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https://github.com/pamburus/hl

A fast and powerful log viewer and processor that translates JSON or logfmt logs into a pretty human-readable format.
https://github.com/pamburus/hl

cli command-line-tool hl human json json-log json-logging json-logs log log-viewer logging logs rust structured-logging translates-json-logs viewer

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A fast and powerful log viewer and processor that translates JSON or logfmt logs into a pretty human-readable format.

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README 

        
# hl [![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov]



A fast and powerful log viewer and processor that translates JSON or logfmt logs into a pretty human-readable format.

High performance and convenient features are the main goals.



## Features overview



* [Automatic usage](#automatic-usage-of-pager) of the [less](https://github.com/vbwagner/less) pager by default for convenience.

* Log streaming with the `-P` flag that disables the pager.

* Log record [filtering by field key/value pairs](#filtering-by-field-values) with the `-f` option with support for hierarchical keys.

* Quick and easy [filtering by level](#quick-filtering-by-log-level) with the `-l` option.

* Quick and easy [filtering by timestamp range](#filtering-by-time-range) using the `--since` and `--until` options and intuitive formats:

    * RFC-3339 timestamp format.

    * Current configured timestamp output format with the `-t` option or environment variable.

    * Human friendly shortcuts like `today`, `yesterday`, `friday` or relative offsets like `-3h` or `-14d`.

* Quick and easy [hiding and revealing](#hiding-or-revealing-selected-fields) of fields with the `-h` option.

* Hide empty fields with the `-e` flag.

* Lightning fast [message sorting](#sorting-messages-chronologically) with automatic indexing for local files using the `-s` flag.

    * Handles ~1 GiB/s for the first scan and allows fast filtering by timestamp range and level without scanning the data afterwards.

    * Works fast with hundreds of local files containing hundreds of gigabytes of data.

    * Reindexes large, growing files at lightning speed, skipping unmodified blocks, ~10 GiB/s.

* [Follow mode](#sorting-messages-chronologically-with-following-the-changes) with live message sorting by timestamp from different sources using the `-F` flag and preview of several recent messages with the `--tail` option.

* Custom complex [queries](#performing-complex-queries) that can include and/or conditions and much more.

* Non-JSON prefixes with `--allow-prefix` flag.

* Displays timestamps in UTC by default and supports easy timezone switching with the `-Z` option and the `-L` flag for a local timezone.

* Customizable via [configuration](#configuration-files) file and environment variables, supports easy [theme switching](#selecting-current-theme) and custom [themes](#custom-themes).



## Performance comparison chart



### Performance comparison with [humanlog](https://github.com/humanlogio/humanlog), [hlogf](https://github.com/ssgreg/hlogf) and [fblog](https://github.com/brocode/fblog) on a 2.3 GiB log file



![performance chart](doc/performance-chart.svg)



* See [performance](#performance) section for more details.



## Installation options



* Install using [homebrew](https://brew.sh) on macOS or Linux



    ```

    brew install pamburus/tap/hl

    ```



* Download and extract using `curl` and `tar` on macOS



    ```

    curl -sSfL https://github.com/pamburus/hl/releases/latest/download/hl-macos.tar.gz | tar xz

    ```



* Download and extract using `curl` and `tar` on Linux



    ```

    curl -sSfL https://github.com/pamburus/hl/releases/latest/download/hl-linux-x86_64-musl.tar.gz | tar xz

    ```



* Install [AUR package](https://aur.archlinux.org/packages/hl-log-viewer-bin) on Arch Linux



    ```

    yay -S hl-log-viewer-bin

    ```



* Install using [cargo](https://www.rust-lang.org/tools/install)



    ```

    cargo install --locked --git https://github.com/pamburus/hl.git

    ```



* Download latest release from [download page](https://github.com/pamburus/hl/releases/latest)



## Examples



### Screenshot



![screenshot-light](https://github.com/pamburus/hl-extra/raw/90be58af2fb91d5b5e7ce3b74c3b567611379c40/screenshot/universal/light.png#gh-light-mode-only)

![screenshot-dark](https://github.com/pamburus/hl-extra/raw/90be58af2fb91d5b5e7ce3b74c3b567611379c40/screenshot/universal/dark.png#gh-dark-mode-only)



See other [screenshots](https://github.com/pamburus/hl-extra/tree/90be58af2fb91d5b5e7ce3b74c3b567611379c40/screenshot#readme)



## Features and usage



### Concatenation of multiple log files



- Concatenate all log files



    Command



    ```

    $ hl $(ls -tr /var/log/example/*.log)

    ```

    Concatenates and humanizes all `*.log` files found in `/var/log/example/`.



### Support for gzipped log files



- Concatenate all log files including gzipped log files



    Command



    ```

    $ hl $(ls -tr /var/log/example/*.{log,log.gz})

    ```

    Concatenates and humanizes all `*.log` and `*.log.gz` files found in `/var/log/example/`.



### Automatic usage of pager



- Use default pager with default parameters



    Command



    ```

    $ hl example.log

    ```

    Automatically opens `less` pager with default parameters.



- Override options for default pager

    

    Command



    ```

    $ LESS=-SR hl example.log

    ```

    Opens `less` pager with disabled line wrapping.



- Use custom pager

    

    Command



    ```

    $ PAGER=bat hl example.log

    ```

    Opens `bat` pager.



### Quick filtering by log level



- Errors only



    Command 



    ```

    $ hl -l e

    ```



    Displays only error log level messages.



- Errors and warnings



    Command 



    ```

    $ hl -l w

    ```

    Displays only warning and error log level messages.



- Errors, warnings and informational



    Command 



    ```

    $ hl -l i

    ```

    Displays all log messages except debug level messages.



### Using live log streaming



- Command



    ```

    $ tail -f example.log | hl -P

    ```

    Tracks changes in the example.log file and displays them immediately.

    Flag `-P` disables automatic using of pager in this case.



### Filtering by field values



- Command



    ```

    $ hl example.log --filter component=tsdb

    ```

    Displays only messages where the `component` field has the value `tsdb`.



- Command



    ```

    $ hl example.log -f component!=tsdb -f component!=uninteresting

    ```

    Displays only messages where the `component` field has a value other than `tsdb` or `uninteresting`.



- Command



    ```

    $ hl example.log -f provider~=string

    ```

    Displays only messages where the `provider` field contains the `string` sub-string.



- Command



    ```

    $ hl example.log -f 'provider!~=string'

    ```

    Displays only messages where the `provider` field does not contain the `string` sub-string.



### Performing complex queries



- Command



    ```

    $ hl my-service.log --query 'level > info or status-code >= 400 or duration > 0.5'

    ```

    Displays messages that either have a level higher than info (i.e. warning or error) or have a status code field with a numeric value >= 400 or a duration field with a numeric value >= 0.5.



- Command



    ```

    $ hl my-service.log -q '(request in (95c72499d9ec, 9697f7aa134f, bc3451d0ad60)) or (method != GET)'

    ```

    Displays all messages that have the 'request' field with one of these values, or the 'method' field with a value other than 'GET'.



- Complete set of supported operators



    * Logical operators

        * Logical conjunction - `and`, `&&`

        * Logical disjunction - `or`, `||`

        * Logical negation - `not`, `!`

    * Comparison operators

        * Equal - `eq`, `=`

        * Not equal - `ne`, `!=`

        * Greater than - `gt`, `>`

        * Greater or equal - `ge`, `>=`

        * Less than - `lt`, `<`

        * Less or equal - `le`, `<=`

    * String matching operators

        * Sub-string check - (`contain`, `~=`), (`not contain`, `!~=`)

        * Wildcard match - (`like`), (`not like`)

            * Wildcard characters are: `*` for zero or more characters and `?` for a single character

        * Regular expression match - (`match`, `~~=`), (`not match`, `!~~=`)

    * Operators with sets

        * Test if value is one of the values in a set - `in (v1, v2)`, `not in (v1, v2)`

        * Test if value is one of the values in a set loaded from a file - `in @filename`, `not in @filename`, assuming that each element is a line in the file, which can be either a simple string or a JSON string

        * Test if value is one of the values in a set loaded stdin - `in @-`, `not in @-`

    

- Notes



    * Special field names that are reserved for filtering by predefined fields regardless of the actual source field names used to load the corresponding value: `level`, `message`, `caller` and `logger`.

    * To address a source field with one of these names instead of predefined fields, add a period before its name, i.e., `.level` will perform a match against the "level" source field.

    * To address a source field by its exact name, use a JSON-formatted string, i.e. `-q '".level" = info'`.

    * To specify special characters in field values, also use a JSON-formatted string, i.e. 

        ```

        $ hl my-service.log -q 'message contain "Error:\nSomething unexpected happened"'

        ```



### Filtering by time range



- Command



    ```

    $ hl example.log --since 'Jun 19 11:22:33' --until yesterday

    ```

    Displays only messages that occurred after Jun 19 11:22:33 UTC of the current year (or the previous year if the current date is less than Jun 19 11:22:33) and before yesterday midnight.



- Command



    ```

    $ hl example.log --since -3d

    ```

    Displays only messages from the past 72 hours.



- Command



    ```

    $ hl example.log --until '2021-06-01 18:00:00' --local

    ```

    Displays only messages that occurred before 6 PM local time on June 1, 2021, and shows timestamps in local time.



### Hiding or revealing selected fields



- Command



    ```

    $ hl example.log --hide provider

    ```

    Hides field `provider`.



- Command



    ```

    $ hl example.log --hide '*' --hide '!provider'

    ```

    Hides all fields except `provider`.



- Command



    ```

    $ hl example.log -h headers -h body -h '!headers.content-type'

    ```

    Hides fields `headers` and `body` but shows a single sub-field `content-type` inside field `headers`.



### Sorting messages chronologically



- Command



    ```

    $ hl -s *.log

    ```

    Displays log messages from all log files in the current directory sorted in chronological order.



### Sorting messages chronologically with following the changes



- Command



    ```

    $ hl --sync-interval-ms 500 -F <(kubectl logs -l app=my-app-1 -f) <(kubectl logs -l app=my-app-2 -f)

    ```

    Runs without a pager in follow mode by merging messages from the outputs of these 2 commands and sorting them chronologically within a custom 500ms interval.



- Command



    ```

    $ hl -F --tail 100 app1.log app2.log app3.log

    ```

    Runs without a pager in follow mode, following the changes in three log files in the current directory and sorting them chronologically at a default interval of 100ms.

    Preloads 100 lines from the end of each file before filtering.



### Configuration files



- Configuration file is automatically loaded if found in a predefined platform-specific location.



    | OS      | Location                                                  |

    | ------- | --------------------------------------------------------- | 

    | macOS   | ~/.config/hl/config.{yaml,toml,json}                      |

    | Linux   | ~/.config/hl/config.{yaml,toml,json}                      |

    | Windows | %USERPROFILE%\AppData\Roaming\hl\config.{yaml,toml,json}  |



- The path to the configuration file can be overridden using the HL_CONFIG environment variable.



- All parameters in the configuration file are optional and can be omitted. In this case, default values are used.



#### Default configuration file



- [config.yaml](etc/defaults/config.yaml)



### Environment variables



- Many parameters that are defined in command line arguments and configuration files can also be specified by environment variables.



#### Precedence of configuration sources (from lowest priority to highest priority)

* Configuration file

* Environment variables

* Command-line arguments



#### Examples

* `HL_TIME_FORMAT='%y-%m-%d %T.%3N'` overrides the time format specified in the configuration file.

* `HL_TIME_ZONE=Europe/Berlin` overrides the time zone specified in the configuration file.

* `HL_CONCURRENCY=4` overrides the concurrency limit specified in the configuration file.

* `HL_PAGING=never` specifies the default value for the paging option, but it can be overridden by command line arguments.



### Themes



#### Stock themes

- [themes](etc/defaults/themes/)



#### Selecting current theme

* Using `theme` value in the configuration file.

* Using environment variable, i.e. `HL_THEME=classic`, overrides the value specified in configuration file.

* Using command-line argument, i.e. `--theme classic`, overrides all other values.



#### Selecting themes with preview

To select themes with preview [fzf](https://github.com/junegunn/fzf) tool can be used like this:

```bash

hl --list-themes | fzf --preview-window="top,80%" --preview="head -n 100 example.log | hl -c --theme {}"

```



#### Custom themes

- Custom themes are automatically loaded when found in a predefined platform-specific location.



    | OS      | Location                                                   |

    | ------- | ---------------------------------------------------------- | 

    | macOS   | ~/.config/hl/themes/*.{yaml,toml,json}                     |

    | Linux   | ~/.config/hl/themes/*.{yaml,toml,json}                     |

    | Windows | %USERPROFILE%\AppData\Roaming\hl\themes\*.{yaml,toml,json} |



- Format description

  - Section `elements` contains styles for predefined elements.

  - Section `levels` contains optional overrides for styles defined in `elements` sections per logging level, which are [`debug`, `info`, `warning`, `error`].

  - Each element style contains optional `background`, `foreground` and `modes` parameters.

  - Example

    ```yaml

    elements:

        :

            foreground: 

            background: 

            modes: [, , ...]

    levels:

        :

            :

                foreground: 

                background: 

                modes: [, , ...]

    ```

  - Color format is one of

    - Keyword `default` specifies default color defined by the terminal.

    - ASCII basic color name, one of

      - `black`

      - `red`

      - `green`

      - `yellow`

      - `blue`

      - `magenta`

      - `cyan`

      - `white`

      - `bright-black`

      - `bright-red`

      - `bright-green`

      - `bright-yellow`

      - `bright-blue`

      - `bright-magenta`

      - `bright-cyan`

      - `bright-white`

    - 256-color palette code, from `0` to `255`.

    - RGB color in hex web color format, i.e. `#FFFF00` for bright yellow color.

  - Modes is a list of additional styles, each of them is one of

    - `bold`

    - `faint`

    - `italic`

    - `underline`

    - `slow-blink`

    - `rapid-blink`

    - `reverse`

    - `conceal`

    - `crossed-out`



### Used terminal color schemes



#### iTerm2

* [One Dark Neo](https://gist.github.com/pamburus/0ad130f2af9ab03a97f2a9f7b4f18c68/746ca7103726d43b767f2111799d3cb5ec08adbb)

* Built-in "Light Background" color scheme



#### Alacritty

* [One Dark Neo](https://gist.github.com/pamburus/e27ebf60aa17d126f5c879f06112edd6/a1e66d34a65b883f1cb8ec28820cc0c53233e3aa#file-alacritty-yml-L904)

  * Note: It is recommended to use `draw_bold_text_with_bright_colors: true` setting

* [Light](https://gist.github.com/pamburus/e27ebf60aa17d126f5c879f06112edd6/a1e66d34a65b883f1cb8ec28820cc0c53233e3aa#file-alacritty-yml-L875)

  * Note: It is recommended to use `draw_bold_text_with_bright_colors: false` setting



### Complete set of options and flags



```

JSON and logfmt log converter to human readable representation



Usage: hl [OPTIONS] [FILE]...



Arguments:

  [FILE]...  Files to process



Options:

      --config                     Configuration file path [env: HL_CONFIG=]

  -s, --sort                             Sort messages chronologically

  -F, --follow                           Follow input streams and sort messages chronologically during time frame set by --sync-interval-ms option

      --tail                          Number of last messages to preload from each file in --follow mode [default: 10]

      --sync-interval-ms   Synchronization interval for live streaming mode enabled by --follow option [default: 100]

      --paging                     Control pager usage (HL_PAGER or PAGER) [env: HL_PAGING=] [default: auto] [possible values: auto, always, never]

  -P                                     Handful alias for --paging=never, overrides --paging option

      --help                             Print help

  -V, --version                          Print version



Filtering Options:

  -l, --level     Filter messages by level [env: HL_LEVEL=]

      --since 



Output Options:

      --color []        Color output control [env: HL_COLOR=] [default: auto] [possible values: auto, always, never]

  -c                          Handful alias for --color=always, overrides --color option

      --theme          Color theme [env: HL_THEME=] [default: universal]

  -r, --raw                   Output raw source messages instead of formatted messages, which can be useful for applying filters and saving results in their original format

      --no-raw                Disable raw source messages output, overrides --raw option

      --raw-fields            Output field values as is, without unescaping or prettifying

  -h, --hide             Hide or reveal fields with the specified keys, prefix with ! to reveal, specify '!*' to reveal all

      --flatten         Whether to flatten objects [env: HL_FLATTEN=] [default: always] [possible values: never, always]

  -t, --time-format   Time format, see https://man7.org/linux/man-pages/man1/date.1.html [env: HL_TIME_FORMAT=] [default: "%b %d %T.%3N"]

  -Z, --time-zone         Time zone name, see column "TZ identifier" at https://en.wikipedia.org/wiki/List_of_tz_database_time_zones [env: HL_TIME_ZONE=] [default: UTC]

  -L, --local                 Use local time zone, overrides --time-zone option

      --no-local              Disable local time zone, overrides --local option

  -e, --hide-empty-fields     Hide empty fields, applies for null, string, object and array fields only [env: HL_HIDE_EMPTY_FIELDS=]

  -E, --show-empty-fields     Show empty fields, overrides --hide-empty-fields option [env: HL_SHOW_EMPTY_FIELDS=]

      --input-info   Show input number and/or input filename before each message [default: auto] [possible values: auto, none, full, compact, minimal]

  -o, --output          Output file



Input Options:

      --input-format        Input format [env: HL_INPUT_FORMAT=] [default: auto] [possible values: auto, json, logfmt]

      --unix-timestamp-unit   Unix timestamp unit [env: HL_UNIX_TIMESTAMP_UNIT=] [default: auto] [possible values: auto, s, ms, us, ns]

      --allow-prefix                Allow non-JSON prefixes before JSON messages [env: HL_ALLOW_PREFIX=]

      --delimiter        Log message delimiter, [NUL, CR, LF, CRLF] or any custom string



Advanced Options:

      --interrupt-ignore-count   Number of interrupts to ignore, i.e. Ctrl-C (SIGINT) [env: HL_INTERRUPT_IGNORE_COUNT=] [default: 3]

      --buffer-size           Buffer size [env: HL_BUFFER_SIZE=] [default: "256 KiB"]

      --max-message-size      Maximum message size [env: HL_MAX_MESSAGE_SIZE=] [default: "64 MiB"]

  -C, --concurrency              Number of processing threads [env: HL_CONCURRENCY=]

      --shell-completions    Print shell auto-completion script and exit [possible values: bash, elvish, fish, powershell, zsh]

      --man-page                    Print man page and exit

      --list-themes                 Print available themes and exit

      --dump-index                  Print debug index metadata (in --sort mode) and exit

      --debug                       Print debug error messages that can help with troubleshooting

```



## Performance



![performance chart](doc/performance-chart.svg)



* MacBook Pro (16-inch, 2021)

    * **CPU**:   Apple M1 Max CPU

    * **OS**:    macOS Sonoma 14.4.1

    * **Data**:  ~ **2.3 GiB** log file, **6 000 000** lines

        * [hl](https://github.com/pamburus/hl) **v0.28.0** ~ *1.4 seconds*

            ```

            $ time hl example.log -c -o /dev/null

            hl example.log -c -o /dev/null  11.74s user 0.53s system 885% cpu 1.386 total

            ```

        * [hlogf](https://github.com/ssgreg/hlogf) **v1.4.1** ~ *8.5 seconds*

            ```

            $ time hlogf example.log --color always >/dev/null

            hlogf example.log --color always > /dev/null  6.93s user 1.79s system 99% cpu 8.757 total

            ```

        * [humanlog](https://github.com/humanlogio/humanlog) **v0.7.6** ~ *77 seconds*

            ```

            $ time humanlog /dev/null

            humanlog> reading stdin...

            humanlog --color always < example.log > /dev/null  80.02s user 4.71s system 109% cpu 1:17.11 total

            ```

        * [fblog](https://github.com/brocode/fblog) **v4.9.0** ~ *36 seconds*

            ```

            $ time fblog example.log >/dev/null

            fblog example.log > /dev/null  32.48s user 2.03s system 97% cpu 35.526 total

            ```



        * [fblog](https://github.com/brocode/fblog) with `-d` flag **v4.9.0** ~ *148 seconds*

            ```

            $ time fblog -d example.log >/dev/null

            fblog -d example.log > /dev/null  132.12s user 14.39s system 99% cpu 2:27.61 total

            ```

    * See [#132](https://github.com/pamburus/hl/issues/132) for how to repeat measurements



[ci-img]: https://github.com/pamburus/hl/actions/workflows/ci.yml/badge.svg

[ci]: https://github.com/pamburus/hl/actions/workflows/ci.yml

[cov-img]: https://codecov.io/gh/pamburus/hl/graph/badge.svg?token=464MN13408

[cov]: https://codecov.io/gh/pamburus/hl