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The Log File Navigator, lnav, is an advanced log file viewer for the terminal. It provides an :ref:`easy-to-use interface<ui>` for monitoring and analyzing your log files with little to no setup. Simply point lnav at your log files and it will automatically detect the :ref:`log_formats`, index their contents, and display a combined view of all log messages. You can navigate through your logs using a variety of :ref:`hotkeys<hotkeys>`. :ref:`Commands<commands>` give you additional control over lnav's behavior for doing things like applying filters, tagging messages, and more. You can then analyze your log messages using the :ref:`sql-ext`.


When compiling from source, the following dependencies are required:


Check the downloads page to see if there are packages for your operating system. To compile from source, use the following commands:

.. prompt:: bash

   sudo make install

Viewing Logs

The arguments to lnav are the log files, directories, or URLs to be viewed. For example, to view all of the CUPS logs on your system:

.. prompt:: bash

   lnav /var/log/cups

The formats of the logs are determined automatically and indexed on-the-fly. See :ref:`log_formats` for a listing of the predefined formats and how to define your own.

If no arguments are given, lnav will try to open the syslog file on your system:

.. prompt:: bash



After starting lnav, you might want to set the :ref:`configuration options<Configuration>` mentioned below. Configuration in lnav is done using the :config command. To change a configuration option, start by pressing : to enter the command prompt. Then, type "config" followed by the option name and value.


Tab-completion is available for these configuration options and, in some cases, their values as well.


The keymap defines the mapping from :ref:`hotkeys<hotkeys>` to commands to execute. The default mapping is for "U.S." keyboards. The following command can be used to change the keymap:

:config /ui/keymap <keymap-name>

The builtin keymaps are:

uk:United Kingdom
us:United States

To create or customize a keymap, consult the :ref:`keymaps` section.


The visual styling of lnav can be customized using a theme. The following command can be used to the change the theme:

:config /ui/theme <theme-name>

The builtin themes are: default, eldar, grayscale, monocai, night-owl, solarized-dark, and solarized-light.

To create or customize a theme, consult the :ref:`themes` section.

Log Formats

In order for lnav to understand your log files, it needs to told how to parse the log messages using a log format definition. There are many log formats builtin and lnav will automatically determine the best format to use. In case your log file is not recognized, consult the :ref:`log_formats` section for information on how to create a format.