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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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hl Build Status Coverage Status

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 of the less pager by default for convenience.
  • Log streaming with the -P flag that disables the pager.
  • Log record filtering by field key/value pairs with the -f option with support for hierarchical keys.
  • Quick and easy filtering by level with the -l option.
  • Quick and easy filtering by timestamp 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 of fields with the -h option.
  • Hide empty fields with the -e flag.
  • Lightning fast message sorting 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 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 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 file and environment variables, supports easy theme switching and custom themes.

Performance comparison chart

Performance comparison with humanlog, hlogf and fblog on a 2.3 GiB log file

performance chart

Installation options

  • Install using homebrew 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 on Arch Linux

    yay -S hl-log-viewer-bin
  • Install using cargo

    cargo install --locked --git https://github.com/pamburus/hl.git
  • Download latest release from download page

Examples

Screenshot

screenshot-light screenshot-dark

See other screenshots

Features and usage

Concatenation of multiple log files

  • Concatenate all log files

    Command

    hl *.log

    Concatenates and displays all *.log files found in the current directory.

Support for compressed (bzip2, gzip, xz, zstd) log files

  • Concatenate all log files including compressed log files

    Command

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

    Concatenates and displays all *.log, *.log.gz, *.log.zst and *.s (will detect compression) files found in /var/log/example/.

Automatic usage of pager

  • Use the default pager with the default parameters

    Command

    hl example.log

    Automatically opens less pager with the 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="most -w" hl example.log

    Opens most pager with -w option.

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

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

Environment variables 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

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 tool can be used like this:

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

      elements:
          <element>:
              foreground: <color>
              background: <color>
              modes: [<mode>, <mode>, ...]
      levels:
          <level>:
              <element>:
                  foreground: <color>
                  background: <color>
                  modes: [<mode>, <mode>, ...]
    • 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

Alacritty

  • One Dark Neo
    • Note: It is recommended to use draw_bold_text_with_bright_colors: true setting
  • Light
    • 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 <FILE>                    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 <N>                         Number of last messages to preload from each file in --follow mode [default: 10]
      --sync-interval-ms <MILLISECONDS>  Synchronization interval for live streaming mode enabled by --follow option [default: 100]
      --paging <WHEN>                    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 <LEVEL>    Filter messages by level [env: HL_LEVEL=]
      --since <TIME>     Filter messages by timestamp >= <TIME> (--time-zone and --local options are honored)
      --until <TIME>     Filter messages by timestamp <= <TIME> (--time-zone and --local options are honored)
  -f, --filter <FILTER>  Filter messages by field values [k=v, k~=v, k~~=v, 'k!=v', 'k!~=v', 'k!~~=v'] where ~ does substring match and ~~ does regular expression match
  -q, --query <QUERY>    Filter using query, accepts expressions from --filter and supports '(', ')', 'and', 'or', 'not', 'in', 'contain', 'like', '<', '>', '<=', '>=', etc

Output Options:
      --color [<WHEN>]        Color output control [env: HL_COLOR=] [default: auto] [possible values: auto, always, never]
  -c                          Handful alias for --color=always, overrides --color option
      --theme <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 <KEY>            Hide or reveal fields with the specified keys, prefix with ! to reveal, specify '!*' to reveal all
      --flatten <WHEN>        Whether to flatten objects [env: HL_FLATTEN=] [default: always] [possible values: never, always]
  -t, --time-format <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 <TZ>        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 <VARIANT>  Show input number and/or input filename before each message [default: auto] [possible values: auto, none, full, compact, minimal]
  -o, --output <FILE>         Output file

Input Options:
      --input-format <FORMAT>       Input format [env: HL_INPUT_FORMAT=] [default: auto] [possible values: auto, json, logfmt]
      --unix-timestamp-unit <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 <DELIMITER>       Log message delimiter, [NUL, CR, LF, CRLF] or any custom string

Advanced Options:
      --interrupt-ignore-count <N>  Number of interrupts to ignore, i.e. Ctrl-C (SIGINT) [env: HL_INTERRUPT_IGNORE_COUNT=] [default: 3]
      --buffer-size <SIZE>          Buffer size [env: HL_BUFFER_SIZE=] [default: "256 KiB"]
      --max-message-size <SIZE>     Maximum message size [env: HL_MAX_MESSAGE_SIZE=] [default: "64 MiB"]
  -C, --concurrency <N>             Number of processing threads [env: HL_CONCURRENCY=]
      --shell-completions <SHELL>   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

  • 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 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 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 v0.7.6 ~ 77 seconds

        $ time humanlog <example.log --color always >/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 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 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 for how to repeat measurements