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### 9.4 Formatting Variables

Throughout this manual you've probably noticed lots of variables called things like `gnus-group-line-format` and `gnus-summary-mode-line-format`. These control how Gnus is to output lines in the various buffers. There's quite a lot of them. Fortunately, they all use the same syntax, so there's not that much to be annoyed by.

Here's an example format spec (from the group buffer): ‘`%M%S%5y: %(%g%)\n`’. We see that it is indeed extremely ugly, and that there are lots of percentages everywhere.

Currently Gnus uses the following formatting variables: `gnus-group-line-format`, `gnus-summary-line-format`, `gnus-server-line-format`, `gnus-topic-line-format`, `gnus-group-mode-line-format`, `gnus-summary-mode-line-format`, `gnus-article-mode-line-format`, `gnus-server-mode-line-format`, and `gnus-summary-pick-line-format`.

All these format variables can also be arbitrary elisp forms. In that case, they will be `eval`ed to insert the required lines.

Gnus includes a command to help you while creating your own format specs. `M-x gnus-update-format` will `eval` the current form, update the spec in question and pop you to a buffer where you can examine the resulting Lisp code to be run to generate the line.