lnav/README.md
2020-12-27 21:20:58 -08:00

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[![Build Status](https://travis-ci.org/tstack/lnav.png)](https://travis-ci.org/tstack/lnav)
[![Build status](https://ci.appveyor.com/api/projects/status/24wskehb7j7a65ro?svg=true)](https://ci.appveyor.com/project/tstack/lnav)
[![lnav](https://snapcraft.io//lnav/badge.svg)](https://snapcraft.io/lnav)
[![LoC](https://tokei.rs/b1/github/tstack/lnav)](https://github.com/tstack/lnav).
_This is the source repository for **lnav**, visit [http://lnav.org](http://lnav.org) for a high level overview._
# LNAV -- The Logfile Navigator
The Log File Navigator, **lnav** for short, is an advanced log file viewer
for the small-scale. It is a terminal application that can understand
your log files and make it easy for you to find problems with little to
no setup.
### Links
* [Main Site](https://lnav.org)
* [**Documentation**](https://lnav.readthedocs.io) on Read the Docs
## Contributing
* [Become a Sponsor on GitHub](https://github.com/sponsors/tstack)
* [Make a one-time donation on Ko-fi](https://ko-fi.com/tstack)
## Features
* Log messages from different files are collated together into a single view
* Automatic detection of log format
* Automatic decompression of GZip and BZip2 files
* Filter log messages based on regular expressions
* Use SQL to analyze your logs
* And more...
## Prerequisites
The following software packages are required to build lnav:
* gcc/clang - A C++14-compatible compiler.
* libpcre - The Perl Compatible Regular Expression (PCRE) library.
* sqlite - The SQLite database engine. Version 3.9.0 or higher is required.
* ncurses - The ncurses text UI library.
* readline - The readline line editing library.
* zlib - The zlib compression library.
* bz2 - The bzip2 compression library.
* libcurl - The cURL library for downloading files from URLs. Version 7.23.0 or higher is required.
## Installation
Lnav follows the usual GNU style for configuring and installing software:
Run `./autogen.sh` if compiling from a cloned repository.
$ ./configure
$ make
$ sudo make install
## Cygwin users
It should compile fine in Cygwin.
Alternatively, you can get the generated binary from [AppVeyor](https://ci.appveyor.com/project/tstack/lnav) artifacts.
Remember that you still need the lnav dependencies under Cygwin, here is a quick way to do it:
setup-x86_64.exe -q -P libpcre1 -P libpcrecpp0 -P libsqlite3_0 -P libstdc++6
Currently, the x64 version seems to be working better than the x86 one.
## Usage
The only file installed is the executable, `lnav`. You can execute it
with no arguments to view the default set of files:
$ lnav
You can view all the syslog messages by running:
$ lnav /var/log/messages*
### Usage with `systemd-journald`
On systems running `systemd-journald`, you can use `lnav` as the pager:
$ journalctl | lnav
or in follow mode:
$ journalctl -f | lnav
Since `journalctl`'s default output format omits the year, if you are
viewing logs which span multiple years you will need to change the
output format to include the year, otherwise `lnav` gets confused:
$ journalctl -o short-iso | lnav
It is also possible to use `journalctl`'s json output format and `lnav`
will make use of additional fields such as PRIORITY and _SYSTEMD_UNIT:
$ journalctl -o json | lnav
In case some MESSAGE fields contain special characters such as
ANSI color codes which are considered as unprintable by journalctl,
specifying `journalctl`'s `-a` option might be preferable in order
to output those messages still in a non binary representation:
$ journalctl -a -o json | lnav
If using systemd v236 or newer, the output fields can be limited to
the ones actually recognized by `lnav` for increased efficiency:
$ journalctl -o json --output-fields=MESSAGE,PRIORITY,_PID,SYSLOG_IDENTIFIER,_SYSTEMD_UNIT | lnav
If your system has been running for a long time, for increased
efficiency you may want to limit the number of log lines fed into
`lnav`, e.g. via `journalctl`'s `-n` or `--since=...` options.
In case of a persistent journal, you may want to limit the number
of log lines fed into `lnav` via `journalctl`'s `-b` option.
## Screenshot
The following screenshot shows a syslog file. Log lines are displayed with
highlights. Errors are red and warnings are yellow.
[![Screenshot](http://tstack.github.io/lnav/lnav-syslog-thumb.png)](http://tstack.github.io/lnav/lnav-syslog.png)
## See Also
[Angle-grinder](https://github.com/rcoh/angle-grinder) is a tool to slice and dice log files on the command-line.
If you're familiar with the SumoLogic query language, you might find this tool more comfortable to work with.