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203 lines
7.4 KiB
Markdown
<!-- This is a comment for testing purposes -->
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[](https://github.com/tstack/lnav/actions?query=workflow%3Aci-build)
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[](https://docs.lnav.org)
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[](https://coveralls.io/github/tstack/lnav?branch=master)
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[](https://snapcraft.io/lnav)
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[<img src="https://assets-global.website-files.com/6257adef93867e50d84d30e2/62594fddd654fc29fcc07359_cb48d2a8d4991281d7a6a95d2f58195e.svg" height="20" alt="Discord Logo"/>](https://discord.gg/erBPnKwz7R)
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_This is the source repository for **lnav**, visit [https://lnav.org](https://lnav.org) for a high level overview._
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# LNAV -- The Logfile Navigator
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The Logfile Navigator is a log file viewer for the terminal. Given a
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set of files/directories, **lnav** will:
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- decompress as needed;
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- detect their format;
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- merge the files together by time into a single view;
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- tail the files, follow renames, find new files in directories;
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- build an index of errors and warnings;
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- [pretty-print JSON-lines](https://docs.lnav.org/en/latest/formats.html#json-lines).
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Then, in the **lnav** TUI, you can:
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- jump quickly to the previous/next error ([press `e`/`E`](https://docs.lnav.org/en/latest/hotkeys.html#spatial-navigation));
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- search using regular expressions ([press `/`](https://docs.lnav.org/en/latest/hotkeys.html#spatial-navigation));
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- highlight text with a regular expression ([`:highlight`](https://docs.lnav.org/en/latest/commands.html#highlight-pattern) command);
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- filter messages using [regular expressions](https://docs.lnav.org/en/latest/usage.html#regular-expression-match) or [SQLite expressions](https://docs.lnav.org/en/latest/usage.html#sqlite-expression);
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- pretty-print structured text ([press `P`](https://docs.lnav.org/en/latest/ui.html#pretty));
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- view a histogram of messages over time ([press `i`](https://docs.lnav.org/en/latest/ui.html#hist));
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- query messages using SQLite ([press `;`](https://docs.lnav.org/en/latest/sqlext.html))
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## Screenshot
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The following screenshot shows a mix of syslog and web access log
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files. Failed requests are shown in red. Identifiers, like IP
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address and PIDs are semantically highlighted.
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[](docs/assets/images/lnav-front-page.png)
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## Why not **just** use `tail`/`grep`/`less`?
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The standard Unix utilities are great for processing raw text lines,
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however, they do not understand log messages. Tail can watch
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multiple files at a time, but it won't display messages in order by
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time and you can't scroll backwards. Grep will only find matching
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lines, but won't return a full multi-line log message. Less can only
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display a single file at a time. Also, none of these basic tools
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handle compressed files.
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## Try online before installing
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You can SSH into a demo node to play with lnav before installing.
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The "playground" account starts lnav with a couple of log files as
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an example:
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[`$ ssh playground@demo.lnav.org`](ssh://playground@demo.lnav.org)
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The "tutorial 1" account is an interactive tutorial that can teach
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you the basics of operation:
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[`$ ssh tutorial1@demo.lnav.org`](ssh://tutorial1@demo.lnav.org)
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## Installation
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[Download a statically-linked binary for Linux/MacOS from the release page](https://github.com/tstack/lnav/releases/latest#release-artifacts)
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### Brew on MacOS
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```console
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$ brew install lnav
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```
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## Usage
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Simply point **lnav** at the files or directories you want to
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monitor, it will figure out the rest:
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```console
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$ lnav /path/to/file1 /path/to/dir ...
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```
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The **lnav** TUI will pop up right away and begin indexing the
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files. Progress is displayed in the "Files" panel at the
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bottom. Once the indexing has finished, the LOG view will display
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the log messages that were recognized[^1]. You can then use the
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usual hotkeys to move around the view (arrow keys or
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`j`/`k`/`h`/`l` to move down/up/left/right).
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See the [Usage section](https://docs.lnav.org/en/latest/usage.html)
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of the online documentation for more information.
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[^1]: Files that do not contain log messages can be seen in the
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TEXT view (reachable by pressing `t`).
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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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```
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$ journalctl | lnav
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```
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or in follow mode:
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```
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$ journalctl -f | lnav
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```
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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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```
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$ journalctl -o short-iso | lnav
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```
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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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```
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$ journalctl -o json | lnav
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```
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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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```
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$ journalctl -a -o json | lnav
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```
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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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```
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$ journalctl -o json --output-fields=MESSAGE,PRIORITY,_PID,SYSLOG_IDENTIFIER,_SYSTEMD_UNIT | lnav
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```
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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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## Support
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Please file issues on this repository or use the discussions section.
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The following alternatives are also available:
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- [support@lnav.org](mailto:support@lnav.org)
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- [Discord](https://discord.gg/erBPnKwz7R)
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- [Google Groups](https://groups.google.com/g/lnav)
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## Links
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- [Main Site](https://lnav.org)
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- [**Documentation**](https://docs.lnav.org) on Read the Docs
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- [Internal Architecture](ARCHITECTURE.md)
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## Contributing
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- [Become a Sponsor on GitHub](https://github.com/sponsors/tstack)
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### Building From Source
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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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- libpcre2 - The Perl Compatible Regular Expression v2 (PCRE2) 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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- wireshark - The 'tshark' program is used to interpret pcap files.
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- cargo/rust - The Rust language is used to build the PRQL compiler.
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#### Build
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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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```console
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$ ./configure
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$ make
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$ sudo make install
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```
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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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