing you to show all lines except ones which match certain expressions.

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