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[](https://travis-ci.org/tstack/lnav)
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[](https://ci.appveyor.com/project/tstack/lnav)
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[](https://snapcraft.io/lnav)
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[](https://github.com/tstack/lnav).
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_This is the source repository for **lnav**, visit [http://lnav.org](http://lnav.org) for a high level overview._
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# LNAV -- The Logfile Navigator
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The Log File Navigator, **lnav** for short, is an advanced log file viewer
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for the small-scale. It is a terminal application that can understand
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your log files and make it easy for you to find problems with little to
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no setup.
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### Links
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* [Main Site](https://lnav.org)
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* [**Documentation**](https://lnav.readthedocs.io) on Read the Docs
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## Contributing
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* [Become a Sponsor on GitHub](https://github.com/sponsors/tstack)
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* [Make a one-time donation on Ko-fi](https://ko-fi.com/tstack)
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## Features
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* Log messages from different files are collated together into a single view
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* Automatic detection of log format
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* Automatic decompression of GZip and BZip2 files
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* Filter log messages based on regular expressions
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* Use SQL to analyze your logs
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* And more...
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## Prerequisites
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The following software packages are required to build lnav:
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* gcc/clang - A C++14-compatible compiler.
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* libpcre - The Perl Compatible Regular Expression (PCRE) library.
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* sqlite - The SQLite database engine. Version 3.9.0 or higher is required.
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* ncurses - The ncurses text UI library.
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* readline - The readline line editing library.
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* zlib - The zlib compression library.
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* bz2 - The bzip2 compression library.
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* libcurl - The cURL library for downloading files from URLs. Version 7.23.0 or higher is required.
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* libarchive - The libarchive library for opening archive files, like zip/tgz.
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## Installation
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Lnav follows the usual GNU style for configuring and installing software:
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Run `./autogen.sh` if compiling from a cloned repository.
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$ ./configure
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$ make
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$ sudo make install
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## Cygwin users
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It should compile fine in Cygwin.
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Alternatively, you can get the generated binary from [AppVeyor](https://ci.appveyor.com/project/tstack/lnav) artifacts.
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Remember that you still need the lnav dependencies under Cygwin, here is a quick way to do it:
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setup-x86_64.exe -q -P libpcre1 -P libsqlite3_0 -P libstdc++6
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Currently, the x64 version seems to be working better than the x86 one.
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## Usage
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The only file installed is the executable, `lnav`. You can execute it
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with no arguments to view the default set of files:
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$ lnav
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You can view all the syslog messages by running:
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$ lnav /var/log/messages*
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### Usage with `systemd-journald`
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On systems running `systemd-journald`, you can use `lnav` as the pager:
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$ journalctl | lnav
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or in follow mode:
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$ journalctl -f | lnav
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Since `journalctl`'s default output format omits the year, if you are
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viewing logs which span multiple years you will need to change the
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output format to include the year, otherwise `lnav` gets confused:
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$ journalctl -o short-iso | lnav
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It is also possible to use `journalctl`'s json output format and `lnav`
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will make use of additional fields such as PRIORITY and _SYSTEMD_UNIT:
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$ journalctl -o json | lnav
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In case some MESSAGE fields contain special characters such as
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ANSI color codes which are considered as unprintable by journalctl,
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specifying `journalctl`'s `-a` option might be preferable in order
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to output those messages still in a non binary representation:
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$ journalctl -a -o json | lnav
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If using systemd v236 or newer, the output fields can be limited to
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the ones actually recognized by `lnav` for increased efficiency:
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$ journalctl -o json --output-fields=MESSAGE,PRIORITY,_PID,SYSLOG_IDENTIFIER,_SYSTEMD_UNIT | lnav
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If your system has been running for a long time, for increased
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efficiency you may want to limit the number of log lines fed into
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`lnav`, e.g. via `journalctl`'s `-n` or `--since=...` options.
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In case of a persistent journal, you may want to limit the number
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of log lines fed into `lnav` via `journalctl`'s `-b` option.
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## Screenshot
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The following screenshot shows a syslog file. Log lines are displayed with
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highlights. Errors are red and warnings are yellow.
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[](http://tstack.github.io/lnav/lnav-syslog.png)
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## See Also
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[Angle-grinder](https://github.com/rcoh/angle-grinder) is a tool to slice and dice log files on the command-line.
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If you're familiar with the SumoLogic query language, you might find this tool more comfortable to work with.
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